The specimen, measuring an impressive 2580 millimeters in total length, was caught by a surface tuna gillnet operated from a multiday fishing boat off the western coastal waters of Sri Lanka on 27 October 2021. The fish was landed at Beruwala Fishery Harbor and subsequently preserved in 5% formaldehyde before being deposited in the National Faunal Repository at the Colombo National Museum, Sri Lanka. This single, fresh, complete specimen now represents the first detailed morphological description of R. russellii from Sri Lankan waters.

Oarfishes, belonging to the family Regalecidae, are among the most extraordinary creatures in the ocean. Characterized by an extremely slender, laterally compressed, and very elongated ribbon-like body, they hold the distinction of being the longest bony fish in the world. The family is classified into just two genera, Regalecus and Agrostichthys, with three known species: Agrostichthys parkeri, Regalecus glesne, and Regalecus russellii. These oceanic fishes occur from surface waters to greater depths in temperate and tropical waters, yet they are exceptionally rare in nature, making every confirmed sighting scientifically significant.

The limited number of sightings, incomplete notes on encounters, scarce voucher specimens, and frequent misidentifications have all contributed to inadequate knowledge about the diversity, taxonomy, ecology, and distribution of oarfish species. This scarcity of information makes the Sri Lankan specimen particularly valuable, as it allows researchers to conduct a thorough morphological analysis that can be compared with confirmed records from other ocean basins.

The research team employed rigorous morphological methodologies to document the specimen. Measurements were collected to 1 millimeter precision using calibrated tape and Vernier calipers, while the specimen’s weight was measured to the nearest gram using a digital weighing balance. The fish was radiographed by dividing it into six overlapping sections using a static X-ray machine at the Faculty of Veterinary Medicine and Animal Science, University of Peradeniya. The X-radiograph images of all six sections were then processed to create a complete image, enabling researchers to count vertebrae and examine the dorsal fin ray arrangement.

The morphological examination revealed fascinating details about the specimen. The dorsal fin contained 337 total soft dorsal rays, with two distinctive dorsal crests: the first crest bearing five rays united by fin membranes and the second crest consisting of a single ray free from other rays. The body was long, deeply compressed, and ribbon-like, tapering towards the tail without scales but covered with dermal tubercles with circular bases. These tubercles became more prominent towards the tail end and lower sides of the body. The head was small, measuring just 9.1% of total length, with an almost vertical profile prior to the dorsal fin origin. The mouth was small, vertical, and protractible, with teeth entirely absent.

The coloration of the fresh specimen was equally striking. The body displayed a silvery-grey base with amorphous oblique dark streaks and blotches distributed across the body, most distinct in the first third. The forehead, mouth, preopercle, opercle, and lower margin of the head appeared greyish black. Perhaps most notably, the upper and lower body margins exhibited a crimson red luster, especially in the first half of the body, while the dorsal and ventral fins were entirely dark crimson red. When preserved, the body coloration shifted to yellowish brown with the same dark streaks and blotches.

The morphological characters of the Sri Lankan specimen matched well with key identification features of R. russellii previously reported from the eastern and western Pacific Ocean and the Atlantic Ocean. This consistency across ocean basins provides important confirmation of the species’ identity and extends its known range into the northern tropical Indian Ocean. The vertebral count of 114 and the gill raker arrangement on the first gill arch, numbering 55 in total with 12 on the upper portion and 43 on the lower, further supported the identification.

The significance of this record extends beyond simple range extension. Regalecus russellii was originally described as Gymnetrus russelii by Cuvier in 1816 from Vizagapatam, now Visakhapatnam, on the eastern coast of India in the Bay of Bengal. The first documentation of a Regalecus species from the Indian Ocean actually dates back to 1788, when Patrick Russell recorded a specimen from Visakhapatnam, though that juvenile specimen was not retained after drawing. Despite numerous scattered records of Regalecus from the Indian Ocean over the centuries, only two specimens had been identified to species level as R. russellii prior to this report, and no single specimen from the Indian Ocean has been accepted as a neotype for the species.

The two Regalecus species exhibit contrasting distribution patterns across the world’s oceans. In the Pacific Ocean, numerous records of R. russellii are documented from the North Pacific, while all records of R. glesne are concentrated in the South, with the exception of one R. russellii record from northern New Guinea. In the Atlantic Ocean, R. glesne has been documented exclusively in the North Atlantic and Mediterranean, while both species occur in the South Atlantic. The two species also show distinct habitat preferences related to water temperature and ocean currents: R. glesne is typically associated with colder waters, whereas R. russellii is commonly found in warmer regions. The Sri Lankan record, coming from the warm tropical waters of the northern Indian Ocean, aligns perfectly with these thermal preferences.

Interestingly, the spawning grounds of both Regalecus species occur at the extreme western end of the Indian Ocean, on the southern coast of South Africa, with R. glesne spawning also documented at the eastern end of the Indian Ocean on the coast of Western Australia. According to Roberts, the adults and early life stages of Regalecus found on the south coast of South Africa could be part of populations from the South Atlantic. The presence of a mature specimen in Sri Lankan waters raises intriguing questions about whether resident populations exist in the northern Indian Ocean or whether individuals occasionally venture far from known population centers.

The association of Regalecus with upwelling zones is particularly noteworthy. These areas feature surface cold water rich in biological productivity, which can serve as feeding grounds with optimum environmental conditions close to surface waters. The present specimen was found in shallow waters off the western coast of Sri Lanka, an area that overlaps with the coastal upwelling region. Numerous mesopelagic fish species, including members of the family Trachipteridae, have been recorded from the western and southern coastal upwelling zones of Sri Lankan waters during the summer monsoon, suggesting these productive areas attract deep-water species towards the surface.

Most records of Regalecus species are accidentally caught in fishing gear during operations and are often discarded without proper documentation. There have been many reports of oarfish landings by fishermen at various sites along the Indian and Sri Lankan coastal waters, but many of these accounts have not been published in peer-reviewed publications or made accessible to the scientific community. Advancing technology, along with the widespread accessibility of cameras and smartphone cameras, has significantly improved the frequency of recordings in recent years within the Indian Ocean region.

Citizen science programs and knowledge dissemination platforms, including social media, apps, and websites, play a crucial role in enhancing public awareness and encouraging the recording of rare or poorly known marine species. Such programs are essential to understanding marine biodiversity and supporting conservation strategies, particularly in understudied tropical waters. The Sri Lankan oarfish record demonstrates how collaboration between fishermen, researchers, and natural history institutions can yield significant scientific discoveries, even in an era of advanced marine research technology.

Seasonal patterns in Regalecus strandings and accidental catch records have been observed in certain areas, such as the Gulf of Mexico coast of Florida, though these events have not been clearly linked to environmental factors. In contrast, stranding and accidental catch reports from Australian waters have shown a clear association with storm events. The few records of Regalecus from the Indian Ocean remain inadequate to observe any patterns of stranding or accidental catch, but the species recorded are closely associated with upwelling zones of the Indian Ocean. As more records accumulate from this vast and understudied region, researchers may begin to identify environmental drivers behind these encounters.

This first confirmed record of Regalecus russellii from Sri Lankan waters represents a milestone in Indian Ocean marine biology. The detailed morphological description, complete with radiographic analysis and comprehensive meristic data, provides a reference point for future identifications in the region. The specimen, now safely preserved in the National Faunal Repository at the Colombo National Museum, stands as a testament to the scientific value of even a single well-documented specimen. As technology continues to advance and more researchers and citizens turn their attention to the ocean’s mysteries, the veil surrounding these magnificent ribbon-like giants of the deep may finally begin to lift, revealing insights into their biology, distribution, and the ecological roles they play in the vast tropical Indian Ocean.

Subject of Research: First record of oarfish, Regalecus russellii (Actinopterygii, Lampriformes, Regalecidae), from Sri Lankan waters, Indian Ocean

Article Title: First record of oarfish, Regalecus russellii ( Actinopterygii , Lampriformes , Regalecidae ), from Sri Lankan waters, Indian Ocean

Article References: Rathnasuriya, M. I. G., & Hapuarachchi, T. H. I. S. (2025). First record of oarfish, Regalecus russellii (Actinopterygii, Lampriformes, Regalecidae), from Sri Lankan waters, Indian Ocean. Acta Ichthyologica et Piscatoria, 55, 145-150. https://doi.org/10.3897/aiep.55.148496

Image Credits: AI Generated

DOI: 10.3897/aiep.55.148496

Keywords: oarfish, Regalecus russellii, Sri Lanka, Indian Ocean, marine biology, deep sea, rare species, fish taxonomy, upwelling zones, marine biodiversity, First, record

Nematodes are the fourth most speciose animal phylum, with roughly 25,000 described species, and by sheer numbers of individuals they are the most abundant animal group on the planet, accounting for around one percent of total animal biomass. They thrive in nearly every ecosystem on Earth, from polar sediments to agricultural soils, occupying niches that range from free-living grazers to parasites of plants and animals. In marine environments, free-living nematodes are generally the most speciose component of the meiofauna, the community of microscopic animals living between sediment grains. Their ubiquity and sensitivity to environmental conditions also make them valuable bioindicators, capable of signaling the health of estuarine and marine ecosystems long before changes become visible at larger scales.

