Showing posts with label Ichthyology. Show all posts
Showing posts with label Ichthyology. Show all posts

Thursday, 24 July 2025

Rypticus africanus: A new species of Soapfish from the eastern Atlantic.

Soapfish, Grammistes and Rypticus spp., are bottom-dwelling Perciform Fish related to Groupers, generally found on reefs and other rocky marine environments. They get their common name from their ability to secrete a toxic, soapy, mucus as a defence mechanism. The genus Grammistes is restricted to the Indo-Pacific region, while members of the genus Rypticus are found in the Western Pacific, Atlantic and Caribbean. Only two species of Rypticus have been found on the African coast, the Greater Soapfish, Rypticus saponaceus, and the Spotted Soapfish, Rypticus subbifrenatus. The Greater Soapfish is known from both sides of the Atlantic being found from the coast of Florida, throughout the Caribbean, and as far south as Brazil in the western Atlantic, and from Mauritania south as far as Angola in the eastern Atlantic. However, a genetic study of museum specimens published in 2003 suggested that the eastern and western populations of the Greater Soapfish might in fact be separate species.

In a paper published in the Journal of Fish Biology on 21 July 2025, Gabriel Soares Araujo of the Center for Marine Biology at the University of São Paulo, Cláudio Sampaio of the Laboratório de Ictiologia e Conservação at the Universidade Federal de Alagoas, Luiz Rocha of the  Department of Ichthyology at the California Academy of Sciences, and Carlos Eduardo Ferreira Leite of the Departamento de Biologia Marinha at the Universidade Federal Fluminense, re-examine the genetics of the Greater Soapfish, and formally describe the populations from the African coast as a separate species.

Araujo et al. examined specimens from Cape Verde, Ghana, São Tomé and Príncipe, and Togo. All were found to be genetically distinct from western Atlantic specimens of Rypticus saponaceus, forming a distinct population which is estimated to have split from the west Atlantic population in the Early Pleistocene, about 2.5 million years ago, at the onset of the Pleistocene, and surprisingly being more closely related to the Pacific Rypticus bicolor. Since Rypticus saponaceus was originally described from specimens from Florida, the east Atlantic population is described as a new species, which Araujo et al. name Rypticus africanus.

Time-calibrated phylogeny of the genus Rypticus based on mitochondrial COI gene sequences. Values near the nodes represent estimated divergence times (Mya). The 95% highest posterior density intervals are shown in parentheses. Coloured circles represent the biogeographic regions where species of Rypticus are distributed. Vertical bars depict the results of lineage delimitation tests. Araujo et al. (2025).

Specimens of Rypticus africanus examined range from 112 to 215 mm in length, and have three dorsal fin spines, 22-24 dorsal fin rays, 15-17 anal fin rays, 16-18 pectoral fin rays, and 24-25 caudal (tail) fin rays. The head is distinctly pointed, the dorsal fin originates slightly posterior to upper end the of gill opening, and the tail is rounded. They are brown or dark grey in colour, with numerous pale round spots of variable size on their flanks.

(a)–(c) Rypticus africanus from São Tomé and Príncipe, illustrating the variation in colour pattern between individuals: (a) São Tomé Island, (b), (c) Príncipe Island and (d) Rypticus saponaceus from Salvador, Bahia, Brazil, shown for comparison. Araujo et al. (2025).

Although Rypticus africanus has only been sampled from four areas (Cape Verde, Ghana, São Tomé and Príncipe, and Togo), Araujo et al. believe the name should be applied to all African populations currently described as Rypticus saponaceus, from Mauritania to Angola.

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Saturday, 21 June 2025

Neotrygon romeoi: A new species of Blue-spotted Maskray from Fiji.

Maskrays, Neotrygon spp., are a group of Stingrays, Dasyatidae, found in the Indian Ocean and west Pacific. They get their name from a distinctive coloured marking around the eyes, which resembles a mask, but have a number of other distinctive features, including short tails with well developed dorsal fins, small mouths with enlarged cuspid teeth, and large pectoral fins with a single row of thorns along their dorsal midline. All Maskrays were formerly thought to belong to a single widespread and somewhat variable species, Neotrygon kuhlii, but genetic studies have shown that there are in fact a range of species, with sixteen species described to date, nine of them since 2016, and thirteen of these belonging to a species-complex known as the Blue-spotted group.

