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(A) Schistura ataranensis, Myanmar: Kayin Province: Ataran drainage; (B) S. hartli, Thailand: Surat Thani Province: Khao Sok; (C) S. myaekanbawensis, Myanmar: Tanintharyi Region: Tanintharyi drainage; (D) S. kuehnei, Thailand: Surat Thani Prov.: Tapi drainage, Khlong Sok watershed;. (E) S. peninsulae, Malaysia: Kedah Prov.: Langkawi Island. Dvořák, Jörg Bohlen, Maurice Kottelat and Vendula Šlechtová. 2023 Revision of the group (, ) using and markers. Scientiports. 13: 16996. |
Abstract
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.
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Species of the cincticauda species group described before 2023: (A) Schistura aurantiaca, CMK 14530, 45.8 mm SL; Thailand: Kanchanaburi province: Mae Khlong basin; (B) Schistura balteata, CMK 17236, 53.5 mm SL; Thailand: Kanchanaburi province: Mae Khlong basin: Pilok stream; (C) Schistura cincticauda, ZRC 38458, neotype, 29.3 mm SL; Thailand: Tak province: Salween basin: Moei River; (D) Schistura crocotula, CMK 16458, 30.4 mm SL; Thailand: Prachuap Khiri Khan province; (E) Schistura paucifasciata, BMNH 1930.3.3:4, paratype, 46.6 mm SL: Myanmar: Monglong; (f) Schistura robertsi, CMK 5346, paratype, 30.0 mm SL; Thailand: Phang Nga province: Phang Nga basin; (G) Schistura tenebrosa, UF 181417, holotype, 45.1 mm SL: Thailand: Kanchanaburi province: Mae Khlong drainage. (from Kangrang et al. 2012). |
The Schistura cincticauda species group
Schistura aurantiaca Plongsesthee, Page & Beamish, 2011
Schistura balteata (Rendahl, 1948)
Schistura cincticauda (Blyth, 1860)
Schistura crocotula Plongsesthee, Kottelat & Beamish, 2013
Schistura paucifasciata (Hora, 1929)
Schistura robertsi Kottelat, 1990
Distribution: Widely distributed in most drainages of the Andaman Sea slope of Thailand, from the Isthmus of Kra southwards to Phuket Island. It was also found in some localities east of the Tenasserim Range in the upper Khlong Sok and upper Tapi River, which drain to the Gulf of Thailand, and in the Krabi River basin (Fig. 7). It occurs in sympatry with S. kuehnei in the upper Khlong Sok and with S. peninsulae in the upper Tapi.
Schistura tenebrosa Kangrang, Page, Beamish, 2012
Schistura ataranensis, new species
Distribution Known only from the upper Ataran River drainage, in Myanmar.
Etymology Named after River Ataran, where the type series was collected. An adjective, -is, -is, -e.
Remarks Schistura ataranensis is traded as ornamental fish since at least 2006 under names like ‘Sumo loach’, ‘Sumo loach II’, ‘Schistura cf. balteata’22. However, pictures of fishes from the ornamental fish trade suggest that additional species are confused under these names.
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The new species described in the present study. (A) Schistura ataranensis, ZRC 61579, holotype, 43.5 mm SL; Myanmar: Kayin province: Ataran drainage; (B) Schistura hartli, ZRC 61581, holotype, 41.0 mm SL; Thailand: Surat Thani Province: Khao Sok; (C) Schistura myaekanbawensis, MHNG 2790.081, holotype, 29.8 mm SL; Myanmar: Tanintharyi Region: Tanintharyi drainage; (D) Schistura kuehnei, ZRC 61582, holotype, 37.1 mm SL; Thailand: Surat Thani Province: Tapi drainage, Khlong Sok watershed;. (E) Schistura peninsulae, ZRC 61584, holotype, 35.6 mm SL; Malaysia: Kedah province: Langkawi Island. |
Schistura hartli, new species
Distribution Known only from three specimens, collected in Khao Sok NP in a small forest stream (Fig. 7). Exact position of the locality unknown.
Etymology Named for Andreas Hartl, who collected the type material. Noun in genitive, indeclinable.
Schistura myaekanbawensis, new species
Schistura kuehnei, new species
Distribution Known only from a small forest stream draining from Khao Sok NP into stream Khlong Sok (River Tapi drainage) in Surat Thani province (Fig. 7); at the type locality it co-occurs with S. robertsi.
Etymology Named after Jens Kühne, in acknowledgement of his long-time support of our ichthyological work in Southeast Asia. Noun in genitive, indeclinable.
Schistura peninsulae, new species
Etymology Named after its wide distribution on the Malay Peninsula; it also is the most southern species of Schistura on the Malay Peninsula. A noun in genitive, indeclinable.
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Bayesian tree of the concatenated dataset (mitochondrial cytochrome b plus nuclear IRBP 2 genes) showing the phylogenetic relationships of the species of the Schistura cincticauda species group and the proposed position of S. paucifasciata as concluded from its shared rare pigmentation element with S. balteata. The Bayesian (BAY) and maximum likelihood (ML) analyses revealed congruent topologies; the rectangles at the nodes indicate the posterior probabilities and bootstrap support. The map indicates the geographic origin of the analysed samples of the species. Colours in the tree correspond to colours in map; the values at the nodes represent the posterior possibilities. |
Tomáš Dvořák, Jörg Bohlen, Maurice Kottelat and Vendula Šlechtová. 2023. Revision of the Schistura cincticauda species group (Teleostei, Nemacheilidae) using molecular and morphological markers. Scientific Reports. 13: 16996. DOI: 10.1038/s41598-023-42852-1
