The new species was found during copepod sampling in Maholarn Cave, a famous tourist cave located within the grounds of a local temple in Nonghin District. The cave itself is ancient, estimated to be at least 265 million years old, and stretches about 220 meters in a single passage that is 3 to 4 meters wide and 6 to 7 meters high. Near the entrance, a small pool on the rock is filled by dripping water from a stalactite and dries out during the dry season from March to early May. Deeper inside, a large rimstone pool receives heavy flows of dripping water during the rainy season, and a small opening in the cave roof allows outside water to flow in. The cave floods from its far end up to the middle of its length, and mud covers the floor throughout the passage, creating a mosaic of microhabitats for its hidden fauna.

Sampling was carried out using a bottle with a mesh size of just 60 micrometers, fine enough to capture animals barely half a millimeter long, and the specimens were immediately fixed in 70 percent ethanol. Adult males and females were sorted under a stereomicroscope, then dissected in a glycerol and ethanol mixture and mounted on slides sealed with transparent nail polish for examination at 1,000 times magnification under a compound microscope. Selected specimens were dehydrated through a graded ethanol series, dried in a critical point dryer, mounted on stubs, coated with gold, and photographed with a scanning electron microscope. Pencil drawings made with a drawing tube attached to the microscope were finalized using graphic software, and the type specimens were deposited at the Thailand Natural History Museum in Pathum Thani and at the Faculty of Science of Nakhon Phanom University.

The holotype, an adult female, measures just 550 micrometers in body length excluding caudal setae, with a prosome-to-urosome ratio of 1.5. Her body is cyclopiform, widest at the cephalothorax, and ornamented with refractile points on the surface. The nauplius eye is indiscernible, a common trait among cave-dwelling species that live in perpetual darkness. The genital double-somite is enlarged laterally and slightly wider than long, bearing a pair of sclerotised semi-rounded structures and the reduced sixth legs dorsolaterally. The anal operculum is semicircular with a smooth free margin, a feature that immediately distinguishes the new species from its only congener. Each egg sac carries just two large eggs of about 70 micrometers in diameter, and the spermatophore is three-dimensional and C-shaped, another diagnostic difference from the L-shaped spermatophore of Siamcyclops cavernicolus.

The male, designated as the allotype, is slightly smaller at 540 micrometers and resembles the female in general segmentation and ornamentation except for the genital somite and antennules. His antennules are 15-segmented and geniculate, compared with the female’s 11-segmented appendages. The most striking male-specific feature lies on the third swimming leg, where the second endopodal segment carries a transformed apical spine bent inward with a rounded tip bent outward, serrated by two rows of spinules on its distal half, alongside an inner subterminal seta transformed into a strong, spine-like seta with a blunt tip. Such sexually transformed structures are important taxonomic characters in copepods, and their precise configuration helped the researchers confirm that the Maholarn Cave animals represent a species distinct from Siamcyclops cavernicolus, which was originally described from Ratchaburi and Prachuap Khiri Khan provinces in central Thailand.

The differential diagnosis rests on a suite of subtle but consistent differences. Beyond the smooth anal operculum, the new species has four elements on the second endopod of the first leg in females rather than five, six elements on the male third leg endopod rather than five, four setae on the second exopod of the fourth leg rather than five, and the distinctive C-shaped spermatophore. The species epithet isanus honors Isan, the local name for northeastern Thailand, and all known specimens were collected by the first author on 5 July 2013 from the rimstone pool in the innermost zone of the cave. The species is currently known only from its type locality, a pattern typical of many stygobiotic copepods with extremely restricted ranges.

The discovery carries broader significance because it required an emended diagnosis of the genus Siamcyclops itself. With only one species previously known, the genus was defined by the traits of Siamcyclops cavernicolus, including a well-developed anal operculum with a serrated free margin. The new species breaks that mold, showing that the genus encompasses variation in operculum shape, leg armature, and spermatophore form. The authors also compared Siamcyclops with its closest relatives, the genera Palaeocyclops, Thalamocyclops, and Bryocyclops, documenting morphological differences in mandibular palp structure, the size of exopodal versus endopodal segments on the swimming legs, spine and setal formulas, the shape of the fourth leg intercoxal sclerite, and the degree of reduction of the fifth leg.

That comparison revealed a fascinating evolutionary gradient. Scanning electron microscope photographs of the fifth leg show that in Siamcyclops the distal segment is reduced to a small lobe on the fifth pedigerous somite, while in Bryocyclops it is reduced even further, represented only by a small prominent knob. The researchers classified the fifth leg of the Bryocyclops group into three shapes based on the degree of reduction of the distal segment, with Thalamocyclops retaining the largest vestigial segment, Siamcyclops showing an intermediate small lobe, and Bryocyclops and Palaeocyclops showing the most extreme reduction. Interestingly, this means that among closely related genera, Siamcyclops actually shows the least reduced, more ancestral form in several characters, such as the mandibular palp bearing three setae, subequal exopodal and endopodal segments, and the presence of coxal setae on the second and third legs.

