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The Lower Triassic fossil record of brittle stars is relatively rich, yet most records published to date are based on poorly preserved or insufficiently known fossils. This hampers exhaustive morphological analyses, comparison with recent relatives or inclusion of Early Triassic ophiuroid taxa in phylogenetic estimates. Here, we describe a new ophiuroid from the Lower Triassic of Nevada, preserved as phosphatized skeletal parts and assigned to the new taxon Ophiosuperstes praeparvus gen. et sp. nov Maxwell, V. & Pruss. S.B. This unusual preservation of the fossils allowed for acid-extraction of an entire suite of dissociated skeletal parts, including lateral arm plates, ventral arm plates, vertebrae and various disk plates, thus unlocking sufficient morphological information to explore the phylogenetic position of the new taxon. Bayesian phylogenetic inference suggests a basalmost position of O. praeparvus within the Ophintegrida, sister to all other sampled members of that superorder. The existence of coeval but more derived ophiuroids suggests that O. praeparvus probably represents a member of a more ancient stem ophintegrid group persisting into the Early Triassic.

This Zenodo upload contains data from the draft genome of the brittle star Ophioderma brevispinum (Say, 1859). Please read our READ-ME.mdfile for additional details. You can citethe paper: Mashanov, V., Machado, D.J., Reid, R.et al.Twinkle twinkle brittle star: the draft genome ofOphioderma brevispinum(Echinodermata: Ophiuroidea) as a resource for regeneration research.BMC Genomics23, 574 (2022). https://doi.org/10.1186/s12864-022-08750-y. Abstract: Background—Echinoderms are established models in experimental and developmental biology, however genomic resources are still lacking for many species. Here, we present the draft genome ofOphioderma brevispinum, an emerging model organism in the field of regenerative biology. This new genomic resource provides a reference for experimental studies of regenerative mechanisms. Results—We report a de novo nuclear genome assembly for the brittle starO. brevispinumand annotation facilitated by the transcriptome assembly. The final assembly is 2.68 Gb in length and contains 146,703 predicted protein-coding gene models. We also report a mitochondrial genome for this species, which is 15,831 bp in length, and contains 13 protein-coding, 22 tRNAs, and 2 rRNAs genes, respectively. In addition, 29 genes of the Notch signaling pathway are identified to illustrate the practical utility of the assembly for studies of regeneration. Conclusions—The sequenced and annotated genome ofO. brevispinumpresented here provides the first such resource for an ophiuroid model species. Considering the remarkable regenerative capacity of this species, this genome will be an essential resource in future research efforts on molecular mechanisms regulating regeneration. &nbsp

Ophiuroidea is the largest class among extant echinoderms, with over 2000 described species assigned to 33 families. Here, the first identification key to the recently revised classification was developed, and revised morphological descriptions were derived from it, expanding the previous short diagnoses. The key was built by analyzing internal and external skeletal characters of predominantly the type species of each family, including at least two mutually exclusive attributes per family. Various numeric and multistate characters were used to create a traditional as well as an interactive key using the DELTA and Xper software programs­. Illustrations (SEM and digital photos) are included in the key to facilitate the assessment of character states by users. Not only is it the first identification key to the families, according to the recently proposed new classification and the examined species, but this interactive key also assists users in understanding the family level taxonomy of brittle stars. The interactive key allows new characters and states to be added, when more species will have been analyzed, without the need to reconfigure the complete key (as may be necessary with conventional keys).