To assess what is actually known about Costa Rica’s marine nematodes, the researchers systematically searched the scientific literature and four international biodiversity databases: the Ocean Biodiversity Information System (OBIS), the Global Biodiversity Information Facility (GBIF), Nemys, the world database of nematodes, and the World Register of Marine Species (WoRMS). From each publication they extracted the level of taxonomic identification, the sampling locality, and the year of collection. The search revealed just fourteen papers mentioning marine nematodes from Costa Rica, and of those, only three included any taxonomic detail at all. The remaining eleven treated nematodes simply as a group, reporting their abundance without identifying a single species.

The geographic pattern of this sparse record is equally telling. Thirteen of the fourteen publications concern the Pacific coast, while only one, a 1974 study of sandy beach infauna by Dexter, touches the Caribbean side. All ten identified species were found on the Pacific coast, and five of the free-living species were described in a single burst of taxonomy more than a century ago, by the nematologist Cobb in 1920, from samples collected at Puntarenas. No nematode data exist for Caribbean seagrass beds or coral reefs, and sampling on the Caribbean sandy beaches has been so limited that Dexter reported nematodes at only one of five Caribbean beaches surveyed, compared with one of eight Pacific beaches.

The five free-living species described by Cobb, Antomicron pellucidum, Hypodontolaimus punctulatus, Pseudochromadora quadripapillata, Pseudolella cephalata, and Zygonemella striata, have had complicated taxonomic histories. A. pellucidum, the type species of its genus, remains valid even though the illustrations in the original description are considered insufficient for comparison, and remarkably, a specimen later studied in the Gulf of Mexico off Florida was assigned to this species originally described from the Pacific coast of Costa Rica. P. quadripapillata has accumulated multiple synonyms and has been reported from locations as distant as Belize, Canada’s Bay of Fundy, the Maldives, Brazil, New Guinea, and Australia, with some databases even listing freshwater as a plausible habitat. Z. striata, the sole species of its genus, was recently matched by Operational Taxonomic Units in Antarctic sediments through DNA metabarcoding, with sequence identity above ninety percent, hinting at a distribution far broader than the historical record suggests.

The parasitic side of the record is equally thin but medically and ecologically significant. The most recent free-living-adjacent description is Echinocephalus janzeni, a parasite described in 1998 from the intestine of a Pacific sting ray, based on specimens collected in Costa Rica and Mexico. The remaining parasitic records come from stranded marine mammals: unidentified species of Anisakis, the genus responsible for human anisakiasis, have been recovered from the digestive tracts of striped, pantropical spotted, and spinner dolphins and Cuvier’s beaked whale. Crassicauda anthonyi, a kidney parasite that can be fatal, was found in a stranded Cuvier’s beaked whale, and nematodes of the genus Halocercus, including H. lagenorhynchi, were collected from the lungs and air passages of pantropical spotted dolphins. Four additional parasitic taxa were reported from stranded cetaceans in 2023, underscoring how much parasite diversity likely remains undocumented.

Where taxonomic identification is absent, abundance data still reveal how dominant nematodes can be. Studies of intertidal mud flats in the Gulf of Nicoya in the mid-1980s found nematodes comprising between 74.9 and 88.1 percent of total organisms, with vertical distribution analyses showing that over 82 percent of individuals concentrated in the top two centimeters of sediment. On coral reefs at Isla del Caño Biological Reserve, nematodes represented about 19 percent of sediment fauna. Around Isla del Coco, a remote oceanic island, nematodes were the second most abundant group at 24 of 27 sampling stations, totaling more than 3,300 individuals, yet every specimen was logged simply as unidentified Adenophorea, a broad subclass, with no species-level resolution.

Perhaps the most dramatic numbers come from deep water. A study of meiofauna along the central Pacific coast at depths of 400 and 1,800 meters found nematodes averaging nearly 80 percent of total abundance, peaking at 99.9 percent within the Oxygen Minimum Zone at 400 meters. The nematode density recorded there, roughly 3,688 individuals per ten square centimeters, is the highest reported for any oxygen minimum zone in the eastern Pacific, even though species richness in that zone was among the lowest. At a methane seep near Mound 12 at about 1,000 meters depth, nematodes made up nearly 10 percent of the meio-epifaunal organisms colonizing deployed woodblocks, and were more abundant on wood at inactive seep sites than at active ones.

The review’s authors emphasize that this scarcity of taxonomic data is not a reflection of the group’s true diversity. Comparable tropical ecosystems elsewhere tell a very different story: a single study of Cuban seagrass beds identified 215 nematode species across 138 genera, 35 families, seven orders, and two classes. Nematodes are also the most abundant taxon in methane seeps of the Gulf of Cádiz, and Costa Rica’s Pacific margin hosts numerous methane seeps of its own. On the parasitic front, Mediterranean studies have documented nematodes in edible scallops and in sea turtles such as the loggerhead, hosts that also occur in Costa Rican waters, suggesting similar or identical parasites await discovery there.

The message of the review is a call to action for tropical marine taxonomy. Because nematodes are simultaneously the most abundant meiofaunal group, sensitive indicators of environmental quality, and key players in sediment food webs, the near-total absence of species-level data from Costa Rica represents a significant gap in understanding the country’s marine biodiversity. The authors argue that dedicated taxonomic effort, combining classical morphology with modern molecular tools, is needed to explore the actual diversity of marine nematodes on both coasts, in habitats ranging from sandy beaches and mud flats to coral reefs, oxygen minimum zones, and deep-sea seeps. Until that work is done, the microscopic majority of Costa Rica’s marine fauna will remain, quite literally, unnamed.

Subject of Research: Diversity and taxonomy of marine nematodes in Costa Rica

Article Title: Marine nematodes of Costa Rica: state of the art

Article References: Sánchez-Monge, A., & Cortés, J. (2024). Marine nematodes of Costa Rica: state of the art. Neotropical Biology and Conservation, 19(2), 319-331. https://doi.org/10.3897/neotropical.19.e115345

Image Credits: AI Generated

DOI: 10.3897/neotropical.19.e115345

Keywords: marine nematodes, Costa Rica, meiofauna, taxonomy, biodiversity, bioindicators, oxygen minimum zone, parasitic nematodes, Pacific coast, Caribbean coast, deep sea, Neotropics

The discovery was made during a biodiversity survey of seamounts near the Mariana Trench, an area of the tropical western Pacific renowned for its vibrant and poorly explored ecosystems. Using the research vessel KEXUE and the remotely operated vehicle FAXIAN, the team collected a single amphipod specimen from a depth of 779.6 meters on a seamount tentatively named M2. Remarkably, the specimen was found in association with a deep-sea sponge of the genus Semperella, a partnership that would later inspire the species’ whimsical name.

Detailed morphological examination under a ZEISS Discovery V20 microscope revealed a crustacean unlike any of the 414 known maerid species. The animal, an elongate, laterally compressed brooding female measuring 9.3 millimeters, lacks eyes entirely, a common trait in deep-sea species but unusual among maerids, most of which inhabit sunlit shallow waters. Its mandible is missing the molar, a grinding structure present in most of its relatives. The inner plate of its first maxilla bears only a single apical plumose seta, and the inner and outer plates of its maxilliped are dramatically reduced. Perhaps most strikingly, the inner ramus of its third uropod carries long plumose setae, giving it a feathery appearance unlike anything else in the family.

These characters, in combination, are so unique that the researchers erected a new genus, Renomaera, to accommodate the species. The genus name honors retired Professor Xianqiu Ren of the Institute of Oceanology, Chinese Academy of Sciences, for his contributions to Chinese carcinology, combined with the family name Maeridae. The species name, patricki, is a nod to Patrick Star from the cartoon SpongeBob SquarePants, because Patrick is SpongeBob’s best friend and this new species was collected in association with a sponge.

But the discovery is more than a taxonomic curiosity. To understand where Renomaera patricki fits in the evolutionary history of amphipods, the team turned to molecular phylogenetics, sequencing one mitochondrial gene, cytochrome c oxidase subunit I (COI), and two nuclear genes, histone H3 and 28S ribosomal RNA. Genomic DNA was extracted from an intra-marsupial individual held by the holotype female, sequenced using Illumina HiSeq technology, and assembled de novo using SPAdes version 4.0.0. The resulting sequences were aligned with MAFFT, trimmed with trimAL, and concatenated using SequenceMatrix before phylogenetic trees were constructed using both maximum likelihood and Bayesian inference methods.

