Revision of the Schistura cincticauda species group (Teleostei, Nemacheilidae) using molecular and morphological markers.

To approach the taxonomy of large and complex animal groups it is of advantage to focus on species groups with shared derived character state. We investigate the composition, morphological characteristics and relationships of and within the Schistura cincticauda species group, whose members are small freshwater fishes that inhabit streams and rivers in eastern Myanmar and western and southern Thailand. A phylogenetic analysis using molecular genetic markers demonstrated the monophyly of this group; a combined genetic and morphological analysis revealed the inclusion of at least twelve species. They share the presence of a pair of black marks on the lower lip, one on each side of the median interruption (these marks may be reduced to few melanophores or even missing in some individuals). Additionally, all species share a small body size (max. 60 mm SL), an incomplete lateral line reaching at most to vertical through anal-fin base, and the absence of sexual dimorphism. Each of the 12 species is diagnosed by a unique combination of character states in fin ray numbers, anus position, presence/absence of an axillary pelvic lobe, and colour pattern. The distribution areas of several species overlap and five cases of syntopic occurrence are known. Five unnamed species are described herein.

Tightening the requirements for species diagnoses would help integrate DNA-based descriptions in taxonomic practice.

Modern advances in DNA sequencing hold the promise of facilitating descriptions of new organisms at ever finer precision but have come with challenges as the major Codes of bionomenclature contain poorly defined requirements for species and subspecies diagnoses (henceforth, species diagnoses), which is particularly problematic for DNA-based taxonomy. We, the commissioners of the International Commission on Zoological Nomenclature, advocate a tightening of the definition of "species diagnosis" in future editions of Codes of bionomenclature, for example, through the introduction of requirements for specific information on the character states of differentiating traits in comparison with similar species. Such new provisions would enhance taxonomic standards and ensure that all diagnoses, including DNA-based ones, contain adequate taxonomic context. Our recommendations are intended to spur discussion among biologists, as broad community consensus is critical ahead of the implementation of new editions of the International Code of Zoological Nomenclature and other Codes of bionomenclature.

Silurichthys exortivus, a new catfish (Teleostei: Siluridae) from eastern Borneo, Indonesia.

Silurichthys exortivus, a new species of silurid catfish, is described from the Mahakam River drainage in eastern Borneo. The new species can be distinguished from congeners in lacking a dorsal fin, having 4 (vs. 67) principal rays on the upper caudal-fin lobe and a combination of: body depth at anus 14.0% SL, caudal peduncle depth 5.1% SL, pelvic fins absent, 54 anal-fin rays, caudal fin with asymmetrical lobes (upper lobe 1.1 times longer than lower), 48 vertebrae, 1 gill raker on the first branchial arch, and a mottled brown body. Based on the reduced number of principal caudal-fin rays, S. exortivus, S. ligneolus and S. sanguineus are hypothesized to form an exclusively Bornean clade.

Nemacheilus pezidion, a new species of loach from southern Laos (Teleostei: Nemacheilidae).

Nemacheilus pezidion, new species, is described from the Xe Kong watershed, Mekong drainage, in Attapeu province, southern Laos. It is distinguished from all other Nemacheilidae in Southeast Asia by its unique colour pattern consisting of a black midlateral stripe and a middorsal row of 1115 narrow saddles. Besides, the male has a globulous suborbital flap with tubercles along its posterior edge, and the pectoral fin with thickened anterior rays, and branched rays 14 and unculiferous pads behind them covered by small tubercles. It was found in habitats with moderate flow, on mud to gravel bottom. Nemacheilus pezidion was earlier misidentified as N. longistriatus.

The trouts of the upper Kura and Aras rivers in Turkey, with description of three new species (Teleostei: Salmonidae).