The authors caution that characters shaped by strong evolutionary selection should be used carefully in taxonomy because they may arise through parallel evolution or convergence. Subterranean cyclopine copepods share a suite of traits associated with life in semiterrestrial and underground habitats: tiny bodies usually less than 550 micrometers, short antennules of 10 or 11 segments, greatly reduced mandibular palps reduced to one to three setae, and reduced swimming legs with fewer, shorter, and stronger setae, sometimes transformed into spiniform structures that are advantageous in the confined spaces of the epikarst, the thin, water-filled zone of cracks and crevices at the boundary between soil and rock. The presence of a pseudosegment anterior to the genital double-somite in Siamcyclops and Bryocyclops, but not in the good-swimming Thalamocyclops, further reflects adaptation to cramped spaces.

Years of observation at Maholarn Cave add an ecological dimension to the taxonomic story. Bryocyclops maholarnensis, the first stygobiont ever recorded from northeastern Thailand, was collected only in the small pool near the cave entrance, while the new species was found in the large pool at multiple points in the inner section. Adults rather than juveniles are typically collected, suggesting these animals accidentally drop from the cave ceiling, especially during the rainy season, and live primarily in the epikarst above. With 14 stygobiotic and stygophilic copepods now recorded from caves in northeastern Thailand, including two calanoids, three cyclopoids, and nine harpacticoids, and roughly 6,000 caves across the country, about 90 percent of them in limestone, Thailand’s karst underworld continues to yield surprises. The genus Siamcyclops now appears endemic to the country, with its two species occupying well-separated ranges in the central and northeastern regions, a living reminder of how much remains undiscovered beneath the surface of Southeast Asia’s limestone landscapes.

Subject of Research: Taxonomic description of a new cave-dwelling cyclopoid copepod species from northeastern Thailand

Article Title:  Siamcyclops isanus sp. nov. ( Copepoda , Cyclopoida , Cyclopidae ), a new cave-dwelling species from northeastern Thailand

Article References: Watiroyram, S., & Koompoot, K. (2024). Siamcyclops isanus sp. nov. (Copepoda, Cyclopoida, Cyclopidae), a new cave-dwelling species from northeastern Thailand. Subterranean Biology, 49, 185-200. https://doi.org/10.3897/subtbiol.49.135303

Image Credits: AI Generated

DOI: 10.3897/subtbiol.49.135303

Keywords: copepoda, cyclopoida, new species, cave fauna, stygobiont, Thailand, limestone karst, taxonomy, epikarst, Subterranean Biology, Loei Province, crustaceans

DNA barcoding relies on a short, standardised stretch of the 5′ end of the mitochondrial Cytochrome c oxidase I gene, or COI, which acts as a molecular identifier unique to each species. The approach was proposed as a complement to traditional morphology-based taxonomy at a time when expert taxonomists are becoming scarce, cryptic species keep turning up under familiar names, and the identification of larval and juvenile stages remains notoriously difficult. Because the same gene region is sequenced across studies, researchers can pool homologous data into shared reference libraries such as GenBank and BOLD, which in turn underpin metabarcoding and environmental DNA surveys of biological communities.

Yet the reference libraries themselves are far from complete. When a sub-sample of major marine invertebrate groups was curated from BOLD around the 8th International Barcode of Life Conference in Trondheim in 2019, 39 percent of the reviewed species showed problems such as misidentification, ambiguity or shared barcodes. A gap analysis of the Iberian macroinvertebrate community found that roughly 63 percent of species lacked a DNA barcode altogether, with a substantial proportion flagged for significant intraspecific divergence and possible hidden diversity. Crustaceans, despite their ecological importance, are among the groups where robust genetic data are most lacking.

The genus Pachygrapsus illustrates these problems well. A 2005 revision recognised 12 species and suggested that P. propinquus should be treated as a junior synonym of P. minutus, but in March 2025 that name was reassigned by a WoRMS taxonomic editor to an entirely different species, Metopograpsus thukuhar. Meanwhile, P. socius had been recovered in 2005 for the Pacific representatives of what was then called P. transversus, on the basis of morphological and genetic differences. Today 13 species are accepted in WoRMS, distributed across tropical and temperate intertidal zones worldwide, but the genetic coverage of these species is anything but even.

To quantify the gaps, the team retrieved all COI 5′ region sequences available for the genus from GenBank and BOLD, amounting to 332 haplotypes across 10 species, and contributed eight new COI sequences of P. maurus collected by hand at low tide from two islands of the Azores Archipelago. The new sequences, obtained from pereopod muscle tissue using standard extraction, PCR with the jgLCO1490 and jgHCO2198 primers, and bi-directional Sanger sequencing, were deposited in GenBank under accession numbers PQ570873-76, with the representative specimens registered in BOLD under the bin AGP6456. The full dataset, including reconstructed original datasets from earlier studies of P. crassipes and P. marmoratus, comprised 1,032 sequences.

The analysis combined a Maximum Likelihood phylogenetic tree built in IQ-TREE 2 under the TN+F+I+G4 model, with four sequences of the outgroup species Grapsus adscensionis, and a statistical parsimony haplotype network generated with TCS at a 95 percent connection limit. Members of the same species formed monophyletic groups with high support values, and the network revealed distinct clusters corresponding to each species. Pairwise divergences were calculated as uncorrected p-distances and Kimura 2-parameter distances in MEGA11, with the barcoding gap assessed for each species as the difference between the minimum interspecific distance and the maximum intraspecific distance.

The headline result is a clear barcoding gap for every species with sufficient data, with average interspecific p-distances of 18.75 percent, exceeding the 17.16 percent previously reported for decapods. Average intraspecific variation, at 0.70 percent, also exceeds the previously described maxima for crustaceans, which hover around 0.38 to 0.48 percent. The authors suggest that this elevated within-species variation may reflect the current taxonomy of the genus overlooking cryptic species, and since K2P distances are known to inflate divergence, the fact that the p-distance values still surpass published figures strengthens confidence in both the gap and the hidden diversity.