The results were startling. In both data sets, the analyses strongly rejected the monophyly of Maeridae, meaning the family, as currently defined, does not consist of a single evolutionary lineage descended from a common ancestor. This is a fundamental challenge to the classification of a group encompassing 49 genera and 414 species, distributed from the intertidal zone to depths exceeding 7,000 meters. The family was originally established in 2008 based on the morphology of the third uropod, which has rami of subequal length, but the new molecular evidence suggests this single character is not a reliable indicator of shared ancestry.

The phylogenetic trees also revealed that the Maera clade, one of three groups originally recognized within Maeridae, is itself non-monophyletic. Renomaera patricki clustered with four maerid species, including Maera danae from the type genus, with strong support in the first data set. However, other maerid species were scattered across the tree in ways that defied the traditional groupings. The deep-sea species Bathyceradocus hawkingi, for instance, formed a sister group to species from four other families in the maximum likelihood analysis, with strong support, suggesting it may not belong in Maeridae at all.

In contrast, the analyses supported the monophyly of three other families within the superfamily Hadzioidea: Metacrangonyctidae, Melitidae, and Eriopisidae. The Elasmopus group, characterized by well-developed eyes and a short accessory flagellum, was also supported as a natural group. But the Ceradocus group could not be verified because only one species was included in the analyses. The superfamily Hadzioidea is vast, and the relatively few species and genera sampled in this study mean that a comprehensive understanding of relationships within it will require far more taxonomic and molecular data.

The discovery of Renomaera patricki is also significant for what it reveals about deep-sea maerid ecology. This is the first time a deep-sea maerid species has been found associated with a sponge. Other deep-sea maerids, representing at least 15 genera, have been recorded from muddy substrates or in association with sunken wood. The association with Semperella suggests that sponges may serve as important habitat structures for deep-sea amphipods, much as they do in shallow waters, and that seamounts, which harbor vibrant biodiversity, may be hotspots of undiscovered maerid diversity.

Based on the new evidence, the researchers propose amending the diagnosis of Maeridae to allow for the absence of a mandibular molar and the presence or absence of long plumose setae on the inner ramus of the third uropod. The holotype specimen, a brooding female carrying 13 intra-marsupial young, is deposited in the Marine Biological Museum of the Chinese Academy of Sciences in Qingdao, China. As exploration of the deep sea continues, and as molecular tools become ever more powerful, it is likely that more species like Renomaera patricki will emerge from the shadows, each one adding a new branch, and sometimes a new trunk, to the tree of life.

Subject of Research: Evolutionary Biology

Article Title: Renomaera patricki gen. et sp. nov. ( Amphipoda , Hadzioidea , Maeridae ) described from the seamount in the western Pacific, with a test of monophyly of Maeridae Krapp-Schickel, 2008

Article References: Sha, Z.-L., & Wang, Y.-R. (2026). Renomaera patricki gen. et sp. nov. (Amphipoda, Hadzioidea, Maeridae) described from the seamount in the western Pacific, with a test of monophyly of Maeridae Krapp-Schickel, 2008. Zoosystematics and Evolution, 102(2), 471-481. https://doi.org/10.3897/zse.102.171557

Image Credits: AI Generated

DOI: 10.3897/zse.102.171557

Keywords: Amphipoda, Deep Sea, Taxonomy, Phylogenetics, Mariana Trench, New Species, Renomaera, patricki, Hadzioidea, Maeridae, described, seamount

The expedition used the human-occupied submersible JiaoLong, launched from the research vessel ShenHai YiHao during cruise DY72, to collect 13 chrysogorgiid specimens from the two ridge systems. Two specimens came from the Carlsberg Ridge in the northern Indian Ocean, while the remaining eleven were gathered from the Ninetyeast Ridge, a vast north-south undersea mountain chain. Every colony was photographed in its natural position on the seafloor before being preserved in 75 percent ethanol, allowing researchers to document both the living appearance and the microscopic anatomy of each animal.

Chrysogorgiidae is a family of octocorals found worldwide in deep-sea environments, currently comprising more than 100 species in seven valid genera. Nearly all of its members are restricted to deep-sea habitats, and the family includes the genera Chrysogorgia, Iridogorgia, Metallogorgia, Radicipes, Parachrysogorgia, Pseudochrysogorgia, and Ramuligorgia. Yet despite this global distribution, most recorded species have come from the Atlantic and Pacific Oceans, with only a handful of reports from the Indian Ocean, particularly from its ridge regions. This gap in taxonomic and genetic data has long hindered understanding of how Indian Ocean populations connect to those in other oceans.

The first new species, Chrysogorgia pugnioides Ge, Hu and Xu, sp. nov., was collected from the Guangde Ridge at a depth of 2,674 meters. Its name derives from the Latin adjective pugnioides, meaning fist-shaped, a reference to the remarkable appearance of its polyps, which resemble clenched fists when their tentacles contract. The holotype colony is bottlebrush-shaped, about 58 centimeters long and 20 centimeters wide, with a brown stem bearing an aeruginous metallic luster. Under the microscope, the species reveals warty spindles in the tentacles, flat and irregular spindles and elongate scales in the polyp body wall, and slender, smooth scales with toothed to irregular edges in the coenenchyme, the tissue connecting the branches.

The second and third new species belong to the genus Iridogorgia, famous for its upward-spiraling axes with brilliant iridescence and unbranched branches arising from one side. Iridogorgia acutisclerita Ge, Zhang and Xu, sp. nov., collected from the Ninetyeast Ridge at depths between 1,897 and 1,977 meters, builds closely coiled helices up to 73 centimeters tall, with 12 helical turns each roughly 6 centimeters in height. Its name combines the Latin acutus, meaning sharp, with the Greek skleros, meaning hard, referring to the characteristic sclerites, the tiny calcified structural elements that all feature two sharp ends. The species resembles I. splendens in colony form but differs by possessing needles and pointed elongate scales in the polyp body wall.

Iridogorgia levisquama Ge, Zhang and Xu, sp. nov., also from the Ninetyeast Ridge at a depth of 2,073 meters, is an even more dramatic animal. Its holotype colony stands approximately 120 centimeters tall, with six loosely coiled helical turns each 18 centimeters in height, growing counterclockwise on a calcareous holdfast about 6.5 centimeters in diameter. The name derives from the Latin levis, meaning smooth, and squama, meaning scale, referring to the nearly smooth scales in the basal part of the polyp body wall. It is differentiated from its congener I. squarrosa by slender, smooth scales with sharp ends in the polyp body wall and needles with fine wartiness in the tentacles.

Beyond the three new species, the team reported two known species as new records for the Indian Ocean ridges. Parachrysogorgia chryseis, previously known from the Pacific Ocean including the Indonesian Ceram Sea and seamounts on the Caroline Ridge, was collected from the Carlsberg Ridge at 1,700 meters, where it grew as a bi-flabellate yellow colony on the white branch of a dead coral. Metallogorgia melanotrichos, first described from Ascension Island in the South Atlantic and recorded across the central Indo-Pacific, western and central Pacific, and Atlantic, was found at six sites on the Ninetyeast Ridge at depths between 1,976 and 2,073 meters. Notably, nearly all M. melanotrichos specimens hosted the same ophiuroid species, Ophiocreas oedipus, consistent with North Atlantic records and supporting a highly specific epibiotic association between the two species.

To confirm the new species, the researchers integrated morphological examination with molecular phylogenetic analysis using two genetic markers: the partial mitochondrial mutS homolog, known as mtMutS, and the nuclear 28S ribosomal DNA region. Tissues were digested to isolate the microscopic sclerites, which were then examined under a Regulus 8100 scanning electron microscope after gold-coating. DNA was extracted from polyps and amplified by polymerase chain reaction, with sequences aligned in MAFFT and trimmed to conserved blocks using Gblocks. Phylogenetic trees were constructed using both maximum likelihood and Bayesian inference algorithms, with the mtMutS dataset comprising 85 chrysogorgiid sequences and the 28S rDNA dataset comprising 58, each with keratoisidid outgroups.

The genetic results strongly support the validity of all three new species. In the 28S rDNA phylogeny, Chrysogorgia pugnioides formed a distinct, well-supported lineage as the sister group to a clade containing C. pinniformis, C. cylindrata, C. pendula, and C. acanthella. Iridogorgia acutisclerita formed a well-supported clade, while I. levisquama was recovered as a strongly supported independent lineage sister to I. squarrosa. Genetic distance analyses showed that the new species diverge from their congeners by measurable margins, with C. pugnioides differing from other Chrysogorgia species by 1.53 to 8.22 percent in 28S rDNA. Interestingly, the two new Iridogorgia species were genetically identical to some congeners in mtMutS, highlighting the value of combining both markers, since rate heterogeneity between mitochondrial and nuclear gene evolution in octocorals can produce different topologies.