The taxonomic status of the resident and anadromous trout species native to the Kura and Aras river drainages is evaluated, and three resident species are recognised in the upper reaches of Kura and Aras drainages in Turkey. Salmo murathani, new species, is described from slow flowing tributaries of the Aras River. It is distinguished by the general body color dark greyish in life; the numerous black spots on body, present on the back and on the middle and upper parts of the flank, and on the anterior part of the lower flank in males and females larger than about 230 mm SL; the number of black spots increases with size, in both males and females; and various meristic and morphometric characters. Salmo araxensis, new species, is described from fast flowing tributaries of the Aras River. It is distinguished by the general body color greyish to brownish in life; only few black spots on the body, restricted to the back and the upper part of the flank, their number not increasing with size in both sexes; and various meristic and morphometric characters. Salmo ardahanensis, new species, is described from head waters of the Kura River. It is distinguished by the general body color dark brownish in life; the roundish black spots on the body, scattered on the back, and the middle and upper parts of the flank in most specimens, rarely restricted to the back and the upper part of the flank; in females, the black spots are few, restricted to the back and the upper part of the flank; the number of black spots increases slightly with size in males; the adipose fin is large, almost reaching to caudal-fin base in males larger than about 170 mm SL; and various meristic and morphometric characters.

Pseudobagarius eustictus, a new species of catfish from northern Laos (Siluriformes: Akysidae).

Pseudobagarius eustictus, new species, is described from the Nam Heung drainage (a tributary of the Mekong River) in northern Laos. It is distinguished from congeners in having a unique combination of the following characters: a weakly-produced snout in which the upper jaw extends only slightly beyond the margin of the lower jaw when viewed ventrally, 3 tubercles on the posterior margin of the pectoral spine, eye diameter 8% HL, head width 24.1% SL, dark yellow dorsal and lateral surfaces of the head, pectoral spine lacking elongate extensions, pectoral fin reaching the pelvic-fin base when adpressed against the body, dorsolateral surfaces of body without longitudinal series of prominent tubercles, body depth at anus 13.7% SL, length of adipose-fin base 17.7% SL, caudal-peduncle depth 7.0% SL, and 33 vertebrae.

A note on emMuraena/em emalba/em Zuiew, 1793 (Teleostei: Synbranchidae).

Originally described as Muraena alba by the Russian ichthyologist Basilius Zuiew (1793) [Vasilij Fyodorovich Zuev'], the name Monopterus albus has long been used for a species of swamp eel (Synbranchidae) with a reportedly widespread occurrence in Asia (Rosen Greenwood 1976, Kottelat 2013). In recent years molecular studies have shown that Monopterus albus of authors is a species complex and several authors have recommended that up to three (Collins et al. 2002, Matsumoto et al. 2010, Kottelat 2013, Nico et al. 2019) or even five (Arisuryanti 2016) different species can be recognized. Kottelat (2013) referred to the eastern Asian clade of Matsumoto et al. (2010) as Monopterus albus and the Southeast Asian clade as Monopterus javanensis La Cepède, 1800, noting that no name is available for the clade on the Ryukyu Islands.

Description of Bagarius vegrandis, a new species of sisorid catfish from Indochina (Actinopterygii: Siluriformes), with notes on the identity of Bagarius bagarius.

Bagarius vegrandis, new species, is described from the Chao Phraya and Mekong river drainages. It differs from congeners in having a small maximum body size (to 220 mm SL vs. 520-1400 mm SL) and the adipose-fin origin markedly posterior to (vs. at vertical through or very slightly posterior to) the anal-fin origin. It further differs from congeners in having the following unique combination of characters: ovoid unculiferous plaques on dorsal surface of head, lateral margin of frontal not significantly deflected dorsally, eye diameter 11-15% HL, interorbital distance 23-28% HL, head width 18.3-22.3% SL, head depth 11.1-14.1% SL, filamentous extensions to first pectoral-fin element reaching to anus, dorsal spine width 10.6-13.9 times in its length, body depth at anus 8.7-12.0% SL, neural spines of the 4-6 vertebrae immediately anterior to adipose fin distally flattened but not forming series of prominent bumps along dorsal midline, length of adipose-fin base 10.8-13.0% SL, caudal-peduncle length 19.0-22.4% SL, caudal-peduncle depth 3.2-4.2% SL, 19-20 preanal vertebrae, and 39-40 total vertebrae. Bagarius bagarius (Hamilton, 1822) is demonstrated to be a species restricted to the Indian subcontinent (with Bagrus yarrelli Sykes, 1839, Pimelodus platespogon Valenciennes, in Jacquemont, 1839 and Pimelodus carnaticus Jerdon, 1849 as junior subjective synonyms) and Bagarius lica Volz, 1903 resurrected from synonymy with B. yarrelli as a valid species from Southeast Asia.