Two biogeographic patterns stand out. Populations of P. gracilis from the east and west Atlantic show substantial divergence of 3.6 percent p-distance, with their haplotype networks completely separated at the 95 percent connection limit, suggesting very limited gene flow across the ocean and a possible case of ongoing speciation. Notably, one cluster corresponds to a Galician population thought to have been introduced by ship hull fouling from the Ivory Coast, consistent with earlier records of Pachygrapsus on vessels and an identical 16S match between Galician and Ivory Coast crabs. Similarly, P. crassipes populations from the east and west North Pacific, separated by six mutational steps between their closest haplotypes, echo earlier findings of restricted trans-Pacific gene flow and a proposal to recognise them as two different species.

The study also exposes stark inequities in genetic data availability. Three species, P. corrugatus, P. maurus and P. socius, lacked any information for the standard barcoding region, and in the case of P. socius the available COI sequences come from a different, downstream region of the gene that cannot be compared directly. P. loveridgei, known only from museum collections, has no genetic data at all. By contrast, P. crassipes and P. marmoratus dominate the literature and citizen-science records alike, together accounting for over 90 percent of genus observations on iNaturalist, a skew the authors attribute to abundance, commercial interest and geography in the Northern Hemisphere.

The authors caution that COI phylogenies reflect only maternal lineages and that the high mutation rate of mitochondrial DNA can compromise resolution of deeper relationships, particularly given evidence from earlier studies that Pachygrapsus may be polyphyletic within the family Grapsidae. They therefore call for a thorough taxonomic revision integrating morphological, genetic and ecological data, including multi-locus approaches with both mitochondrial and nuclear markers. Beyond resolving the genus, the findings reinforce the value of DNA barcodes for broad-scale metabarcoding assessments, and highlight the need for greater research effort on the less-studied species to build a truly comprehensive picture of marine biodiversity.

Subject of Research: DNA barcoding of Pachygrapsus shore crabs to assess barcoding gaps, cryptic diversity and taxonomic uncertainties in marine crustaceans

Article Title: Mind the gap: DNA barcoding on Pachygrapsus crabs

Article References: Alves, C., Baptista, L., Madeira, P., Vaz Álvaro, N., Santos, A., Meimberg, H., Ávila, S. P., & Curto, M. (2025). Mind the gap: DNA barcoding on Pachygrapsus crabs. Metabarcoding and Metagenomics, 9, Article e152554. https://doi.org/10.3897/mbmg.9.152554

Image Credits: AI Generated

DOI: 10.3897/mbmg.9.152554

Keywords: DNA barcoding, Pachygrapsus, COI gene, crustaceans, cryptic species, marine invertebrates, phylogeography, haplotype networks, taxonomic revision, metabarcoding, BOLD, GenBank

Camill Heller (1823–1917) was a prominent early zoologist who worked in Vienna, Innsbruck and Cracow. He published extensively on marine animals, including crustaceans, echinoderms, bryozoans and tunicates, and in later life turned to the alpine fauna. His greatest taxonomic legacy, in terms of newly described species, lies with the Decapoda, the order that contains shrimps, prawns, lobsters, crayfish and crabs. Heller published the majority of his carcinological contributions in the journal of the Vienna Zoological and Botanical Society, known from 1858 as the Kaiserlich-königliche zoologisch-botanische Gesellschaft, and later in various journals issued by the Mathematics and Natural Sciences Class of the Imperial Academy of Sciences in Vienna. In 2022, a team led by Sammy De Grave published a checklist, dates of publication and bibliography of the decapods described by Heller, a reference work intended to settle the identities and citation details of every name Heller ever coined. The new analysis reveals that some of those dates were adopted incorrectly because the authors misinterpreted the journals’ publication procedures.

The central error concerned the assumption that a paper physically presented at a scientific meeting had thereby been published. De Grave and colleagues noted that it was often clear a physical copy was presented at a meeting, and they adopted the session dates as the publication dates of the papers in question. The historical record shows this was not how the journals worked. Reading a paper at a session was part of the review process that preceded publication, not the moment of publication itself. Submitted papers at the Zoological and Botanical Society were presented at monthly meetings, their acceptance decided at sessions of an editorial committee, and the printed issues appeared quarterly. At the Academy, every paper intended for the printed publications was presented or at least announced in full or in excerpts at a class meeting, but the final printed version usually appeared in a subsequent issue one to six months after presentation. The meeting minutes, in other words, record when a paper was reviewed and accepted, not when it became available to the scientific community.

The consequences of this misreading were far from trivial. Heller published three crucial papers on Red Sea decapods, and in two of them he indicated the same species more than once as new. The checklist placed these papers in an incorrect order, which in turn affected which descriptions count as the original ones. The new paper provides historical notes on the two journals where Heller’s articles appeared and a complete list of his Decapoda publications with corrected dates of publication, together with a list of all new genus- and species-group names affected by the date changes. Among the names involved are currently valid genera such as Cryptochirus, Epixanthus, Hypocoelus, Pseudomicippe and Zozymodes, and dozens of species names including well-known Red Sea crabs and shrimps such as Atergatis anaglyptus, Alpheus charon, Hymenocera elegans and Clibanarius carnifex.