International audience; The conspicuous Mediterranean brittle star Ophioderma longicauda (Bruzelius, 1805) has been discovered to represent a cryptic species complex, consisting of six nuclear clusters with contrasting reproductive modes (broadcast spawners and brooders). Here, O. longicauda is re-described. It is distinguished by a dark reddish-brown colouration both dorsally and on the ventral disc, and multiple tumid dorsal arm plates. One eastern Mediterranean brooding cluster is described as O. zibrowii sp. nov., characterized by a dark olive-green colour both dorsally and on the ventral disc, and single dorsal arm plates. Another brooder is described from Tunisia as O. hybrida sp. nov., with a highly variable morphology that reflects its origin by hybridization of O. longicauda and a brooder (possibly O. zibrowii sp. nov.), leaving the third brooding cluster as morphologically indistinguishable at this point and possibly conspecific with one of the others. The West-African O. guineense Greef, 1882 is resurrected as a valid species, differing morphologically from O. longicauda by predominantly single dorsal arm plates and light green or creamy white ventral side. Also from West Africa, O. africana sp. nov. is described, characterized by a dark brown colour, dorsally and ventrally, and single dorsal arm plates.

Identifiable remains of large deep-sea invertebrates are exceedingly rare in the fossil record. Thus, every new discovery adds to a better understanding of ancient deep-sea environments based on direct fossil evidence. Here we describe a collection of dissociated skeletal parts of ophiuroids (brittle stars) from the latest Pliocene to earliest Pleistocene of Sicily, Italy, preserved as microfossils in sediments deposited at shallow bathyal depths. The material belongs to a previously unknown species of ophiacanthid brittle star, Ophiacantha oceani sp. nov. On the basis of morphological comparison of skeletal microstructures, in particular spine articulations and vertebral articular structures of the lateral arm plates, we conclude that the new species shares closest ties with Ophiacantha stellata, a recent species living in the present-day Caribbean at bathyal depths. Since colonization of the deep Mediterranean following the Messinian crisis at the end of the Miocene was only possibly via the Gibraltar Sill, the presence of tropical western Atlantic clades in the Plio-Pleistocene of the Mediterranean suggests a major deep-sea faunal turnover yet to be explored.

Okanishi, Masanori, Kato, Moe, Watanabe, Hiromi Kayama, Chen, Chong, Fujita, Toshihiko (2020): Large populations of two new species of Ophiambix (Echinodermata, Ophiuroidea) discovered on Japanese hot vents and cold seeps. Raffles Bulletin of Zoology 68: 196-213, DOI: 10.26107/RBZ-2020-0017

Due to their peculiar and sometimes bizarre morphology, cave fauna (across invertebrates and vertebrates from both aquatic and terrestrial cave habitats) have fascinated researchers throughout history. Despite their success in colonizing most marine ecosystems, the adaptations of cave brittle stars (Ophiuroidea) to a stygobiotic lifestyle have been scarcely examined. Employing comparative methods on a data set of two species belonging to the genusOphionereis, this study addresses whether a cave-dwelling species from Cozumel exhibited similar troglomorphic traits as those of other taxa inhabiting caves. Our work demonstrated that some characters representing potential morphological cave adaptations inO. commutabiliswere: bigger sizes, elongation of arms and tube feet and the presence of traits potentially paedomorphic. In addition, an element of ophiuroid’s photoreceptor system, as well as pigmentation, was observed to be peculiar in this stygobiotic species, plausibly as a result of inhabiting a low light-energy environment. Finally, we add evidence to the statement thatO. commutabilisis a cave endemic species, already supported by demography, distribution and origin of this species, and now by a typical array of troglomorphisms.

Published records on the Ophiuroidea fauna of the Persian Gulf and Gulf of Oman are scattered in difficult to access journals and books. This study presents a compilation of all published records, complemented with data from new samples. Distribution, habitat and depth in the study area, as well as known Indian Ocean distributions, are included. The taxonomic status of all species was evaluated, critical comments were added as applicable, and several previous records were reassigned to other species. Ophiocoma erinaceus was removed from the fauna of the Persian Gulf and Gulf of Oman, because the only published record was instead Ophiocoma schoenleinii. Previous studies assumed that 46 species of brittle star were known from the study area, but only 38 species were confirmed by this re-assessment, including two new records (Ophiothrix (Ophiothrix) foveolata and Ophiocomella sexradia). Diagnostic features are supplied for difficult to distinguish species. Five species (Macrophiothrix elongata, Amphiura fasciata, Amphiura (Ophiopeltis) hexactis, Amphioplus echinulatus, and Amphioplus seminudus) are so far worldwide known only from the Persian Gulf area. A hexamerous, fissiparous species of Ophiothela that does not concur with any known species was found and may represent a new species. All newly collected species are illustrated with photographs.