'Nemacheilus' argyrogaster, a new species of loach from southern Laos (Teleostei: Nemacheilidae).

'Nemacheilus' argyrogaster, new species, is described from the Xe Kong, Mekong drainage, in Attapeu and Xe Kong provinces, southern Laos. It is distinguished from all other Nemacheilidae in Southeast Asia by its unique colour pattern made of a bold black midlateral stripe separating the yellowish brown dorsal part of the body from the silvery whitish ventral part and a middorsal row of 14-19 thin saddles. Besides, the male has a globulous suborbital flap with tubercles along its free, posterior edge, and the pectoral fin with thickened anterior ray and branched rays 1-4 and unculiferous pads behind them covered by small tubercles; lips thin, lower lip continuous with a narrow median notch. It was found in moderate to fast flowing water, over pebble to stone bottom. 'Nemacheilus' argyrogaster, was earlier misidentified as N. longistriatus; it is provisionally placed in the genus Nemacheilus.

One northward, one southward: Contrasting biogeographical history in two benthic freshwater fish genera across Southeast Asia (Teleostei: Cobitoidea: Nemacheilus, Pangio).

Southeast Asia is one of the world's biodiversity hotspots, and the high level of diversity and endemism was reached by colonisation events as well as internal diversification. We investigate the phylogenetic relationships and biogeographic history of the loach genus Nemacheilus, which is widely distributed and common across freshwaters of Southeast Asia. In addition we present the ancestral range reconstruction of the related loach genus Pangio that commonly occurs in the same region as Nemacheilus. Our results reveal that the species currently classified as Nemacheilus in fact are a polyphyletic assemblage; most species are now retaining in a monophyletic Nemacheilus sensu stricto and five species belong to different lineages. We further indicate the existence of hidden diversity within Nemacheilus in the form of several undescribed species. Three major clades (Selangoricus, Masyae and Ornatus) are found within the genus Nemacheilus sensu stricto. These clades generally correspond to the species groups formerly defined on the basis of their pigmentation pattern. The biogeographic analyses show that Nemacheilus most likely originated in mainland Southeast Asia and subsequently expanded in a southward direction to Borneo, Sumatra and Java and the southern Malay Peninsula. In contrast, the genus Pangio originated in Sundaland, from where it extended several times northwards into Indochina and to northern India. Our results demonstrate that small freshwater fishes with restricted dispersal ability are very helpful for the reconstruction of biogeographic history. The contrasting biogeographic history of these two groups of small, benthic and related fish show how complex and case-specific the processes that lead to the biodiversity richness of Southeast Asia are.

Nomenclatural status and possible identity of Aperioptus pictorius (Teleostei: Gonorynchidae [?] and Cobitidae).

Richardson (1848) described Aperioptus pictorius based on two syntypes from "Borneo". The description is based partly on a drawing of the whole fish and a close-up of its mouth parts (Fig. 1b). Richardson explained that at the time of writing the description, he no longer had access to the specimens: he had given them to the artist, after having examined them cursorily. After having made the first sketch, the artist placed them in water to have the fins expanded, then forgot about them when he threw out the water, and they were lost. The whole description reads: "The general aspect of the fish is that of a slender Galaxias, but there are no teeth on the jaws. The orifice of the mouth is a narrow vertical oval, which is restricted on the sides by membranous processes. The figure is of the natural size [about 65 mm SL]. Hab. Borneo". He also indicated:.

Rhyacoschistura larreci, a new genus and species of loach from Laos and redescription of R. suber (Teleostei: Nemacheilidae).