The mechanics of the Society’s journal are worth recounting because they explain the dating evidence. The journal, the Verhandlungen, had two sections with separate pagination: the Sitzungsberichte, detailing which presentations took place, books and separata presented, and general announcements relating to Society business, and the Abhandlungen, which constituted the scientific papers. Individual issues had no title page and appeared quarterly. In the Sitzungsberichte it was regularly announced which of the previous quarterly issues had been published. Copies of the issues could be picked up at meetings, and members living outside Vienna received the complete volume when it was finished unless they wished to receive the individual issues. Authors received twenty-five separates without their own title page and cover for free, and had the opportunity to order additional copies at their own cost that could be distributed in advance of the issues. These advance copies, known as preprints, are recognized under Article 21.8 of the International Code of Zoological Nomenclature as validly published, and the new paper uses this provision to anchor the dates of two of Heller’s earliest decapod papers.

Applying this framework, the study traces each of Heller’s papers through the minutes of both institutions. Heller’s two 1856 contributions on crustaceans from the Adriatic Sea were verbally presented at Society meetings on 1 October and 3 December 1856, but the quarterly issues in which they were to appear were delayed; the fourth issue of the 1856 volume was announced as published only at the session on 1 April 1857. Offprints of these two publications held in the library of the Crustacea Collection at the Natural History Museum in Vienna, each with its own pagination and the note that they come from the Society’s writings of 1856, can be considered valid preprints, and the publication date is adopted as 31 December 1856. Heller’s 1861 contribution on Red Sea crustaceans was recorded as presented orally on 5 December 1860 with the stipulation that it would appear in the next volume, and it appeared as the first paper in the first issue of the 1861 volume, announced at the meeting on 3 April 1861; the publication date is adopted as 31 March 1861.

The Academy papers follow a similar pattern, with the printed versions trailing the oral presentations by months. Heller’s paper on the crustacean fauna of the Red Sea, presented at the Academy’s meeting on 13 December 1860, appeared in the next volume of the Sitzungsberichte after the minutes of the meeting on 18 April 1861, in an issue due on 30 April whose receipt by the Society was mentioned at their meeting on 2 October 1861; it was therefore published after 30 April and before 2 October 1861. The continuation and conclusion of the same series was submitted by post, presented on 11 July 1861, and published following the minutes of the meeting on 18 July 1861 in an issue due on 31 July, with its receipt recorded on 4 December 1861. Heller’s paper on the macrourans, presented on 13 February 1862, was published after 31 March and before 2 July 1862, and his second report on crustaceans collected during the circumnavigation of the Austrian frigate Novara, presented on 2 April 1862, was published on or before 4 June 1862. His first part of the investigations on the littoral fauna of the Adriatic Sea, presented on 23 October 1862, appeared in a volume whose late issues were not available separately but in two bundles, with the receipt of the relevant bundle recorded on 1 April 1863.

The corrections resolve a nomenclatural puzzle that had previously required an extraordinary remedy. Under the checklist’s incorrect dates, Heller had described the same shrimp twice under two different names, Hippolyte trisetacea and Lysmata pusilla, and the earlier name under the wrong chronology would have been the later one. The 2022 work had therefore proposed designating Lysmata pusilla as a nomen oblitum, a forgotten name, and its junior synonym Hippolyte trisetacea as a nomen protectum, a protected name, a procedure reserved for cases where strict priority would destabilize well-established usage. With the correct publication dates, this chapter and its appendix become obsolete: Hippolyte trisetacea, published in 1861 in the first of the Red Sea papers, has priority over Lysmata pusilla, published later in 1861 in the third paper. The names now fall into their natural order without any need for exceptional conservation measures, and the nomenclatural stability that the nomen oblitum procedure was meant to protect is achieved by simple historical accuracy.

The study also corrects the record on which dates were already right. The publication dates for Heller’s papers from 1863, 1864, 1865, 1869, 1875 and 1876 had been adopted correctly by De Grave and colleagues, and the new notes leave them untouched. What the paper delivers instead is a complete list of Heller’s Decapoda publications with the correct dates of publication, and a list of the new genus- and species-group names established by Heller between 1856 and 1876 that are affected by the date changes, with currently valid names identified. For working taxonomists, the practical upshot is that citations of dozens of Heller’s Red Sea decapod names will need to shift from one Heller paper to another, and the chronological framework of his carcinological output is now anchored to the actual quarterly and monthly production schedules of two Viennese institutions rather than to the rhythm of their meeting calendars. The paper stands as a reminder that the dates on which scientific names depend are not abstractions but physical events, the moments when printed issues left the presses and reached the hands of readers, and that reconstructing those moments requires the kind of archival detective work that rarely attracts attention until the names it governs are at stake.

Subject of Research: Taxonomy

Article Title: Notes on some publication dates recently cited in the checklist of Decapoda described by Camill Heller

Article References: Dworschak, P. C. (2025). Notes on some publication dates recently cited in the checklist of Decapoda described by Camill Heller. Annals of the Natural History Museum Vienna, 126, 75-80. https://doi.org/10.3897/anhmw.168710

Image Credits: AI Generated

DOI: 10.3897/anhmw.168710

Keywords: taxonomy, crustaceans, Decapoda, nomenclature, zoological history, publication dates, Camill Heller, Red Sea, Notes, some, publication, dates

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 Coral Triangle, the vast marine region encompassing Indonesia, the Philippines, and surrounding waters, is famous for its reefs, but its smallest invertebrates remain largely unknown. Collecting and sorting these animals is painstaking, many species are extremely small and rare, and only a handful of taxonomists worldwide are familiar with the groups involved. The researchers warn that with near-shore habitats deteriorating under human pressure and global warming, species may vanish before their existence has ever been recorded. Their new descriptions are therefore not just an academic exercise but a fundamental basis for any future ecological study of these reefs, most of which in Northern Sulawesi are still in good condition.