Perhaps most significantly, the two new Iridogorgia species represent the first confirmed taxonomic records of this genus in the Indian Ocean. Iridogorgia previously comprised 14 valid species concentrated in three high-diversity regions: the tropical western Pacific with 10 species, the waters around Hawaii with five, and the Northwest Atlantic with five. Although recent remotely operated vehicle surveys documented Iridogorgia in the Perth Canyon of the southeastern Indian Ocean, those observations had never been formally described. The establishment of these two new species validates the occurrence of Iridogorgia in the northern Indian Ocean and significantly expands its known biogeographic range beyond the traditional diversity centers of the Pacific and Atlantic. Together with the new records of Parachrysogorgia chryseis and Metallogorgia melanotrichos, the study suggests the Indian Ocean Ridge system may represent an overlooked diversity hotspot for Chrysogorgiidae, providing a foundation for future biogeographic and evolutionary studies of deep-sea octocorals in this region.

Subject of Research: Systematics and biogeography of Chrysogorgiidae from the Indian Ocean: discovery of new species on deep-sea ridges

Article Title: Systematics and biogeography of Chrysogorgiidae from the Indian Ocean: discovery of new species on deep-sea ridges

Article References: Ge, M., Xu, N., Hu, X., Tian, X., Li, X., Xu, Y., Wang, Z., Zhang, X., & Xu, Q. (2026). Systematics and biogeography of Chrysogorgiidae from the Indian Ocean: discovery of new species on deep-sea ridges. Zoosystematics and Evolution, 102(2), 621-647. https://doi.org/10.3897/zse.102.182492

Image Credits: AI Generated

DOI: 10.3897/zse.102.182492

Keywords: Systematics, biogeography, Chrysogorgiidae, Indian, Ocean, discovery, species, deep-sea, ridges, scientific research

The research team, led by scientists working on deep-sea echinoderms, sequenced the mitochondrial genomes of four brittle star species collected from deep-sea environments: Ophioctenella acies, a hydrothermal vent dweller; Ophiura cf. irrorata and Ophiactis profundi, both from non-reduced deep-sea habitats; and Ophiocreas nudusoralis. Notably, the mitochondrial genome of O. acies represents the first ever reported from a hydrothermal vent ophiuroid, filling a significant gap in our understanding of how life thrives at these chemically extreme undersea hot springs.

Mitochondrial genomes are compact circular DNA molecules inherited maternally, making them powerful tools for reconstructing evolutionary relationships. Using next-generation sequencing on an Illumina NovaSeq 6000 platform, the researchers extracted genomic DNA from specimens preserved in ethanol, assembled the circular mitogenomes with the NOVOPlasty assembler, and annotated them with the MITOS2 toolset. The four new genomes ranged in length from 15,850 to 16,326 base pairs and contained the standard set of 37 mitochondrial genes, including 13 protein-coding genes, two ribosomal RNA genes, and 22 transfer RNA genes.

With these new sequences in hand, the team employed maximum likelihood and Bayesian inference approaches to reconstruct the phylogeny of the entire class. The resulting trees, generated independently by three different methods, consistently supported the monophyly of the two major clades within Ophiuroidea, Ophintegrida and Euryophiurida, as well as the four major orders: Ophiurida, Euryalida, Amphilepidida, and Ophiacanthida. This is a significant achievement, as the monophyly of Amphilepidida and Ophiacanthida had remained controversial in previous analyses, with different datasets and methods yielding up to nine distinct topologies among 18 generated trees in earlier work.

The improved phylogenetic resolution also clarified previously unstable family-level relationships. Within Euryalida, the study confirmed that Asteronychidae clusters with Gorgonocephalidae rather than occupying a basal position, consistent with some prior molecular studies. Within Ophiurida, the relationships among species in the families Ophiuridae and Ophiopyrgidae remain complicated, with the genus Ophiura showing some conflicts with earlier classifications. The authors suggest that an integrated review combining morphological and molecular evidence is urgently needed to fully resolve these remaining uncertainties.

Beyond phylogeny, the study delved into the temporal history of brittle star evolution. Using BEAST software with seven fossil-based calibration points and an uncorrelated relaxed molecular clock, the researchers estimated that the common ancestor of all Ophiuroidea originated around the Permian-Triassic boundary, approximately 255 million years ago, coinciding with the most severe mass extinction event in Earth’s history. The four major orders radiated at different times: Ophiacanthida and Amphilepidida emerged during the Triassic, Ophiurida during the Jurassic, and Euryalida more recently in the Cretaceous.

The ancestral state reconstruction revealed a fascinating pattern of bidirectional habitat transitions between shallow and deep waters. Ophiacanthida and Euryalida appear to have originated in the deep sea and repeatedly colonized shallow environments, while Ophioleucida and Ophiurida expanded from shallow waters into the deep. These transitions were particularly concentrated during the Jurassic and Cretaceous periods, coinciding with major geological events such as plate tectonic movements, the formation of new marine basins, rising deep-sea temperatures that reduced the thermal gradient between surface and bottom waters, and significant sea level rise. The mid-Cretaceous divergences may be linked to repeated oceanic anoxic events and warm geological intervals that reshaped ocean chemistry and ecology.

One of the most intriguing findings concerns the colonization of chemosynthetic ecosystems, such as hydrothermal vents and cold seeps, which are oases of life in the otherwise food-scarce deep sea. The study found that among four chemosynthetic species analyzed, three experienced significant fluctuations in marine sulfate levels just prior to their divergence, suggesting a possible link between sulfur chemistry and the evolution of vent and seep fauna. The cold-seep species Histampica haimaensis was the first to diverge in the mid-Jurassic, followed by Amphiura sp. in the early Cretaceous, while Ophiophthalmus serratus and Ophioctenella acies diverged in the early Paleogene.

When the researchers examined adaptive evolution at the molecular level, they found a surprising contrast between the hydrothermal vent species and the cold-seep species. The three cold-seep brittle stars showed clear evidence of mitochondrial gene rearrangements and positive selection on specific genes, including ATP6, ATP8, ND2, COX1, and COX2, consistent with adaptive responses to the toxic, oxygen-poor conditions of their environments. However, the hydrothermal vent species O. acies showed no gene rearrangements and no positive selection signals, instead exhibiting the lowest nucleotide substitution rates among the four species, suggesting it may have adapted through strong purifying selection that minimizes the accumulation of harmful mutations rather than through the evolution of new molecular functions.

This finding challenges the assumption that extreme environments universally drive positive selection in mitochondrial genomes and highlights the diversity of evolutionary strategies that organisms can employ when colonizing harsh habitats. The study also revealed that mitochondrial gene rearrangement patterns and selective pressures varied markedly between lineages rather than correlating with habitat type or depth, with the clade Ophintegrida showing higher structural plasticity than the more conserved Euryophiurida. By establishing the most comprehensive mitochondrial genome framework for brittle stars to date, this research provides a robust foundation for future investigations into echinoderm diversification, biogeographic dispersal, and the molecular mechanisms that enable life to flourish in some of the most extreme environments on our planet.

Subject of Research: Mitochondrial genome phylogenetics and deep-sea adaptive evolution of brittle stars (Ophiuroidea)

Article Title: Mitochondrial genomes resolve phylogenetic conflicts and lineage-specific adaptive dynamics in Ophiuroidea : insights from deep-sea lineages

Article References: Xu, W., Na, J., Gao, K., Gu, X., Zhou, Y., Zhang, R., Sun, J., & Zhang, D. (2026). Mitochondrial genomes resolve phylogenetic conflicts and lineage-specific adaptive dynamics in Ophiuroidea: insights from deep-sea lineages. Zoosystematics and Evolution, 102(2), 687-699. https://doi.org/10.3897/zse.102.163746

Image Credits: AI Generated

DOI: 10.3897/zse.102.163746

Keywords: brittle stars, Ophiuroidea, mitochondrial genomes, deep sea, hydrothermal vents, cold seeps, phylogenetics, adaptive evolution, echinoderms, gene rearrangement, positive selection, divergence time

The genus Podosphaeraster currently comprises seven species, all found on the seabed at depths below approximately 70 metres. Their peculiar spherical morphology has made their phylogenetic placement a subject of ongoing debate since they were first described. Early researchers suggested that these animals belonged to Sphaerasteridae, a family originally established for fossil species. However, subsequent detailed skeletal analyses of the fossil forms indicated that the resemblance was likely a result of convergent evolution, leading to the establishment of a separate family, Podosphaerasteridae, within the order Valvatida. The controversy has persisted, with some taxonomists re-instating the genus within Sphaerasteridae and others maintaining the separate family classification. Meanwhile, molecular analyses have revealed that Valvatida itself is likely a large polyphyletic group, meaning its members do not all share a single common ancestor, leaving the taxonomic position of Podosphaeraster still unresolved.