Rhyacoschistura, new genus, belongs to a group of genera (Physoschistura, Mustura, Pteronemacheilus, Petruichthys) characterised by the modified branched pectoral-fin rays of males, with a very thick first ray, usually without membranes between some of the branches and/or rays, and anterior rays and/or membranes covered by small tubercles at maturity. Rhyacoschistura is distinguished from them by the combination of: presence of a suborbital flap; emarginate caudal fin; lower lip with a wide median interruption and connected to isthmus by a frenum; body depth about equal from behind head to caudal-fin base. Rhyacoschistura larreci, new species, is described from the Mekong drainage in Xayaburi Province, Laos. It is distinguished by details of the morphology of the pelvic fin, and its colour pattern (flank with numerous narrow slanted bars, very irregularly organised and shaped, more or less connected, or sometimes covering the whole flank). Schistura suber, from Nam Ngum watershed, is redescribed on the basis of adults and placed in Rhyacoschistura.

Speolabeo, a new genus name for the cave fish Bangana musaei (Teleostei: Cyprinidae).

Speolabeo, new genus, is established for Bangana musaei, a fish from caves in the Khammouan Karst in Laos. It was originally tentatively placed in the genus Bangana s.l. Besides characters related to hypogean life (absence of eyes, absence of pigment resulting in a whitish body), it is distinguished from all species of Bangana s.l. in having only 7-8½ branched dorsal-fin rays, the pelvic-fin at the vertical between the first unbranched and first branched dorsal-fin rays, and details of mouth morphology.

The Glyptothorax of the Bolaven Plateau, Laos (Teleostei: Sisoridae): new and endangered.

Glyptothorax forabilis, new species, and G. porrectus, new species, are described from the Bolaven Plateau in southern Laos. Both species closely resemble G. laosensis, but can be distinguished from it and other Indochinese congeners by combinations of color pattern, morphometry (with particular regards to the eye, body depth, and caudal peduncle) and thoracic adhesive apparatus morphology. Both species are endemic to the Bolaven Plateau, have a very limited distribution and are threatened by hydropower and agricultural activities.

The Glyptothorax of Sundaland: a revisionary study (Teleostei: Sisoridae).

The species of Glyptothorax of Sundaic Southeast Asia (Malay Peninsula, Sumatra, Borneo and Java) are revised in this study. A total of 17 species are recognized, of which six (G. amnestus, G. decussatus, G. famelicus, G. keluk, G. pictus and G. stibaros) are described as new here. A lectotype is designated for G. platypogon. The Sundaic Glyptothorax species are diagnosed by combinations of color pattern, morphometry (with particular regard to the eye, head, body depth, and caudal peduncle), dorsal-spine and thoracic adhesive apparatus morphology.

On Gonorynchus, Gonorhynchus, Gonorinchus, Gonorhinchus and Gonorrhynchus, and some other names of labeonine fishes (Teleostei: Gonorynchidae and Cyprinidae).

The supposed cyprinid genus 'Gonorhynchus McClelland, 1838' does not exist; the name refers to Gonorhynchus Cuvier, 1816, which is a junior objective synonym of Gonorynchus Scopoli, 1777. The correct family-group name, authorship and date are: Gonorynchidae Fowler, 1941 (1848). Tariqilabeo Mirza & Saboohi, 1990 is the valid genus name for the South Asian species earlier placed in Crossocheilus or 'Gonorhynchus'. The family-group names Garrae Bleeker, 1863 and Labeonini Bleeker, 1859 are declared nomina protecta and Platycarinae Macleay, 1841 is declared nomen oblitum.

Clarias serniosus, a new walking catfish (Teleostei: Clariidae) from Laos.

Clarias serniosus, a new Southeast Asian walking-catfish species, is described from the Bolavens Plateau in southern Laos. The new species is a member of the C. batrachus species complex, and can be distinguished from congeners in the complex in having a combination of: occipital process length 15-17 % HL, head length 28.2-28.6% SL, head width 18.5-19.2% SL, head depth 13.0-13.7% SL, distance between the occipital process and the base of the first dorsal-fin ray 8.5% SL, smooth anterior edge of pectoral spine, 67 dorsal-fin rays, body depth at anus 16.2-16.5% SL, and 57 total vertebrae.