The team gathered material during field trips to Bangka Island, partly with participants of Sam Ratulangi University. Using SCUBA diving and snorkelling, they collected coral rubble in buckets and brushed the epifauna of mangrove roots into small nets, all in shallow water between zero and five metres deep. After washing the samples and sieving the wash water through 0.2 millimetre meshes, specimens were sorted alive under a Zeiss stereomicroscope at the Coral Eye resort on Bangka Island and fixed in 80 percent ethanol. Among the small crustaceans, isopods proved much less abundant than tanaidaceans or amphipods, and only a few specimens of each anthurid species were found, underscoring how easily these animals escape notice.

The eight new species span several genera. Eisothistos minahasaensis, a unpigmented creature barely 2.1 millimetres long, was named after the Minahasa Peninsula and is distinguished by a characteristic tail fan with a precise arrangement of teeth and plumose setae. Two new Mesanthura species were also described: Mesanthura ratulangii, named for Samuel Jacob Ratulangi, a native of Northern Sulawesi who fought for Indonesian independence, and Mesanthura heliolatra, whose name derives from the Greek words for sun and worship, a nod to its preference for sunlit shallow water. The latter species shows remarkable sexual dimorphism, with males possessing atrophic mouthparts and an unusually modified first leg bearing a brush of hook-like setae.

Haliophasma annaclericiae, the first species of its genus found in Indonesia, honours Anna Clerici, who organizes the collection of plastic trash from beaches in North Sulawesi under the No Trash Triangle initiative. This isopod stands out with unusually large eyes, nearly half as long as its head, a strongly calcified cuticle with visible carbonate incrustations, and a long, spade-like telson with parallel lateral margins and a dorsal keel. Three further new species belong to the Apanthura group: Apanthuretta markuslasuti, named for Professor Markus Lasut of Sam Ratulangi University, Apanthuretta pinchans, whose name derives from the Latin word for to prick and whose first leg forms true pincers between propodus and dactylus, Amakusanthura mamuajae, named for marine ecologist Jane Mamuaja, and Apanthurella cuspidobtusa, the first representative of a newly erected genus.

Beyond the new species, the study resolves long-standing taxonomic tangles in the Haliophasma and Malacanthura groups. Species have been moved back and forth between these genera for decades, and the current assignment of species was inconsistent. The researchers identified reliable distinguishing characters: the maxilliped carries two palp articles in Haliophasma but three in Malacanthura, the mandibular molar process is absent or weak in Haliophasma but strong and well sclerotized in Malacanthura, and the telson of Haliophasma is generally linguiform with lateral flanges, often with a dorsal keel. Using these criteria, several species were reassigned, including Haliophasma hermani, H. pseudocarinata, and H. mombasa, which now belong to Malacanthura.

Perhaps the most striking discovery concerns a peculiar large hook on the first article of the first antenna, which arches over the cephalon in three species hitherto placed in Haliophasma and in the only species of the genus Nemanthura. This feature is unique within the entire suborder of Isopoda and provides a powerful argument for reinstating the old genus Exanthura Barnard, 1914 to accommodate all species with this hook. Haliophasma macrurum, originally described as Exanthura macrura in 1914 and later moved to Haliophasma, now returns to Exanthura as its type species. Nemanthura Wägele, 1981 is synonymized with Exanthura, and its type species Nemanthura valeriae is transferred accordingly. The revised genus now contains four species from South Africa, Western Australia, and off Venezuela.

The Apanthura group, comprising the genera Apanthura, Apanthuretta, Apanthuropsis, and Amakusanthura, contains 92 described species, some of which remain indistinguishable due to incomplete descriptions. The researchers found that many species show a mix of characters that do not fit available diagnoses. By comparing all published descriptions, they distinguished five groups sharing derived characters, proposed to be placed in different genera. A key character visible at first sight is the structure of the pleon, the posterior body region: Apanthura species have unfused pleonites in both sexes, Apanthuretta species show dorsal fusion of only pleonites four and five, Apanthuropsis species have a pleon wider than long, Amakusanthura species possess a pleon as long as wide or longer with narrow uropodal exopods, and the newly erected genus Apanthurella, diagnosed for the first time in this paper, combines dorsally fused pleonites with leaf-shaped uropodal exopods bearing a distodorsal sinuosity and a relatively short male first antenna.

The synonymy of Apanthuretta with Amakusanthura proposed by earlier authors is rejected. The type species of Amakusanthura, A. longiantennata, was described from a single sexually dimorphic blind male with all pleonites dorsally fused and a very long pleon, sharing no specific similarity with the type species of Apanthuretta. Moreover, all known males of species assigned to Apanthuretta that possess free anterior pleonites and fused pleonites four and five also show this character in maturity, a consistency that supports a monophyletic origin for the genus. The new classification allows more precise diagnoses of potentially monophyletic groups and makes the genera more coherent, though the authors caution that many species were described fragmentarily and that numerous redescriptions will be needed.