To address this knowledge gap, the researchers conducted a detailed micro-focus X-ray computed tomography examination of the internal skeletal structure of Podosphaeraster toyoshiomaruae, collected from the seas around Japan. One specimen came from the Oshima-shinsone Bank in south-western Japan at depths of 147 to 149 metres, while another, used for morphological observation, was collected between Okinawa-jima Island and Miyako-jima Island at depths of 95 to 100 metres. Both specimens are deposited at the National Museum of Nature and Science in Japan. Concurrently, the team performed shotgun sequencing using next-generation sequencing technology to determine key molecular markers used in previous phylogenetic studies and, remarkably, the complete mitochondrial genome sequence.

The mitochondrial genome of Podosphaeraster toyoshiomaruae was determined to be 16,247 base pairs in length, with a nucleotide composition that is AT-rich at 65.5 percent. The start and stop codons for the 13 protein-coding genes followed patterns common amongst starfish. However, compared to the general gene arrangement known for the broader group of modern starfish, the COX2 gene was found to be translocated in the Podosphaeraster toyoshiomaruae mitogenome, while the arrangement of all other genes, including transfer RNAs, remained identical to the general pattern. This structural rearrangement represents the first evidence of a major protein-coding gene translocation within Asteroidea, the class that contains all starfish. The discovery is particularly striking because mitochondrial gene arrangements in echinoderms are generally highly conserved, although recent mitogenome sequencing has increasingly revealed lineage-specific rearrangements, particularly in brittle stars.

The genetic divergence is mirrored by significant morphological specialisation. The micro-CT scanning, performed at a tube voltage of 115 kilovolts and a tube current of 70 microamperes for 40 minutes, revealed the arrangement and morphology of the skeletal plates in extraordinary detail. The examined specimen had a horizontal diameter of 9.6 millimetres and a vertical diameter of 6.3 millimetres. The apical system was polygonal, located at the abactinal centre and composed of one central, six interradial, five radial and three additional plates. The central plate was oval and surrounded by six elongated interradial plates, while wedge-shaped radial plates were alternately positioned between them. A madreporite, the sieve-like structure through which water enters the water vascular system, was located at the centre of one of the primary interradial plates.

Perhaps the most significant morphological finding concerns the mesentery, the internal membrane that supports the digestive organs. The presence of calcified reinforcement in the mesentery had been previously implied, but the detailed structure of its skeleton is presented for the first time in this study. The micro-CT images revealed that the mesentery skeleton spans the I-plate, an unpaired actinal plate, and connects to the V-plate and five pairs of plates, including three kinds of marginal plates. This observation suggests that the marginal plates of this species may not be homologous with those of other starfish, as the mesentery skeleton in other asteroids is typically contiguous with abactinal and actinal plates and odontophores, but not with marginal plates. In other words, the structures that look like marginal plates in Podosphaeraster may have arisen independently rather than being inherited from a shared ancestor.

Notably, while the connectivity of the mesentery skeleton varies, there is a lack of significant morphological differentiation between the marginal plate series and the adjacent dorsolateral and actinal plates. One researcher has questioned the homology of marginal plates in Podosphaeraster, suggesting that the fossil family Sphaerasteridae evolved from the Mesozoic family Stauranderasteridae through the development of a spherical body and the subsequent loss of differentiated marginal plates. Although varying degrees of marginal plate reduction are shared with the order Velatida, the researchers consider this to be a case of convergent evolution, where similar features arise independently in unrelated lineages due to similar selective pressures rather than shared ancestry.

On the phylogenetic side, the team analysed mitochondrial 12S and 16S rRNA and nuclear histone H3 gene sequences from 117 operational taxonomic units, aligning a total of 345 sequences from the three gene regions. In their resulting phylogenetic tree, the order Valvatida was resolved as polyphyletic, consistent with previous molecular findings. Podosphaeraster toyoshiomaruae was positioned as the most basal lineage within Valvatida, with the family Poraniidae placed adjacent to it. However, this placement received low statistical support in the Maximum Likelihood tree, with a bootstrap value of 63 percent, and no support in the Bayesian Inference tree. The researchers attribute this instability to long-branch attraction, a phylogenetic artefact caused by the excessively rapid evolutionary rate of the sequenced genes in this species, which can make rapidly evolving lineages appear artificially closely related or basal.

The three genetic markers provided poor resolution for the deep phylogeny of starfish higher taxa, likely because their evolutionary rates are too rapid to accurately resolve divergences that occurred approximately 250 million years ago. Substitution saturation tests indicated that the dataset is generally unsaturated at the family level, but the results suggested that saturation may confound relationships amongst specific taxa. The phylogenetic instability is further complicated by ongoing controversy surrounding outgroup selection and root placement in starfish phylogenetics. The researchers provisionally utilised a Velatida clade to root their tree, following previous studies that suggested Velatida resolves basal to Valvatida in molecular analyses. Their resulting topology revealed several discrepancies with previous studies but consistently supported the polyphyly of Valvatida.

To resolve these deep relationships, future studies must employ a larger set of genetic markers with more conservative evolutionary rates. Additionally, discovering extant taxa closely related to the genus Podosphaeraster will be crucial to breaking the long branch and improving phylogenetic accuracy. The researchers also emphasise that more observations of mesenteric skeletons using micro-CT across various Podosphaeraster species will help assess the homology and diversity of skeletal ossicles amongst Podosphaerasteridae taxa. Strictly speaking, the evolutionary origins of the marginal plates remain unknown without comparative evolutionary-developmental studies. For now, this spherical starfish stands as a testament to how much remains to be discovered in the deep sea, where animals with bodies unlike any of their relatives continue to challenge our understanding of how evolution shapes life on Earth. The volumetric image data from the micro-CT reconstruction is openly available at MorphSource, and the genetic sequences are deposited in the DDBJ, EMBL and GenBank databases, ensuring that this enigmatic animal’s secrets remain accessible to researchers worldwide.

Subject of Research: Evolutionary Biology

Article Title: Phylogenetic position of the enigmatic starfish family Podosphaerasteridae ( Asteroidea , Valvatida ) with a morphological observation of the skeletal structure by micro-CT

Article References: Hiruta, S., Kobayashi, I., & Fujita, T. (2026). Phylogenetic position of the enigmatic starfish family Podosphaerasteridae (Asteroidea, Valvatida) with a morphological observation of the skeletal structure by micro-CT. Biodiversity Data Journal, 14, Article e194006. https://doi.org/10.3897/bdj.14.e194006

Image Credits: AI Generated

DOI: 10.3897/BDJ.14.e194006

Keywords: starfish, Podosphaeraster, mitochondrial genome, micro-CT, phylogenetics, convergent evolution, deep sea, Phylogenetic, position, enigmatic, family, Podosphaerasteridae

Hexapodid crabs are an odd bunch among brachyurans. Although they are true crabs in the family Hexapodidae, their name reflects the fact that the last pair of walking legs is reduced or absent, leaving them with only six visible ambulatory legs instead of the usual eight. They are small, delicate animals, often less than a centimetre across, and they typically live buried in soft sediments, sometimes in burrows shared with tube-dwelling worms. The Indo-West Pacific hexapodid fauna has been extensively revised in recent years, with 16 genera and 43 species currently recognised, but most of the recent taxa have been reported from the Pacific, with only a handful of records from the Indian Ocean.

Before this study, India could claim records for only two hexapodid genera with three species: Lambdophallus sexpes from the southwestern coast, Hexapus sexpes from the Bay of Bengal, and Hexapus bidentatus from the central-western coast. The new material, stored in the referral centre at the Centre for Marine Living Resources and Ecology in Kochi, doubles the generic diversity of the family in Indian waters overnight. The three new species are Mariaplax kochazhi, Mariaplax albucus, and Hexapinus clivus, each described and compared in detail with allied taxa from across the Indo-West Pacific.

Mariaplax kochazhi was collected off Kochi at a depth of 30 metres on a sandy bottom during cruise 343 in August 2015. The holotype is a male measuring just 5.5 by 3.5 millimetres, with paratypes including a female and a second male from the same grab sample. The species name honours its type locality, using the original Malayalam form Koch-azhi, meaning small sea. Kochi, historically known as the Queen of the Arabian Sea, now lends its name to a crab that is most similar to Mariaplax granulifera from Queensland, Australia, but can be distinguished by its proportionately wider carapace with larger granules on the dorsal surface, a pterygostomial region that is smooth with 5 to 7 striae, a rectangular ischium and more granulated merus of the third maxilliped, a subpentagonal male pleon telson, and a strongly curved S-shaped male first gonopod with a rounded distal tip.

The second new Mariaplax, M. albucus, was collected from the same station and cruise, with the holotype being a female of 6.2 by 3.5 millimetres. The species epithet derives from the Latin word albucus, meaning bulb of the lily, alluding to the bulging structure of the vulva that is diagnostic of the species. M. albucus is similar to M. sundaica, originally described from the Sunda Strait between Sumatra and Java, but can easily be differentiated by a carapace that is as wide as long rather than 1.7 times as long as wide, a pterygostomial region with 6 oblique striae, a relatively shorter and stouter fourth ambulatory leg merus that is 4.0 times wider than long, and the distinctive structure of the vulva. In M. albucus, the vulval operculum cover differs markedly from that of M. kochazhi, which is simple, rounded, and lacks a cover. Intriguingly, the male of M. albucus remains unknown, so the full suite of gonopod characters used to diagnose other species in the genus cannot yet be assessed for this species.