The first morphological observation of a euryalid brittle star, Asteronyx loveni, using non-destructive X-ray micro-computed tomography (µCT) was performed. The body of euryalids is covered by thick skin, and it is very difficult to observe the ossicles without dissolving the skin. Computed tomography with micrometer resolution (approximately 4.5–15.4 µm) was used to construct 3D images of skeletal ossicles and soft tissues in the ophiuroid's body. Shape and positional arrangement of taxonomically important ossicles were clearly observed without any damage to the body. Detailed pathways inside the vertebral ossicles, lateral arm plates, and arm spines for passage of nerves and water vascular structures were observed. Inter-vertebral muscles were also observed. Forms and 3D arrangements of many important taxonomical characters of the euryalids were scrutinized by µCT in high enough resolution for taxonomic description of ophiuroids.

A revision of the genus Astrodendrum Döderlein (Ophiuroidea, Euryalida, Gorgonocephalidae) is based on 14 specimens, including the holotypes of Astrodendrum galapagense A. H. Clark and Astroconus capense Mortensen and a syntype of Gorgonocephalus sagaminus Döderlein. A new species Astrodendrum spinulosum is described from the Pacific coast of Japan. It is distinguished from its congeners in having conical external ossicles on aboral side of the disc; bulges on lateral edges of proximal arms; 1 terminal projection on each arm spine of proximal portion of the arm; 2 or 3 secondary teeth on each hook-shaped arm spine of distal portion of the arm. A taxonomic key to all six species of the genus Astrodendrum is provided.

Astrophiura caroleae, new species, is described from off Curacao in the southern Caribbean, and from the western Gulf of Mexico, in depths of 244 to 434 meters. This new species, the first in the genus Astrophiura to be described from the Atlantic Ocean, has a distinctive combination of characters, including regularly arranged primary plates, large radial shields whose radial edges are in contact for their entire visible length, and prominent tubercles on central and radial plates. The mottled reddish coloration of the dorsal surface of this species usually contrasts with the color of the substratum, rendering it readily visible in situ, despite its disc diameter of less than 10 mm. Like its congeners, A. caroleae is gonochoric, the gonads of females containing conspicuous masses of bright orange eggs that are approximately 165 µm in diameter. DNA Barcoding data are provided for this new species, these are the first for Astrophiura.

Two new species, Ophiolepis cavitata n. sp. and Ophiozonella cavernalis n. sp., are described from the specimens collected in shallow water submarine caves in the Ryukyu Islands, southwestern Japan. Ophiolepis cavitata n. sp. is distinguished from the other congeners in having prominent tubercle-shaped knobs on dorsal arm plates; two sizes of disc scales on the aboral disc, the larger surrounded by 3–8 times smaller disc scales; larger scales concave; radial shields wider than long; a trio of distinct scales present distal to each pair of radial shields; oral shields partly concave; 3 arm spines on proximal portion of the arms. Ophiozonella cavernalis n. sp. is distinguished from the other congeners in having polygonal, uniform size disc scales; oral shields almost as long as wide, shallow concave proximal sides that end in a fairly sharp point medially; arms about 9 times longer than disc diameter; 3 cylindrical arm spines, of which the oral most one is slightly larger than other 2 spines. Ophiozonella cavernalis n. sp. is the second finding of an anchialine-endemic ophiuroid and the first finding from the Pacific Ocean.