All type material is deposited in the Museum Zoologicum Bogoriense in Bogor, Indonesia, and in the Crustacea collection of the Leibniz Institute for the Analysis of Biodiversity Change in Hamburg, Germany. Specimens were collected under Indonesian research permit 275/SIP/IV/FR/4/2024 issued by BRIN, with a Letter of Agreement between Sam Ratulangi University and the German institute. The authors emphasize that DNA data for these species would be extremely useful for phylogenetic classification, but because the animals are rare and small, available material is usually just sufficient for morphological description and too valuable to be shredded. With advancing habitat deterioration in the Coral Triangle, the race is on to document these minute crustaceans before they disappear unnoticed.

Subject of Research: Taxonomy and biodiversity of marine isopod crustaceans in the Coral Triangle

Article Title: New Anthuroidea ( Crustacea , Isopoda ) from Northern Sulawesi (Indonesia) and a revised classification of the Haliophasma and Apanthura groups

Article References: Wägele, J. W., Undap, N. I. J., & Papu, A. (2026). New Anthuroidea (Crustacea, Isopoda) from Northern Sulawesi (Indonesia) and a revised classification of the Haliophasma and Apanthura groups. Evolutionary Systematics, 10(2), 409-467. https://doi.org/10.3897/evolsyst.10.204153

Image Credits: AI Generated

DOI: 10.3897/evolsyst.10.204153

Keywords: isopods, crustaceans, taxonomy, Coral Triangle, Indonesia, marine biology, biodiversity, new species, Evolutionary Systematics, Northern Sulawesi, Anthuroidea, Crustacea

The study, led by Mauricio Bonilla-Flores of the Institute of Geosystems and Bioindication at Technische Universität Braunschweig together with colleagues from Kiel, Jena, Aachen, and the Chinese Academy of Sciences, focused on the genus Heterocypris, one of the most diverse groups within the family Cyprididae with 72 known species. The team cultured three asexual species under identical laboratory conditions: Heterocypris exodonta from a temporary pond near Nam Co on the Tibetan Plateau at an altitude of 4728 meters, Heterocypris incongruens from a flowerpot in southern Mexico City, and Heterocypris salina from the Botanical Garden in Braunschweig, Germany. By raising all three under the same temperature range of 18 to 23 degrees Celsius and a fixed light cycle, the researchers could separate genuine species differences from environmental noise.

What emerged was a remarkably consistent developmental blueprint. All three species passed through nine distinct stages: eight juvenile instars and one adult stage, each separated by a molt in which the animal sheds its old shell and grows a new, larger one. The smallest juveniles, at stage A-8, measured only around 180 to 220 micrometers in valve length, barely visible to the naked eye. Adults, by contrast, reached over a millimeter in length. Heterocypris incongruens proved the largest of the three, with adult right valves averaging 1349 micrometers, while H. salina was the smallest at 1039 micrometers. These numbers may sound esoteric, but they form the reference library that paleontologists need to identify which species, and which life stages, are preserved in ancient sediments.

One of the most striking findings concerns the surface texture of the juvenile shells. Under scanning electron microscopy, the early instars of all three species displayed a pronounced polygonal reticulation, a net-like pattern of ridges covering the valve surface that included hexagonal and other irregular shapes. As the animals molted toward adulthood, this ornamentation progressively weakened and eventually disappeared entirely. This matters enormously for taxonomy: a fossilized juvenile shell with strong reticulation could easily be misidentified as a different species if researchers did not know that ornamentation fades with age. The study demonstrates that valve ornamentation alone is not a reliable taxonomic character, but becomes highly informative when evaluated in relation to developmental stage.

The eggs themselves proved equally revealing. All three species produce ellipsoidal eggs with a two-layered eggshell, an inner layer produced by the oocyte and an outer layer secreted by the ovarian epithelium, a structure first described in classical histological studies over a century ago. Yet the eggs differed dramatically in size between species even under identical laboratory conditions: H. incongruens eggs averaged 147 micrometers in diameter, H. exodonta eggs 129 micrometers, and H. salina eggs just 91 micrometers. Since all three were raised in the same water, at the same temperature, and fed the same spinach, these differences must reflect intrinsic species-specific traits rather than environmental influences, making egg size a potentially powerful diagnostic character.

The survival machinery packed into these eggs is extraordinary. Resting eggs of Heterocypris are known to withstand desiccation and extreme temperatures ranging from minus 18 to 42 degrees Celsius, and can remain viable in a dormant state for more than 20 years. In the study, eggs of H. exodonta were deliberately dried for 120 hours, causing them to collapse, yet after rehydration they turned orange within 20 minutes and regained their original diameter within an hour. This resilience underpins the formation of so-called egg banks, accumulations of viable dormant eggs in sediment that hatch when conditions turn favorable, acting as ecological reservoirs that allow populations to persist in ephemeral ponds that dry out seasonally and recolonize after disturbance.

The research also tested a venerable rule of crustacean biology. Brooks’ rule, proposed in 1886, holds that arthropods roughly double their volume with each molt, which translates into a linear size increase of about 1.26 per stage. The measured growth ratios in all three Heterocypris species converged on values close to this prediction, ranging from about 1.21 to 1.26 for valve length and height. But the averages concealed considerable variation among species and stages, with larger increments in intermediate instars and smaller ones in the final molts, possibly linked to the development of reproductive structures at maturity. The authors conclude that geometric growth represents a general tendency rather than a fixed rule, and that growth ratios alone cannot reliably distinguish closely related species.