The third new species, Hexapinus clivus, was dredged from 433 metres off Tamil Nadu in the Bay of Bengal during cruise 392 in November 2019, with a juvenile female paratype recovered from trawl bycatch off the Shankarpur coast of West Bengal in March 2018. The name clivus is Latin for the sloping side of a mountain, referring to the gently sloping lateral margins of the fused first and second thoracic sternites, which form a subtriangular structure that is diagnostic of the species. H. clivus is morphologically close to the widely distributed H. simplex from the West Pacific, but it can easily be differentiated by weaker granulation on the carapace surface, a relatively shorter and stouter fourth ambulatory leg merus that is 2.5 times as long as wide, a proportionately wider male thoracic sternum with the fused sternites 1 and 2 being subtriangular with gently sloping lateral margins, and a semilunate vulva that is elevated and protruded, positioned adjacent to the suture between sternites 5 and 6.

The taxonomic detective work behind these descriptions relied on a battery of imaging and analytical techniques. Specimens were preserved in 5 percent formaldehyde before being transferred to 70 percent alcohol, photographed with a Leica S9i microscope, and illustrated using vector graphics in Adobe Illustrator. For scanning electron microscopy, specimens were cleaned manually with a soft brush in 70 percent alcohol, dehydrated in an ascending series of ethanol, and air-dried overnight in a desiccator before being mounted on silver stubs with carbon tabs. Micrographs were taken with an environmental SEM, a ZEISS EVO 15 with an extended-range cascade current detector set at 10 kilovolts. Notably, the specimens were not gold-coated, which is unusual for SEM work, allowing the material to be preserved in 90 percent alcohol and deposited in the museum after analysis rather than destroyed in the coating process.

The type specimens are deposited in the Bhavasagara Referral Centre, the national repository for reference collections of deep-sea fauna at CMLRE in Kochi, with comparative material retained in the Zoological Reference Collection of the Lee Kong Chian Natural History Museum at the National University of Singapore. The comparative material for H. clivus included specimens of H. simplex from Indonesia, Singapore, China, Hong Kong, and Japan, as well as photographs of the holotype of H. okinawa from Okinawa Island, described in 2025. The authors also flagged lingering uncertainty around Hexapus edwardsi, described from a single small subadult male from the Andaman Sea in 1976, noting that the male pleon as figured by Serène and Soh is unusual because somite 5 seems separate from fused somites 3 and 4, a condition atypical for the genus. Whether that figure is accurate will require re-examination of the specimen, and the authors concluded that H. clivus is clearly close to H. edwardsi but should be treated as a different species for the time being.

The discovery of three new species and two new generic records from Indian waters underscores how much of the region’s small-crustacean biodiversity remains undocumented, particularly in the poorly sampled soft sediments of the continental shelf and upper slope. The specimens came from routine grab and dredge sampling during fishery oceanographic surveys, suggesting that similar material may already sit unstudied in other reference collections across the Indo-West Pacific. With the genus Mariaplax now represented by 19 species and Hexapinus by eight, the Indian Ocean is beginning to catch up with the Pacific in hexapodid diversity, and the authors note that a tentative record of Hexapus granuliferus from the Andaman Sea by Serène and Soh in 1976 may actually belong to Mariaplax anfracta or even one of the new species described here, pending verification. For now, the sandy seabed off Kochi and the deep dredge sites off Tamil Nadu have yielded a reminder that even the most familiar coastlines can conceal crabs that science has never seen.

Subject of Research: Discovery of three new hexapodid crab species and first records of the genera Mariaplax and Hexapinus from Indian waters

Article Title: First records of the genera Mariaplax Rahayu & Ng, 2014 and Hexapinus Manning & Holthuis, 1981 from India, with descriptions of three new species ( Crustacea , Decapoda , Brachyura , Hexapodidae )

Article References: Prema, M., Cubelio, S. S., & Ng, P. K. L. (2026). First records of the genera Mariaplax Rahayu & Ng, 2014 and Hexapinus Manning & Holthuis, 1981 from India, with descriptions of three new species (Crustacea, Decapoda, Brachyura, Hexapodidae). ZooKeys, 1292, 349-372. https://doi.org/10.3897/zookeys.1292.204005

Image Credits: AI Generated

DOI: 10.3897/zookeys.1292.204005

Keywords: crabs, marine biology, taxonomy, new species, India, Arabian Sea, Bay of Bengal, hexapodidae, deep sea, biodiversity, First, records

The research, published in Frontiers in Ocean Sustainability, surveyed 126 Early Career Ocean Professionals, or ECOPs, drawn from 43 nationalities across six continents. The authors, based at the University of Edinburgh’s Ocean Voices Programme, partnered with the Deep-Ocean Stewardship Initiative, a network of deep-sea experts from more than 100 countries, to run an anonymised online questionnaire in four languages: English, French, Portuguese and Spanish. Their goal was to understand what prevents ECOPs from engaging in deep-sea policy and decision-making, and what support would help them overcome those barriers.

An ECOP is defined as a person who self-identifies as being early in their career, within 10 years or less of professional experience in any field related to the ocean. These professionals are increasingly recognized as key agents of change. They bring interdisciplinary training, fresh perspectives and modern methodologies to problems such as climate change, biodiversity loss and environmental justice. Because they are among the first generations of ocean scientists to routinely work across disciplinary boundaries, they are uniquely positioned to rethink, combine and apply knowledge regimes in the co-production of knowledge with decision-makers.

The survey results show that the appetite is there. Ninety percent of respondents expressed interest in participating in ocean policy and decision-making processes. When asked what role they could play, nearly 40 percent pointed to providing technical support for decision-making, 33 percent saw themselves participating directly in policy processes, and 23 percent highlighted contributing to policy briefs. Despite this enthusiasm, 84 percent of ECOPs reported perceiving challenges and barriers preventing their engagement—and the nature of those barriers split sharply along economic lines.

For ECOPs from developing countries, who made up 51 percent of participants, the most prominent barrier was a lack of financial resources. Not knowing who to approach came second. For ECOPs from developed countries, the picture was different: not knowing who to approach to engage in decision-making was the top-ranked barrier, followed by not knowing how they could contribute to policy processes. Concerns about confidence to communicate in a foreign language ranked lowest for both groups, suggesting that language, often assumed to be a major obstacle, is less decisive than money and access.

These findings matter because deep-sea research capacity is concentrated in developed nations. Exploration facilities, equipment and funding are mainly available in wealthy countries, which means ECOPs from developing countries are more likely to experience parachute science—research conducted in their own Exclusive Economic Zones without their meaningful involvement in planning, execution or publication. The survey suggests that without adequate funding, ECOPs risk being excluded from transdisciplinary research that addresses local needs, perpetuating inequalities that already shape the field.

When asked what opportunities could enhance their participation, 83 percent of participants identified funding to cover costs of attendance at policy and decision-making processes as a key opportunity. Seventy-two percent wanted more information on how to engage in policy processes, 71 percent called for general information and training around such processes, and 67 percent highlighted the importance of connections with relevant national or international delegates. Answers between participants from developed and developing countries were generally similar, but funds and connections with delegates were more important among participants from developing states, while information and training were slightly more relevant for those from developed countries.

The study also examined the role of international networks, adopting the Deep-Ocean Stewardship Initiative as a case study. Nearly 37 percent of participants reported already being members of a deep-sea network, including COBRA, Challenger 150, the Deep Ocean Observing Strategy and the UN Ocean Decade nodes. Forty participants provided reflections on how network engagement had affected their careers, with answers mostly positive: networking and collaboration, training and career development, access to science-to-policy information through webinars, and dissemination of educational resources and career opportunities. Some reported co-authorships, joining projects, writing reports and policy briefs, and applying for research awards as direct results of network membership.

Regarding how ECOPs would like to be supported by a deep-sea science-to-policy network, most participants indicated training programs would be crucial. They also pointed to access to information about funding and job opportunities, financial support to attend policy processes, opportunities to exchange knowledge with senior professionals, interaction with other ECOPs, and access to mentoring and professional advice. The authors argue that establishing nurturing spaces where learning and exchange take place is an important step for furthering ECOP engagement in deep-sea decision-making and for achieving future-proofing solutions for the ocean.