In a paper published in the Journal of Fish Biology on 9 June 2025, Kerstin Glaus of the Institute of Marine Resources of The University of the South Pacific, William White and Helen O'Neill of the Australian National Fish Collection, Sarah Thurnheer of the Ecosystems and Landscape Evolution at Eidgenössische Technische Hochschule Zurich, and Sharon Appleyard, also of the Australian National Fish Collection, describe a new species of Maskray from Fiji.

Fiji has long been known to be home to a population of Blue-spotted Maskrays, which are the most widely traded Ray in local fish-markets, but which have never been the subject of a taxonomic study. Glaus et al.'s study was carried out using specimens purchased in Suva Fish Market on Viti Levu Island or obtained from local fishermen. No Rays were killed specifically for the study. A genetic analysis found that these specimens all belonged to a single species, and that this species was previously unidentified, and was a sister species to the previously described Neotrygon kuhlii from the Solomon Islands.

Glaus et al. name this new species Neotrygon romeo, in honour of the late Romeo Glaus, father of Kerstin Glaus, in recognition of his lasting inspiration, enduring support and deep respect for nature. Specimens of Neotrygon romeo have quadrangular disks, weakly convex at the front, and broader than they are long. They range from 310 to 397 mm in width and from 80.6 to 84.2 mm in length, or from 176.9 to 213.1 mm in length including the tail. A single row of thorns is present on the midline. There are two tail stings. Living specimens are beige-to-medium brown, with a slight greenish tinge. The disk has a sparse scaterring of spots, these having a white centre and a diffuse-edged dark-grey to blackishouter ring. There is also a scaterring of smaller, all black, spots. A dark 'mask' is present across the eyesm, and a pair of larger circular or irregular dark brown blotches behind the spiracules. The underside is white. The tail has a bluish tinge, and has irregular black and white bands towards the tip.

Dorsal (a) and lateral (b) view of preserved Neotrygon romeoi holotype (CSIRO H 9640–06, female 379 mm disc width) from Tailevu Province, east Viti Levu Island, Fiji. Scale bar is 50 mm. Glaus et al. (2025).

Neotrygon romeo appears to be common around the islands of Fiji, and is found on various substrates, including sandy-bottom areas, seagrass beds, muddy-sandy areas with and without sea-grass, and coral reefs, from the tidal zone to depths of about 23 m. Individuals are generally solitary, but have been spotted in groups of up to five. Glaus et al. recommend that due to the species restricted range, high catch rate, and unknown life-history, it should be considered for legal protection by Fiji's Endangered and Protected Species Act, which con-serves biodiversity by regulating trade, protection and management of species at risk or endemic to Fiji.

Live colouration of Neotrygon romeoi from around Fiji: (a) Lautoka, mixed rocky and sand habitat. (b) Near South Sea Island, rocky reef. Drawaqa Island, Yasawas on sand flat with some seagrass in about 18 m of water. (d) Suva foreshore, on seagrass in about 20 cm of water. (e) Mana Island, over seagrass. Leon Perrie, Jack Crosbie, Robert Macfarlane, Tom Vierus, and Floyd Hayes in Glaus et al. (2025).

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Sunday, 26 January 2025

Apolithabatis seioma: A new species of stem-group Ray from the Late Jurassic Solnhofen Limestone.

Chondrichthyans, or Cartilaginous Fish, are among the most numerous Vertebrate fossils in the geological record, but almost all these fossils are of isolated teeth. Whole-body fossils of Chondrichthyans, in contrast are extremely rare, limiting our understanding of the morphology and biology of ancient members of this group. 

The oldest known body fossils of Batomorphs, or Rays, date back to the Jurassic Period, considered to be an important interval in Shark and Ray evolution, and come from a series of  'Konservat-Lagerstätten',  the most notable of which is the Solnhofen Limestone, of southern Germany, which records a series of deposits laid down in the Kimmeridgian-Tithonian (i.e. between 154.8 and 143.1 million years ago) in a series of islands, known as the Solnhofen Archipelago, on the edge of the Tethys Sea with many enclosed, placid, lagoons that had limited access to the open sea and where salinity rose high enough that the resulting brine could not support life. The Solnhofen Limestone records a range of Vertebrate fossils in exquisite detail, including Holocephalians (Chimeras), Hybodont Sharks, Selachimorph Sharks, and at least two genera of Batomorphs.