Raising the animals was not without its challenges. The researchers found that newly hatched A-8 juveniles kept in isolation died within 7 to 9 days despite being fed, but when 10 to 15 juveniles shared a compartment, survival extended to 25 to 30 days and many reached adulthood. This aggregation behavior, likely tied to favorable water conditions and food access, also appeared to protect against fungal contamination. The complete life cycle from hatching to final molt took only about 35 to 60 days under laboratory conditions, though the team noted that development slows dramatically in winter, with juveniles apparently entering a dormant phase until warmed by sunlight.

The broader implications reach deep into paleoclimate science. Because ostracod valves are often the only part of the animal preserved in sediments, and because early juvenile stages calcify weakly and preserve poorly, sediment records are inherently biased toward adults and later instars. Understanding the full ontogenetic sequence allows researchers to distinguish genuine population structure from the effects of sediment transport, wind-driven hydrodynamics, and taphonomic loss. It also helps resolve a longstanding puzzle: whether widespread species like H. incongruens and H. salina are truly cosmopolitan or actually complexes of cryptic taxa, a question that molecular studies suggest is increasingly likely, with multiple clonal lineages already documented within these morphologically uniform animals.

Ultimately, the study delivers something the field has lacked for over a century: complete, high-resolution documentation of every developmental stage in three Heterocypris species, from the layered architecture of the eggshell to the fading reticulation of the growing valve. As lake sediments worldwide are interrogated for clues about monsoon dynamics, drought history, and ecosystem response to warming, these tiny crustaceans and their meticulously catalogued life stages will serve as indispensable benchmarks, ensuring that the stories locked in ancient mud are read with the precision they deserve.

Subject of Research: Ontogenetic development, egg morphology, and valve growth of three cultured freshwater ostracod species of the genus Heterocypris

Article Title: Ontogenetic growth of three cultured species of Heterocypris Claus, 1892 (Crustacea: Ostracoda): eggs and valve morphology

Article References: Bonilla-Flores, M., Pérez, L., Frenzel, P., Echeverría-Galindo, P., Wang, J., & Schwalb, A. (2026). Ontogenetic growth of three cultured species of Heterocypris Claus, 1892 (Crustacea: Ostracoda): eggs and valve morphology. Journal of Micropalaeontology, 45(1), 429-453. https://doi.org/10.5194/jm-45-429-2026

Image Credits: AI Generated

DOI: 10.5194/jm-45-429-2026

Keywords: ostracods, Heterocypris, ontogeny, valve morphology, egg banks, Brooks' rule, paleoecology, Tibetan Plateau, laboratory culture, scanning electron microscopy, crustaceans, lake sediments

The review traces the full journey of these contaminants from source to sediment. Microplastics and nanoplastics originate from single-use packaging, synthetic textiles, fishing gear, industrial waste and the slow fragmentation of larger debris. They reach rivers, lakes and coastal seas through urban runoff, wastewater effluents and even atmospheric deposition, and because many particles are denser than water or become fouled by microbial biofilms, they ultimately settle into sediments. That is precisely where benthic crustaceans live and feed. By sifting through contaminated mud, grazing on biofilms and consuming prey that have already ingested plastic, animals such as crayfish, fiddler crabs, shrimp and horseshoe crabs encounter plastic at concentrations far higher than those measured in the open water column. Their wide distribution across marine, brackish and freshwater habitats, combined with their central position in aquatic food webs, makes them ideal bioindicators of plastic pollution.

Once in contact with a crustacean, plastic particles find multiple routes inside the body. The review confirms uptake through ingestion, through the filtration surfaces of the gills, and through direct dermal contact, which is particularly significant during molting, when the old exoskeleton is shed and the new cuticle is still soft and permeable. From these entry points, particles are biodistributed to the hepatopancreas, the gut, the gills and the hemolymph, the crustacean equivalent of blood. Studies cited in the review have detected microplastics in the edible muscle tissues of commercially important species such as the Pacific whiteleg shrimp Litopenaeus vannamei and the giant river prawn Macrobrachium rosenbergii, raising questions that extend beyond ecology into food safety. In red swamp crayfish, researchers have even documented bio-mediated fragmentation, in which digestive processing breaks larger microplastics into smaller fragments that may penetrate tissues more deeply.

What happens next follows a disturbingly consistent sequence that the authors describe as a progression from physical interference to cellular damage to whole-organism dysfunction. At the coarsest level, particles can obstruct the digestive tract or physically dilute the nutritional value of food. At the cellular level, the dominant mechanism is oxidative stress: plastic particles trigger the overproduction of reactive oxygen species, overwhelming antioxidant defenses and damaging lipids, proteins and DNA. Histopathological lesions in the hepatopancreas, gut and gills have been documented repeatedly across species, from polyethylene-exposed whiteleg shrimp to polystyrene-exposed crayfish. Genotoxic effects, including DNA strand breaks and altered expression of apoptosis-related genes in the hepatopancreas of juvenile prawns, indicate that the damage reaches the genome itself.