The findings arrive at a moment when global ocean commitments, including the UN Decade of Ocean Science for Sustainable Development, are investing in efforts to include historically marginalized voices. The UN Ocean Decade established the ECOP Programme to empower young professionals through networking and capacity-sharing opportunities with each other and with global institutions. Yet the study notes that only a handful of initiatives consistently provide funding to sustain ECOP attendance at policy processes, and these are not generally targeted at deep-sea researchers. The authors recommend targeted training on international agreements and negotiations related to the deep sea, such as the Biodiversity Beyond National Jurisdiction Agreement and the International Seabed Authority regulatory framework, alongside foundational courses in science advice and diplomacy. Mentorship, they argue, is fundamental: it provides mentees with access to valuable networks and a deep understanding of policy design, negotiation and implementation from experienced professionals. Without such support, the study warns, the next generation of ocean stewards may remain enthusiastic but locked out of the rooms where the future of the deep sea is decided.

Subject of Research: Ocean Sustainability

Article Title: Deep-sea early career ocean professionals (ECOPs) at the science-to-policy interface: needs, challenges, and opportunities against country economic status

Article References: Guilhon, M., Caldeira, M., & Lopes, V. (2026). Deep-sea early career ocean professionals (ECOPs) at the science-to-policy interface: needs, challenges, and opportunities against country economic status. Frontiers in Ocean Sustainability, 4, Article 1651081. https://doi.org/10.3389/focsu.2026.1651081

Image Credits: AI Generated

DOI: 10.3389/focsu.2026.1651081

Keywords: deep sea, early career ocean professionals, ocean governance, science policy interface, marine conservation, UN Ocean Decade, Deep-sea, early, career, ocean, professionals, ECOPs

The Crustacea collection at the Museum of Nature Hamburg is the largest of its kind in Germany and among the most significant in the world. It holds more than 850,000 specimens representing approximately 7,200 species, arranged across 2,100 genera and 350 families. Roughly 90 percent of the species are marine, with the Southern Ocean particularly well represented. The collection spans more than 70,000 catalogue numbers, and its taxonomic scope includes every class of crustacean except the obscure Cephalocarida. Amphipods dominate numerically with about 250,000 specimens, followed by marine isopods at roughly 170,000, while copepods and ostracods each contribute around a quarter of a million individuals. Decapods, the group that includes crabs and lobsters, account for about 37,000 specimens.

What makes the Cumacea type collection extraordinary is its deep connection to two towering figures in crustacean systematics: Carl Zimmer, who worked in the early twentieth century, and Ute Mühlenhardt-Siegel, whose career has been based in Hamburg. Most of Zimmer’s type material is deposited at the Museum für Naturkunde in Berlin, but a substantial portion of his Hamburg-related types remained in the city where the specimens were collected, largely during the Hamburger Magalhaensische Sammelreise of 1892 to 1893 and the Hamburger südwest-australische Forschungsreise of 1905, both led by the naturalist Johann Wilhelm Michaelsen. Archival evidence suggests that Zimmer received the material on loan rather than as a transfer of ownership. In his 1902 publication, he wrote that the Cumacea had been sent to him by the Hamburg Museum, implying that the specimens already belonged to Hamburg and that he was studying them on temporary loan.

Determining the correct type status of specimens more than a century old is no simple matter. Zimmer rarely designated a holotype in his original descriptions, leaving later researchers to infer the legal status of each specimen under the International Code of Zoological Nomenclature. Where Zimmer described a species from a single individual, the catalogue applies Article 73.1.2, which fixes that specimen as the holotype by monotypy. Where several specimens were listed, the entire series is treated as syntypes under Article 73.2. The researchers faced similar ambiguity with Mühlenhardt-Siegel’s more recent publications, in which she sometimes listed specimens simply as material without explicitly designating paratypes. In those cases, the team relied on catalogue books, index cards, and handwritten inner labels to establish each lot’s formal type status.

The geographic reach of the collection is staggering. More than 15 percent of the material was collected between 1883 and 1980, including specimens from historic expeditions such as the German S.M.S. Gazelle from 1874 to 1876, the British H.M.S. Challenger from 1876 to 1878, the Deutsche Tiefsee-Expedition of 1898 to 1899, and the Deutsche Südpolar-Expedition of 1901 to 1903. The bulk of the collection, however, was assembled after 1982, driven largely by a series of expeditions aboard the research vessel FS Polarstern under the German Polar Research Program. These voyages targeted the Drake Passage, the Scotia Sea, the Weddell Sea, continental Antarctica, the Strait of Magellan, Tierra del Fuego, and the Argentine and Brazil Basins, yielding thousands of hooded shrimp from the ocean floor.

More recent campaigns such as ANDEEP I through III and DIVA I through III enriched the collection with specimens from the South East Atlantic, particularly the Guinea, Angola, and Cape Basins. The North Atlantic and Arctic Oceans are also well represented through the BIOICE and IceAGE expedition series, while more limited holdings come from the equatorial Atlantic, including the Vema Fracture Zone and the Puerto Rico Trench. The Mediterranean and Red Seas feature prominently thanks to long-standing collaborations between researchers in Hamburg and Frankfurt, and smaller numbers of specimens originate from the Indian Ocean around the Maldives and the Pacific, including the Sea of Japan and the Kuril-Kamchatka Trench.

One of the most technically demanding aspects of the digitisation was data homogenisation. Historical expedition records were kept in multiple languages and formats, with some researchers relying on personal notes, others on station logbooks, and still others on cruise reports. The team created a unique collection event list for each expedition, selecting the most complete available dataset as the authoritative source. For historical voyages, the original Reisebericht, or travel report, was used, while modern campaigns on German research vessels such as FS Meteor and FS Sonne were linked to event lists published in the PANGEA data repository. Where the original species descriptions and the homogenised geographic data differ, the catalogue records both, with homogenised data prioritised in the digital collection database.

Selected type specimens were also photographed using a Keyence VHX-7000 digital microscope, producing high-resolution images that document morphological features critical for species identification. Each catalogue entry includes the original description reference, the currently accepted name, diagnostic characters, current geographic distribution, and detailed remarks on type status. The material citation format has been converted to a machine-readable standard, with interpretations and translations of the original German data presented in square brackets to preserve transparency. Several species carry evocative names reflecting their discovery in abyssal settings, such as Diastylis andeepae from the Weddell Sea at over 3,100 metres depth and Leucon pinocchio from the Argentine Basin, named for its unusually elongated pseudorostrum.

The significance of this work extends far beyond Hamburg. Type specimens are the permanent reference points against which all species identifications are made, and having a fully validated, publicly searchable digital record of them dramatically reduces the risk of taxonomic errors. Species described from single specimens, such as Eudorella splendida from South Georgia’s Moltke Harbour in 1883, or Bodotria quseirensis from a Red Sea reef flat, can now be traced directly to their physical holdings without requiring a visit to the museum. The catalogue also resolves long-standing confusions, such as the mistaken attribution of a Berlin specimen to Diastylopsis annulata when it actually belongs to the type series of a synonymised species.

The complete digitised collection is now openly accessible through the Leibniz Institute’s digital catalogue and through the Global Biodiversity Information Facility, with a companion data paper providing additional machine-readable detail. As the first instalment in a planned series covering the entire Crustacea type collection, this catalogue signals a broader shift in how natural history museums operate. Rather than functioning as static archives, collections are being transformed into dynamic research infrastructures where a scientist in Vladivostok, Paris, or Washington can examine the digital record of a hooded shrimp collected off Western Australia in 1905 before ever requesting the physical specimen. For biodiversity research in an era of accelerating ocean change, that accessibility may prove as important as the specimens themselves.

Subject of Research: Annotated type catalogue and digitisation of the Cumacea collection at the Museum of Nature Hamburg

Article Title: An annotated type catalogue and a fully digitised Crustacea collection of the Museum of Nature Hamburg, Zoology. Part I: Crustacea , Malacostraca , Peracarida , Cumacea

Article References: Mercado-Salas, N. F., Mühlenhardt-Siegel, U., Pereira, E., & Garilao, C. (2026). An annotated type catalogue and a fully digitised Crustacea collection of the Museum of Nature Hamburg, Zoology. Part I: Crustacea, Malacostraca, Peracarida, Cumacea. Evolutionary Systematics, 10(1), 137-193. https://doi.org/10.3897/evolsyst.10.187593

Image Credits: AI Generated

DOI: 10.3897/evolsyst.10.187593

Keywords: Cumacea, crustaceans, type specimens, museum collections, digitisation, biodiversity, taxonomy, Southern Ocean, deep sea, Museum of Nature Hamburg, Carl Zimmer, Ute Mühlenhardt-Siegel

The family Poecilopsettidae comprises just 21 valid species in three genera: two species in Marleyella, four in Nematops, and 15 in Poecilopsetta, the genus to which the new Japanese specimens belong. These fishes are characterized by a suite of anatomical features that set them apart from other flatfishes: eyes on the right side of the body, an ocular-side lateral line that curves upward above the pectoral fin, a blind-side lateral line that is reduced or absent entirely, a dorsal fin that originates above the upper eye, pectoral fins present on both sides of the body, no lachrymal bone on the blind side, and an autogenous first preural centrum and five hypurals in the caudal skeleton. Until now, Poecilopsetta colorata had been recorded only as far north as the South China Sea off Hong Kong, while Poecilopsetta praelonga had been known only from southern Taiwan at its northern limit. Both species had previously been documented from tropical and subtropical waters of the eastern Indian Ocean and western Pacific, from the Mozambique Channel and Arabian Sea in the west to the Philippines and northwestern Australia in the east, generally in depths of 216 to 732 meters.

