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

Squat lobsters are not lobsters in the culinary sense. They are decapod crustaceans of the infraorder Anomura, the same group that includes hermit crabs and king crabs, and most species are small, laterally compressed animals that shelter in crevices or perch on hard substrates, waving their elongated claws in the current to feed. The family Munidopsidae, to which the new species belongs, is dominated by deep-water lineages, many of which are associated with seamounts, canyons, and other hard-bottom habitats far below the reach of sunlight-driven photosynthesis. Because these environments are geographically isolated from continental shelves and exhibit complex topographic and oceanographic patterns, they often harbor distinctive benthic communities, including endemic species found nowhere else.

The specimens that led to the new species were collected in late March 2024, during FORV Sagar Sampada cruise 404, using a chain bag dredge deployed at a station located at 8.54 degrees North, 73.26 degrees East, on what the team designated seamount 4 off Minicoy. Four individuals were recovered: an ovigerous female designated as the holotype, one male and two females designated as paratypes. All four came from the same dredge haul at 360 meters depth, collected by R. Ravinesh and his shipboard colleagues. The animals are small even by squat lobster standards, with postorbital carapace lengths ranging from about 4.5 to 5.2 millimeters and carapace widths between 3.7 and 4.4 millimeters.

Back in the laboratory, the team cleaned, photographed, and examined the specimens under a Leica M80 stereo-zoom microscope fitted with a high-definition camera, taking measurements with calibrated imaging software. The morphological analysis followed the descriptive terminology established in a 2019 revision of the genus by Rodríguez-Flores, Macpherson, and Machordom, which had itself described fifteen new species and remains the taxonomic backbone for Leiogalathea. Every appendage was scrutinized: the spination of the third maxillipeds, the proportions of the first pereopods, the armature of the walking legs, the shape of the rostrum, and the pattern of ridges sculpting the carapace, the armored plate that covers the head and thorax.

That ridge pattern proved decisive. Leiogalathea samudragiri shares with three of its closest relatives, L. achates, L. evander, and L. laevirostris, an unarmed hepatic margin on the carapace, a feature that initially groups them together. But the new species stands apart in two consistent characters: its mesogastric and mid-transverse ridges on the carapace are uninterrupted, running continuously across the midline, and the posterior half of the carapace bears six transverse ridges. In the three related species, the mid-transverse ridge is interrupted medially or submedially, and only four or five ridges follow it. Additional differences reinforce the split. Unlike L. achates, the new species lacks a spine on the posterior branchial margin and has subequal rather than unequal distal spines on the second antennal article. Unlike L. evander, it carries three well-developed rostral teeth rather than four to six rudimentary ones, and its abdominal tergite 3 bears a single elevated ridge rather than two. Unlike L. laevirostris, the basal antennular article is unarmed at its distomesial corner, and the mesial margin of the first pereopod’s carpus carries one spine rather than three.

The detailed anatomy is a study in miniature engineering. The rostrum, the pointed projection between the eyes, is slightly downturned and flattened dorsally, about 1.5 times as long as broad, with serrated lateral margins bearing three small teeth and three progressively smaller rudimentary teeth. The first pereopods, the elongated claws that give squat lobsters their characteristic silhouette, extend to nearly three times the carapace length and are clothed in uniramous stiff setae, with the merus segment alone slightly exceeding the carapace length and bristling with strong spines arranged along its mesial, dorsal, lateral, and ventral surfaces. The walking legs are moderately slender and laterally compressed, with propodi more than five times as long as broad and dactyli armed with rows of small, proximally diminishing teeth, each tipped with a slender movable spinule. The third maxilliped’s ischium terminates in a strong spine on its flexor margin and carries a crista dentata of twenty-two corneous denticles.

Even the coloration, recorded from freshly collected material, is distinctive and unexpectedly vivid for an animal living in near darkness. The rostrum and the anterior two-thirds of the carapace are bright orange, with light yellow patches on the posterior gastric region; the posterior carapace and anterior abdominal segments are pale orange, and the pereopods are bright orange marked with white patches. The species name itself is a nod to its habitat, combining the Sanskrit words samudra, meaning ocean, and giri, meaning mountain, a direct reference to the seamount where the animals were found. The holotype female was ovigerous, carrying eggs, which suggests the population was reproductively active at the time of collection.

The broader context makes the find more significant than a single addition to a checklist. The genus Leiogathea, established by Keiji Baba in 1969, is dominated by the Pacific Ocean, which hosts fourteen of its species, while the Atlantic and Indian Oceans had only two each before this description. The munidopsid fauna of the Northern Indian Ocean, the authors note, remains relatively unexplored compared with neighboring regions. A previous expedition had already yielded an unresolved Leiogalathea specimen from the Andaman Sea, reported as Leiogalathea sp. because it was damaged, hinting that the region harbors more diversity than the formal record reflects. The authors also point out that overlapping morphological characters among congeners probably indicate the existence of pseudocryptic species within the genus, externally near-identical lineages that only careful comparison of fine structural details, or genetic analysis, can separate.

The expedition itself is part of a larger national effort. The samples were gathered under India’s Deep Ocean Mission, specifically the Samudrayaan program, coordinated through the Ministry of Earth Sciences, with CMLRE in Kochi leading the faunal exploration aboard the research vessel Sagar Sampada. Seamounts have been recognized as ecological hotspots since faunal explorations began in the 1940s, yet only a handful of Indian Ocean seamounts have ever been surveyed, leaving vast tracts of undersea topography biologically uncharted. Voucher specimens of the new species, registered under the catalog numbers IO/SS/ANO/00195 through 00197, are deposited in the Bhavasagara Referral Centre at CMLRE, which serves as the regional node of the Ocean Biodiversity Information System for the Indian Ocean, and the associated occurrence data will be made publicly available through the OBIS portal.

For now, Leiogalathea samudragiri is known only from its type locality in the Lakshadweep Sea off Kerala, at 360 meters depth, a single seamount station in an ocean basin where deep-water sampling effort remains sparse. Whether the species is a narrow endemic restricted to one undersea mountain, as many seamount-associated invertebrates appear to be, or simply under-collected across a wider range, will only be resolved by further expeditions. What the discovery does demonstrate is that even a single dredge haul, examined with the right taxonomic expertise, can reveal a lineage new to science in one of the most heavily trafficked yet least explored marine regions on Earth, and that the census of life on the Indian Ocean’s seamounts has barely begun.

Subject of Research: Taxonomic description of a new deep-sea squat lobster species from an Arabian Sea seamount

Article Title: A new deep-sea munidopsid squat lobster of the genus Leiogalathea Baba, 1969 (Decapoda: Anomura) from the southeastern Arabian Sea, India

Article References: Tiwari, S., Padate, V. P., & Cubelio, S. S. (2026). A new deep-sea munidopsid squat lobster of the genus Leiogalathea Baba, 1969 (Decapoda: Anomura) from the southeastern Arabian Sea, India. Discover Oceans, 3(1), Article 6. https://doi.org/10.1007/s44289-026-00117-5

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00117-5

Keywords: squat lobster, Leiogalathea samudragiri, seamount, Arabian Sea, deep sea, taxonomy, new species, Munidopsidae, Decapoda, Anomura, Deep Ocean Mission, marine biodiversity