Beyond individual cells, the review catalogs a cascade of physiological disruptions. Immune suppression emerges as a recurring theme, with hemocytes, the circulating immune cells of crustaceans, showing impaired function after plastic exposure, and lysozyme and other immune-related genes being downregulated in shrimp fed contaminated feed. The gut microbiome, increasingly recognized as a pillar of crustacean health, falls into dysbiosis: studies on crayfish, brine shrimp and Chinese mitten crabs all report shifts in intestinal microbial communities following microplastic or nanoplastic exposure, some of which persist even after the animals are returned to clean water. Endocrine disruption adds another layer of complexity. Plasticizers such as phthalates and bisphenols leach from particles and interfere with hormone signaling, and nanoplastic exposure has been shown to disturb sex hormones, alter vitellogenin levels and impair gonadal development in shrimp and crayfish.

Osmoregulation, the delicate ionic balancing act that allows crustaceans to thrive in waters of varying salinity, is also compromised. Proteomic analyses of nanoplastic-exposed whiteleg shrimp gills reveal disturbances in ion transport proteins, and experiments with fiddler crabs show that salinity modulates both microplastic accumulation and osmoregulatory toxicity. Metabolism suffers in parallel: lipid metabolism is altered in the hepatopancreas of redclaw crayfish, energy metabolism shifts in the oriental river prawn, and growth rates decline in species from brine shrimp to horseshoe crabs. Perhaps most striking for an animal group defined by its armor, molting itself is disrupted. Polystyrene nanoplastics reduce molting frequency in adult Macrobrachium nipponense, polyethylene terephthalate microfibers alter molting patterns in whiteleg shrimp, and microplastics weaken the mechanical properties of the exoskeleton, leaving animals structurally and developmentally vulnerable.

The consequences ripple outward into behavior and reproduction. Hermit crabs exposed to microplastics show impaired cognition and disrupted contest behavior, undermining the shell-selection decisions that determine their survival. Whiteleg shrimp exposed to microplastics display impaired appetite, olfaction and digestion, eroding the sensory and motivational machinery of feeding. Reproductive disorders complete the picture: polystyrene microplastics induce male reproductive toxicity and transgenerational effects in freshwater prawns, microplastics combined with the hormone-mimic bisphenol A hamper gonadal development in whiteleg shrimp, and microplastic fibers reduce reproduction in Pacific mole crabs at environmentally relevant concentrations. For populations, these sublethal effects matter more than acute lethality, because they erode fitness quietly across generations.

One of the review’s most consequential arguments concerns co-exposure. In the real world, crustaceans never encounter plastics alone. The particles act as vectors for heavy metals, pesticides, pharmaceuticals and other pollutants, adsorbing these chemicals onto their surfaces and enhancing their bioavailability. Experiments show that polystyrene microplastics increase lead bioaccumulation and health damage in the Chinese mitten crab, that microplastics enhance copper-induced immunotoxicity in red swamp crayfish, and that combined exposure to nanoplastics and metals or antibiotics produces oxidative stress and gut damage in juvenile horseshoe crabs exceeding what either stressor causes alone. Environmental variables amplify the problem further: warming increases microplastic accumulation and physiological toxicity in fiddler crabs, temperature modulates the physiological response of crayfish to polyethylene, and climate change is expected to alter the behavior, distribution and risk profile of freshwater microplastics overall.

The review also confronts the question of trophic transfer, the movement of plastics up food chains. Nanoplastics have been shown to pass from brine shrimp to fish, from microalgae through crustaceans to small yellow croakers, and from American horseshoe crab eggs to shorebirds, demonstrating that crustaceans can serve as both recipients and conduits of plastic contamination. Accumulation kinetics studies in water fleas and mysids confirm that transfer between trophic levels is measurable and biologically meaningful. Yet the authors identify significant gaps that still block a complete risk picture: methodologies for sampling, identifying and quantifying microplastics remain poorly standardized, long-term monitoring data are scarce, and trophic transfer in freshwater and aquaculture settings is especially under-studied, even though shrimp ponds and crayfish farms are demonstrably contaminated.

The authors’ conclusion is a call for integrated risk assessment frameworks that account simultaneously for particle characteristics such as size, polymer type and shape, for environmental variables such as temperature and salinity, and for multi-stressor interactions that dominate real ecosystems. Encouragingly, some mitigation avenues are emerging, including evidence that biofloc microorganisms can enhance shrimp resistance to microplastics and that Spirulina supplementation can remediate some intestinal damage in exposed crayfish. But the central message stands: crustaceans, from the smallest copepod to the largest crab, are integrating the entire toxicological spectrum of plastic pollution in their tissues, their genes and their behavior. Reading them carefully, the review argues, is one of the best ways humanity has of understanding what the plastic age is doing to aquatic ecosystems, and of acting before projected emissions quadruple the burden.

Subject of Research: Toxicological effects of microplastics and nanoplastics on crustaceans

Article Title: Integrated toxicological approach to microplastics and nanoplastics in crustaceans

Article References: Banaee, M., Shakeri, R., Günal, A. Ç., Yüce, P. A., Trivedi, A., & Faggio, C. (2026). Integrated toxicological approach to microplastics and nanoplastics in crustaceans. Ecotoxicology, 35(8), Article 175. https://doi.org/10.1007/s10646-026-03155-z

Image Credits: AI Generated

DOI: 10.1007/s10646-026-03155-z

Keywords: microplastics, nanoplastics, crustaceans, ecotoxicology, oxidative stress, bioaccumulation, endocrine disruption, gut microbiome, trophic transfer, multi-stressor toxicity, aquatic pollution, bioindicators