Until fairly recently, all Batomorphs from the Solnhofen Limestone were refered to the genera Asterodermus and Spathobatis, but recent studies have suggested that none of the Solnhoffen specimens can be assigned to Spathobatis, a genus originally described from French specimens, with the German specimens assigned to Spathobatis reassigned to a new genus, Aellopobatis. All known specimens of Asterodermus and Aellopobatis from the Solnhoffen Limestone are thought to be of Tithonian age, although many specimens were collected decades ago from working quarries, and may not be dated accurately.

In a paper published in the journal PLoS One on 23 January 2025, Julia Türtscher and Patrick Jambura of the Department of Palaeontology and the Vienna Doctoral School of Ecology and Evolution at the University of Vienna, Frederik Spindler of PALAEONAVIX, and Jürgen Kriwet, also of the Department of Palaeontology and the Vienna Doctoral School of Ecology and Evolution at the University of Vienna, deescribe a new species of Batomorph from the Kimmeridgian Painten site within the Franconian Alb of central Bavaria.

Geographical setting and stratigraphy of Painten. (A) Geographical map of the ’Solnhofen Archipelago’ and Nusplingen. (B) Stratigraphic section of the Upper Jurassic (upper Kimmeridgian to lower Tithonian) sediments of the ’Solnhofen Archipelago’ (southern Germany), the sequence exposed at Painten is indicated by a bracket. Note that the new Batomorph fossil is from the Ulmense rebouletianum-horizon within the Lithacoceras ulmense Subzone of the Kimmeridgian (highlighted). Türtscher et al. (2025).

The new species is described from a single specimen, DMA-JP-2010/007, and is named Apolithabatis seioma, where 'Apolithabatis' means 'Fossil Ray' in Greek, while 'seioma' derives from the Greek 'seismós', meaning 'shake', in reference to the way in which the fossil was extracted from the rock. The single known specimen of Apolithabatis seioma is at least 120 cm in length, with a heart-shaped disc and a long narrow tail. It has two dorsal fins, both behind the pectoral girdle (i.e. on the tail).

Overview of DMA-JP-2010/007, the holotype of Apolithabatis seioma. (A) Photograph of the specimen. (B) Illustration of the specimen showing the skeletal morphology. Abbreviations: ac, antorbital cartilage; bp, basipterygium; br, branchial arches; c, vertebral centra; cf, caudal fin; d1, first dorsal fin; d2, second dorsal fin; hs, haemal spine; mk, Meckel’s cartilage, ms, mesopterygium; mt, metapterygium; nc, nasal capsule; ns, neural spine; pb, puboischiadic bar; pp, propterygium; pq, palatoquadrate; r, ribs; ra, pectoral fin radials; rap, pelvic fin radials; ro, rostrum; sc, scapulocoracoid; syn, synarcual. The scale bar equals 10 cm. Türtscher et al. (2025).

Previous phylogenetic studies have recovered Jurassic Batomorphs as a part of the crown group (i.e. descended from the last common ancestor of all living members of the group), with the Torpediniformes (Electric Rays) forming the sister group to all other members of the group. However, Türtscher et al. recovered Apolithabatis seiomai, along with the other Jurassic genera Aellopobatis, Asterodermus, Belemnobatis, Kimmerobatis, and Spathobatis, in a distinct clade which has a sister group relationship to all extant Batomoph groups (including the Torpediniformes). Since this implies that this group is not descended from the last common ancestor of all living Batomorphs, Türtscher et al. regard this group, which they name the Order Apolithabatiformes, to stem group Batomorphs.

Majority-rule consensus tree with bootstrap and jackknife frequencies (jackknife values in parentheses). Daggers before taxon names indicate extinct taxa. Türtscher et al. (2025).

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Saturday, 18 January 2025

Plectranthias raki: A new species of Perchlet from the Maldives.