Identifying deep-sea flatfishes is notoriously difficult, and the researchers behind the new report did not rely on a single character. Instead, they reassessed the diagnostic features of each species using a combination of fin-ray counts, scale counts, body proportions, skeletal details, and coloration. The two specimens of Poecilopsetta colorata, one from Tosa Bay measuring 103.1 millimeters in standard length and one from the Enshu-nada Sea measuring 91.0 millimeters, were identified by a specific combination of characters: dorsal-fin rays numbering 48 to 62, anal-fin rays 46 to 53, ocular-side pectoral-fin rays 9 to 12, and lateral-line scales 90 to 124. The body is deep, with its greatest depth at mid-body, and the eyes are separated by a flat, scaled interorbital area rather than being contiguous. Critically, the middle pectoral-fin rays on the ocular side are branched, a feature that distinguishes this species from close relatives in which all pectoral-fin rays are simple. A single large dark blotch on the ocular-side pectoral fin completes the identification.

The single specimen of Poecilopsetta praelonga, measuring 104.5 millimeters in standard length and collected from the same Enshu-nada Sea trawl station, presented a different anatomical profile. Its dorsal-fin rays number 57 to 65, anal-fin rays 45 to 55, ocular-side pectoral-fin rays 6 to 11, and lateral-line scales 91 to 111. The body is slender and oblong rather than deep and round, and the eyes are contiguous, touching each other rather than being separated by an interorbital space. All pectoral-fin rays are simple on both sides, with no branched rays, and the straight section of the lateral line is about three times the length of the lateral-line curve width. The pectoral fin is uniformly black, a striking feature that contrasts with the single large dark blotch of Poecilopsetta colorata. The researchers confirmed these identifications by comparing the Japanese specimens against type and non-type material held in collections in Japan and India, including the holotype of Poecilopsetta maculosa, a junior synonym of Poecilopsetta colorata, and the syntypes of Poecilopsetta praelonga from the Bay of Bengal off Colombo, Sri Lanka.

To bolster the morphological evidence, the team extracted total genomic DNA from muscle tissue preserved in 99.5 percent ethanol and amplified a partial mitochondrial cytochrome c oxidase subunit I gene, the standard DNA barcode for fishes. The polymerase chain reaction was run for 30 cycles with denaturation at 94 degrees Celsius for 15 seconds, annealing at 56 degrees Celsius for 15 seconds, and extension at 72 degrees Celsius for 30 seconds. The resulting sequences were registered in the International Nucleotide Sequence Database Collaboration under accession numbers LC924618, LC924620, and LC924619, providing a permanent molecular reference for the Japanese specimens. X-ray images were used to count unpaired-fin rays and vertebrae and to examine the caudal skeleton, following established terminology for flatfish osteology. All measurements were made to the nearest 0.1 millimeter with digital calipers and a divider, and the specimens are now deposited in the fish collections of Kochi University and the Kanagawa Prefectural Museum of Natural History.

Beyond the identification itself, the study produced a valuable reassessment of which characters are actually reliable for distinguishing species of Poecilopsetta. The presence or absence of branched ocular-side pectoral-fin rays has long been treated as species-specific, and the new evidence supports that view. The researchers examined 16 adult specimens of Poecilopsetta plinthus, a common Japanese species, and found that all had branched pectoral-fin rays, consistent with the species diagnosis. In contrast, the presence or absence of ocular-side transverse bands, long considered a species-level character, now appears less dependable. The Japanese specimen of Poecilopsetta praelonga had faint transverse bands on the ocular-side body, even though such bands have been considered absent in other adult specimens of the species previously examined. Similarly, the presence or absence of black blotches on the caudal fin, once treated as diagnostic, shows intraspecific variation in Poecilopsetta praelonga: some specimens have two pairs of dark blotches, others lack them entirely. The ocular-side head and body coloration of Poecilopsetta colorata also appears variable, with some adults showing many small black dots and others lacking them.

The most compelling explanation for how these tropical deep-sea flatfishes arrived in Japanese waters lies in the life history of the group and the physics of the western Pacific. Poecilopsettid species are thought to have a long pelagic larval stage, as evidenced by their large-sized pelagic larvae, which can reach roughly 26.5 to 29.0 millimeters in standard length in related species such as Poecilopsetta hawaiiensis. The Japanese specimens of Poecilopsetta colorata and Poecilopsetta praelonga retained faint black spots on the blind-side body, spots that are distinct in larval and juvenile Poecilopsetta but tend to disappear with growth and are lost in larger adults. This suggests the specimens had spent a relatively short time post-settlement before collection. Western Pacific localities where these species have been previously recorded, including the Philippines and Taiwan, sit squarely in the pathway of the Kuroshio Current, the strong western boundary current that flows northeastward past Taiwan and along the Pacific coast of Japan. The researchers therefore believe the larvae were transported northward by the Kuroshio during their pelagic stage and subsequently settled near their collection sites.

The Enshu-nada Sea records are the northernmost for both species, and the finding fits a broader pattern. Considerable range extensions probably driven by ocean-current dispersal have already been documented for the Atlantic species Poecilopsetta beanii, which has been recorded far outside its previously known distribution. The Kuroshio Current is well known to marine biologists as a dispersal mechanism for shallow-water tropical fishes that reach temperate Japan as larvae, contributing to the phenomenon of tropicalization in coastal Japanese waters. The new report extends that paradigm to deep-sea flatfishes, showing that the same current can carry larvae of deep-dwelling tropical species into temperate seas at bathyal depths. Because the specimens were collected by bottom trawl at 300 meters, a depth routinely worked by Japanese research and commercial vessels, it is plausible that other tropical deep-sea fishes are settling undetected in Japanese waters, waiting to be recognized by taxonomists with the right expertise.

The researchers proposed new standard Japanese names for both species: Gomafu-kawara-garei for Poecilopsetta colorata, referring to the black dots scattered on the ocular-side head and body of the reported specimens, and Hōba-kawara-garei for Poecilopsetta praelonga, referring to the body shape reminiscent of a leaf of the Japanese bigleaf magnolia. These names, based on the Enshu-nada Sea specimens, anchor the species in Japanese ichthyological tradition and will aid communication about the fishes among researchers, fishers, and conservationists. The study also highlights the importance of museum collections and comparative material: the identification of the Japanese specimens depended on access to type specimens collected more than a century ago in Sri Lankan waters, as well as modern comparative material from the Sulu Sea, the Indian Ocean off Java, and northwestern Australia. Without such collections, deep-sea biodiversity would remain largely invisible, and range extensions of the kind reported here would go unnoticed.

For deep-sea biologists, the Japanese records raise questions about whether these populations are self-sustaining or ephemeral, dependent on continued larval input from the south. The specimens were adults, as indicated by the lack of large round black spots on the ocular-side head and body, a feature characteristic of larvae and juveniles of Poecilopsetta colorata. Whether they can reproduce in Japanese waters, and whether their offspring would survive the cooler temperatures at the northern margin of the species ranges, remains unknown. What is clear is that the Kuroshio Current continues to reshape the biogeography of the western Pacific deep sea, one larva at a time, and that careful taxonomic work at trawl stations off Japan can catch these biogeographic shifts as they happen. The three specimens now preserved in Japanese museums are more than curiosities; they are evidence that the deep-sea fauna of temperate Asia is being actively replenished from the tropics by one of the ocean’s most powerful currents.

Subject of Research: The deep-sea flatfishes Poecilopsetta colorata and P. praelonga ( Actinopterygii , Pleuronectiformes , Poecilopsettidae ) from the Pacific coast of southern Japan

Article Title: The deep-sea flatfishes Poecilopsetta colorata and P. praelonga ( Actinopterygii , Pleuronectiformes , Poecilopsettidae ) from the Pacific coast of southern Japan

Article References: Obata, K., Mizumoto, Y., Kawai, T., & Wada, H. (2026). The deep-sea flatfishes Poecilopsetta colorata and P. praelonga (Actinopterygii, Pleuronectiformes, Poecilopsettidae) from the Pacific coast of southern Japan. Acta Ichthyologica et Piscatoria, 56, 299-314. https://doi.org/10.3897/aiep.56.197471

Image Credits: AI Generated

DOI: 10.3897/aiep.56.197471

Keywords: deep-sea, flatfishes, Poecilopsetta, colorata, praelonga, Actinopterygii, Pleuronectiformes, Poecilopsettidae, Pacific, coast, southern, Japan