The reproduction of the brittle star Astrotoma agassizii was studied from deep waters of the South Atlantic Ocean, based on samples collected in August 2012, and May and September 2013. Ten samples from 800 to 1400 m depths off Mar del Plata Canyon were studied. The species was found to be a brooding simultaneous hermaphrodite. Hermaphroditic gonads contained testis and ovaries inside the same sacs. Both, ovary and testis contained different stages of gametogenesis development simultaneously. The largest oocyte recorded was 800 µm diameter. Gonads contained several stages of oocytes in different stages of gametogenesis. Free spermatozoa were observed in the lumen of the testis, together with spermatogenic columns. Five individuals, from a total of 30 examined, resulted brooding, and most contained mature ovotestis at the same time. Incubation occurs in five of the ten bursal sacs, containing 15 to 20 young juveniles each. Maximum disc diameter recorded for a brood was 1120 µm. Herein we hypothesize that Astrotoma agassizii could be continuous breeder species in the deep-sea. Fil: Berecoechea, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina Fil: Brogger, Martin Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina Fil: Penchaszadeh, Pablo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina

Neuropeptides are a diverse class of intercellular signalling molecules that mediate neuronal regulation of many physiological and behavioural processes. Recent advances in genome/transcriptome sequencing are enabling identification of neuropeptide precursor proteins in species from a growing variety of animal taxa, providing new insights into the evolution of neuropeptide signalling. Here, detailed analysis of transcriptome sequence data from three brittle star species, Ophionotus victoriae , Amphiura filiformis and Ophiopsila aranea , has enabled the first comprehensive identification of neuropeptide precursors in the class Ophiuroidea of the phylum Echinodermata. Representatives of over 30 bilaterian neuropeptide precursor families were identified, some of which occur as paralogues. Furthermore, homologues of endothelin/CCHamide, eclosion hormone, neuropeptide-F/Y and nucleobinin/nesfatin were discovered here in a deuterostome/echinoderm for the first time. The majority of ophiuroid neuropeptide precursors contain a single copy of a neuropeptide, but several precursors comprise multiple copies of identical or non-identical, but structurally related, neuropeptides. Here, we performed an unprecedented investigation of the evolution of neuropeptide copy number over a period of approximately 270 Myr by analysing sequence data from over 50 ophiuroid species, with reference to a robust phylogeny. Our analysis indicates that the composition of neuropeptide ‘cocktails’ is functionally important, but with plasticity over long evolutionary time scales.

Hypotheses on the age and possible antiquity of the modern deep-sea fauna put forward to date almost all agree on the assumption that the deep-sea fauna is largely the result of colonisation from shallow-water environments. Here, the fossil record of the Ophiacanthidae, a modern deep-sea brittle star family with extensive fossil occurrences at shelf depths, is systematically traced against a calibrated phylogeny. Several lines of evidence suggest that the Ophiacanthidae originated and greatly diversified in the deep sea, with most extant clades having diverged by the end of the Triassic at the latest. During the Jurassic, the family temporarily invaded shelf environments, attaining relative abundances and diversities comparable to those found in coeval and modern deep-sea settings, and gradually declined in abundance subsequently, to become largely restricted to the deep-sea again. The pattern of temporary expansion to shelf environments suggested here underpins the potential of deep-sea environments to contribute significantly to shallow-water biodiversity; an aspect that has mostly been neglected so far. It is speculated that the large-scale ophiacanthid invasion of shelf environments around the Triassic-Jurassic boundary was initiated by a change from thermohaline to halothermal circulation, attenuating the thermal stratification of the water column and thus providing opportunities for enhanced vertical migration of marine taxa.

The fossil record of Paleozoic ophiuroids includes a number of forms which share striking similarities with modern relatives in terms of skeletal morphology. These so called modern-type Paleozoic ophiuroids yield an enormous potential for a better understanding of ophiuroid evolution, yet the scarcity of accurate and sufficiently detailed morphological descriptions available to date precludes any further-reaching assessments. Here, we describe an articulated ophiuroid specimen from the Late Tournaisian (early Carboniferous) of Czatkowice quarry, southern Poland, as a new species Aganaster jagiellonicus sp. nov. The good preservation of the specimen allowed for a morphological analysis at a level comparable to recent ophiuroid descriptions. It shows remarkable morphological similarities with extant former ophiolepidids Ophiomusium and Ophiosphalma. The new find thus contributes to a solid basis for future investigations on the position of the modern-type Paleozoic ophiuroid in the phylogeny of the class.