The term 'Perchlet' applies to a wide variety of small Perciform Fish. The genus Plectranthias is a member of the Serranidae, the family which also includes Sea Bass and Groupers, amongst other groups. It currently contains 66 described species from mesophotic reef environments in the Atlantic, Pacific, and Indian Oceans. Plectranthias are small Fish, typically 5-10 cm long with the largest species reaching about 20 cm, which live in holes or crevices, from where they ambush small, mobile invertebrates. The small size and cryptic nature of Plectranthias means that they are not well studied, with most species described from a very small number of specimens.

In a paper published in the journal ZooKeys on 16 January 2024, Bart Shepherd of the Steinhart Aquarium at the California Academy of Sciences, Hudson Pinheiro of the Department of Ichthyology at the California Academy of Sciences, and the Center for Marine Biology at the University of São Paulo, Ahmed Najeeb, also of the Department of Ichthyology at the California Academy of Sciences, and of the Maldives Marine Research Institute, Claudia Rocha, again of the Department of Ichthyology and of the Department of Microbiology at the California Academy of Sciences, and Luiz Rocha, once again of the Department of Ichthyology at the California Academy of Sciences, describe a new species of Plectranthias from the Kuramathi Outer Reef on Rasdhoo Atoll in the Maldives.

The new species is described from two specimens collected by hand-netting at a depth of 118 m, in December 2022, and confirmed as a new species by gene-sequencing. It is named Plectranthias raki, where 'raki' means 'feeling shy to confront people' in the Dhivehi language which is spoken in the Maldives.

Living specimen (not retained) of Plectranthias raki photographed at 110 m depth at Dhaalu Atoll, Maldives. Luiz Rocha in Shepherd et al.  (2025).

The two specimens of Plectranthias raki are 66.15 and 70.41 mm long, and pinkish white in colour with a series of irregular orange-red patches, these being more red towards the tail and more yellow towards the head. Both have dorsal fins with fifteen rays, anal fins with seven rays, pectoral fins with thirteen rays, and tail fins with nine upper rays and eight lower rays.

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Sunday, 22 September 2024

Sueviota aethon: A new species of Dwarf Gobi from the Red Sea coast of Saudi Arabia.

First described in 1988, the Dwarf Gobi genus Sueviota is distinguished from the closely related Eviota on the structure of its pelvic fins. The genus currently contains eight species, found from Papua New Guinea and the northwestern coast of Australia through to the Red Sea.

In a paper published in the journal ZooKeys on 12 September 2024, Viktor Nunes Peinemann and Lucía Pombo-Ayora of the Red Sea Research Center of King Abdullah University of Science and Technology, Luke Tornabene of the School of Aquatic and Fishery Sciences and Burke Museum of Natural History and Culture of the University of Washington, and Michael Berumen, also of the Red Sea Research Center of King Abdullah University of Science and Technology, describe a new species of Sueviota from the Red Sea coast of Saudi Arabia.

The new species is named Sueviota aethon, where 'aethon' derives from Aethon, one of the four Horses which drew the chariot of the Sun God Helios in Greek mythology; it is so named due to its similarity to the previously described Sueviota pyrios; Pyrios having been another of the four Horses. The species is described from ten specimens collected from exposed offshore reefs on the Saudi Arabian Red Sea coast, at depths of between 10 m and 30 m, although Nunes Peinemann et al. note that another specimen was observed at a depth of 53 m.

Holotype specimen of Sueviota aethon (UW 203365), shortly after being collected. Nunes Peinemann et al. (2024).

Specimens of Sueviota aethon are between 9.2 mm and 16.7 mm in length, and most known specimens are dark red in colour (one was a yellow-orange colour). The first dorsal fin is rounded-to-square in shape, with the second and third spines longer than the first. The rays of the second dorsal fin are commonly branched (at least some of these are branched in all known specimens). The body is covered by ctenoid (comb-edged) scales, but these are absent from the head and breast. Two rows of irregularly spaced conical teeth are present on both the lower and upper jaws. Both jaws also have enlarged canine teeth, with these forming part of the outer tooth-row in the upper jaw and the inner tooth-row in the lower jaw.

Micro-CT scan of Sueviota aethon (UW 203365, holotype) showing its osteological characters. (a) Close-up of head showing the enlarged canines on the upper jaw, (b) dentary, showcasing two enlarged canines in the internal row of teeth, (c) lateral view of the complete skeleton. Nunes Peinemann et al. (2024).

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