Cryptic species are numerous in the marine environment. The brittle star Ophioderma longicauda is composed of six mitochondrial lineages, encompassing brooders, which form a monophyletic group, and broadcasters, from which the brooders are derived. To clarify the species limits within O. longicauda, we compared the reproductive status of the sympatric lineages L1 and L3 (defined after sequencing a portion of the mitochondrial gene COI) during the month of May in Greece. In addition, we genotyped a nuclear marker, intron i51. Each L3 female was brooding, whereas all L1 specimens displayed full gonads, suggesting temporal pre-zygotic isolation between brooders and broadcasters. Statistical differences were found among lineages in morphology and bathymetric distribution. Finally, the intron i51 was polymorphic in L1 (60 individuals), but monomorphic in L3 (109 individuals), confirming the absence of gene flow between brooders and broadcasters. In conclusion, the broadcasting lineage L1 and the brooding lineage L3 are different biological species., Les espèces cryptiques sont nombreuses dans l’environnement marin. L’ophiure Ophioderma longicauda est composée de six lignées mitochondriales, comprenant des incubants, qui forment un groupe monophylétique, et des individus à larves, desquels les incubants sont dérivés. Afin de clarifier les limites d’espèces chez O. longicauda, nous avons comparé l’état de reproduction des lignées sympatriques L1 et L3 (définies après séquençage d’une partie du gène mitochondrial COI) durant le mois de mai en Grèce. De plus, nous avons génotypé un marqueur nucléaire, l’intron i51. Chaque femelle L3 était incubante tandis que tous les individus L1 avaient les gonades pleines, suggérant un isolement pré-zygotique temporel entre les incubants et les individus à larves. Des différences statistiques de morphologie et de distribution bathymétrique ont été trouvées entre lignées. Finalement, l’intron i51 était polymorphe chez L1 (60 individus), mais monomorphe chez L3 (109 individus), confirmant l’absence de flux de gènes entre les incubants et dispersants. En conclusion, la lignée à larves L1 et la lignée incubante L3 sont des espèces biologiques différentes.

Background In metazoans, opsins are photosensitive proteins involved in both vision and non-visual photoreception. Echinoderms have no well-defined eyes but several opsin genes were found in the purple sea urchin (Strongylocentrotus purpuratus) genome. Molecular data are lacking for other echinoderm classes although many species are known to be light sensitive. Results In this study focused on the European brittle star Amphiura filiformis, we first highlighted a blue-green light sensitivity using a behavioural approach. We then identified 13 new putative opsin genes against eight bona fide opsin genes in the genome of S. purpuratus. Six opsins were included in the rhabdomeric opsin group (r-opsins). In addition, one putative ciliary opsin (c-opsin), showing high similarity with the c-opsin of S. purpuratus (Sp-opsin 1), one Go opsin similar to Sp-opsins 3.1 and 3.2, two basal-branch opsins similar to Sp-opsins 2 and 5, and two neuropsins similar to Sp-opsin 8, were identified. Finally, two sequences from one putative RGR opsin similar to Sp-opsin 7 were also detected. Adult arm transcriptome analysis pinpointed opsin mRNAs corresponding to one r-opsin, one neuropsin and the homologue of Sp-opsin 2. Opsin phylogeny was determined by maximum likelihood and Bayesian analyses. Using antibodies designed against c- and r-opsins from S. purpuratus, we detected putative photoreceptor cells mainly in spines and tube feet of A. filiformis, respectively. The r-opsin expression pattern is similar to the one reported in S. purpuratus with cells labelled at the tip and at the base of the tube feet. In addition, r-opsin positive cells were also identified in the radial nerve of the arm. C-opsins positive cells, expressed in pedicellariae, spines, tube feet and epidermis in S. purpuratus were observed at the level of the spine stroma in the brittle star. Conclusion Light perception in A. filiformis seems to be mediated by opsins (c- and r-) in, at least, spines, tube feet and in the radial nerve cord. Other non-visual opsin types could participate to the light perception process indicating a complex expression pattern of opsins in this infaunal brittle star. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-1035) contains supplementary material, which is available to authorized users.

This review presents a comprehensive overview of the current status regarding the global diversity of the echinoderm class Ophiuroidea, focussing on taxonomy and distribution patterns, with brief introduction to their anatomy, biology, phylogeny, and palaeontological history. A glossary of terms is provided. Species names and taxonomic decisions have been extracted from the literature and compiled in The World Ophiuroidea Database, part of the World Register of Marine Species (WoRMS). Ophiuroidea, with 2064 known species, are the largest class of Echinodermata. A table presents 16 families with numbers of genera and species. The largest are Amphiuridae (467), Ophiuridae (344 species) and Ophiacanthidae (319 species). A biogeographic analysis for all world oceans and all accepted species was performed, based on published distribution records. Approximately similar numbers of species were recorded from the shelf (n = 1313) and bathyal depth strata (1297). The Indo-Pacific region had the highest species richness overall (825 species) and at all depths. Adjacent regions were also relatively species rich, including the North Pacific (398), South Pacific (355) and Indian (316) due to the presence of many Indo-Pacific species that partially extended into these regions. A secondary region of enhanced species richness was found in the West Atlantic (335). Regions of relatively low species richness include the Arctic (73 species), East Atlantic (118), South America (124) and Antarctic (126). peerReviewed

Hemipholis cordifera is the correct name for the only known Western Atlantic species of Hemipholis. Hemipholis elongata, a name which has been used in place of H. cordifera, is a nomen dubium that cannot unambiguously be assigned to any known species of brittle star. Evidence is presented that the genus Hemipholis presently comprises only H. cordifera and its geminate Eastern Pacific congener Hemipholis gracilis, and it is shown that the latter name has priority over Hemipholis affinis. Hemipholis gracilis and H. cordifera are illustrated and compared to show how mature individuals can be distinguished. However, small individuals of both species are extremely similar. The latitudinal distributions of H. cordifera and H. gracilis appear to be causally related to coastal water temperature, possibly in conjunction with divergent ocean currents, and the relatively broad range of H. cordifera compared to H. gracilis is attributed to its cold tolerance and to the influence of widespread warm-water boundary currents in the central Western Atlantic. As regards the two other congeners that have been described, Hemipholis wallichii is revealed to be a juvenile ophiuroid incertae sedis, and Hemipholis microdiscus was previously transferred to the Amphiuridae and assigned the nomen novum, Amphiura microdiscoida.

Amphicutis stygobita is a new genus and new species of ophiuroid found in Bernier Cave, an anchialine cave on San Salvador Island, Bahamas. The species is small (disk diameter 3–4 mm) with short arms (2–2.5X disk diameter). Dorsal disk features include imbricated scales, and oval radial shields separated by a column of scales. Ventral disk features include imbricated scales, genital scales flat and thin, no bursal sacs, second tentacle pore of oral frame outside mouth slit, oral shields small ovals similar in appearance to disk scales, two to three oral papillae per jaw side with the proximal papillae usually in the infradental position, and ventral tooth at the apex of each jaw broadly rounded. The arms are the most distinctive feature. Dorsal arm plates are small diamond-oval shaped and separated from one another by a gap equal to the arm plate length. Ventral arm plates are small figure-8 shaped and separated from one another by a gap equal to the arm plate length. Lateral arm plates meet medially on dorsal and ventral sides and make up most of an arm segment. Each lateral arm plate bears two arm spines. Disk and arms are often formed by soft tissue outlining plates and scales, but lacking significant calcification. A raised skin persists after calcification, from which the genus name derives. The species is named for its aquatic cave-dwelling habit, apparently endemic to a single cave, and may be unique among ophiuroids in being restricted to a cave environment.