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

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.

Full text

1
Vol.:(0123456789)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports
Revision of the Schistura
cincticauda species group
(Teleostei, Nemacheilidae) using
molecular and morphological
markers
Tomáš Dvořák 1,2, Jörg Bohlen 1*, Maurice Kottelat 3,4 & Vendula Šlechtová 1
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 shes 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-n base, and the absence of sexual dimorphism.
Each of the 12 species is diagnosed by a unique combination of character states in n ray numbers,
anus position, presence/absence of an axillary pelvic lobe, and colour pattern. The distribution areas
of several species overlap and ve cases of syntopic occurrence are known. Five unnamed species are
described herein.
e freshwater sh family Nemacheilidae inhabits nearly the whole of Eurasia, and with > 700 species in about
50 genera is one of the largest in Eurasia1,2. However, still new species and genera are regularly described1,3–9.
With > 230 described species, the genus Schistura is the largest genus of Nemacheilidae, and it is distributed
across most of South and Southeast Asia2,10. It is well known that Schistura is a polyphyletic assemblage, a ‘catch-
all genus’2,4,11–14, but the high number of species and the wide distribution have hampered a global revision of
the genus. Few researchers have tried to identify natural groups of related species of manageable size within the
genus in order to analyse their taxonomy and, biogeography, and to contribute to their conservation. is is an
unfortunate situation and experience shows that it is feasible to distinguish a number of groups of species that
share distinctive morphological feature11,15,16. It is predictable that several such species groups might once be
recognised as distinct genera. In the present study we focus on the Schistura cincticauda species group, which
is distributed in eastern Myanmar and western and southern ailand (Fig.1). e existence of a species group
made of S. cincticauda and related species was rst noted, based on morphological data, by Kottelat11 and more
recently dened by genetic data15. is recent analysis found ten species in the group, each well supported by
mitochondrial and nuclear data. In this genetic study, the group was referred to as the ‘Schistura robertsi g ro up’,
it is more appropriate, following practices in ichthyology, to use the name of the oldest member, S. cincticauda,
as name for the group.
Most species of the S. cincticauda species group inhabit very small to medium streams. Some species like S.
ataranensis, S. aurantiaca and S. balteata are found mainly in the upper reaches of streams. e smallest species
(S. hartli, S. kuehnei, S. peninsulae, S. robertsi) are regularly found in very small forest streams, in shallow water,
among leave litter. ese headwater habitats have a high degree of isolation from each other, and are occupied
OPEN
1Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Rumburská 89, 277 21 Liběchov, Czech
Republic. 2Department of Zoology, Faculty of Science, Charles University, Viničná 7, 128 00 Prague 2, Czech
Republic. 3Delémont, Switzerland. 4Lee Kong Chian Natural History Museum, National University of Singapore, 2
Conservatory Drive, Singapore 117377, Singapore. *email: joerg_bohlen@yahoo.de
Content courtesy of Springer Nature, terms of use apply. Rights reserved

2
Vol:.(1234567890)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
by very small sh populations. erefore the impact of genetic dri and local adaptation can be expected to be
high in the S. cincticauda species group, leading to a fast and geographically small-scaled evolution. e pre-
sent study aims to test the monophyly of the S. cincticauda group with a larger number of species, to provide
a morphological diagnosis, identify the species belonging to the group, review their morphology and describe
the unnamed species.
Methods
About 300 specimens of the S. cincticauda group were examined, including the complete set of specimens ana-
lysed by Bohlen etal.15. Specimens were either xed in 4% formaldehyde and stored in 70% ethanol or xed and
stored in 96% ethanol. Method for measurements and counts follow Kottelat11. e phylogenetic trees have been
recalculated using the dataset from Bohlen etal.15 plus the cytochrome b sequence of S. tenebrosa (GenBank
accession number JQ659026) and sequences of 54 species of Schistura and of 23 species from other nemacheilid
genera from GenBank (Supplementary Material TableS1). Method of Bayesian analysis, StarBEAST species tree
calculation and maximum likelihood tree reconstruction followed Bohlen etal.15. Genetically analysed specimens
of the ingroup were grouped into their clades and searched for inter-clade dierences in morphology. Candidate
characters were evaluated and checked on the non-sequenced specimens. For details of morphological characters
for the new species see Supplementary material. Collection abbreviations: BMNH, Natural History Museum,
London, UK;CMK, Collection of Maurice Kottelat, Delémont, Switzerland; IAPG, Collection of the Institute
of Animal Physiology and Genetics, Liběchov, Czech Republic; MCZ, Museum of Comparative Zoology, Har-
ward University, Cambridge, USA; MHNG, Muséum d’Histoire Naturelle, Geneva, Switzerland; UF, University
of Florida, Gainsville, USA; ZRC Zoological Reference Collection, Lee Kong Chian Natural History Museum,
National University of Singapore, Singapore.e publication is registered in ZooBank under the number LSID
urn:lsid:zoobank.org:pub:431013B9-DF21-4078-BFE8-C7BE622492D5.
Figure1. 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.
e Bayesian (BAY) and maximum likelihood (ML) analyses revealed congruent topologies; the rectangles at
the nodes indicate the posterior probabilities and bootstrap support. e 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.
Content courtesy of Springer Nature, terms of use apply. Rights reserved

3
Vol.:(0123456789)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
Results and discussion
The Schistura cincticauda species group
e reconstructed phylogeny including 11 species of the S. cincticauda species group plus 77 other species of
Nemacheilidae demonstrated the monophyly of the S. cincticauda species group (Fig.2). e combined results
from genetic and morphological analyses show that the S. cincticauda group contains at least 12 species, seven
of them with a valid name [S. aurantiaca Plongsesthee etal., 2011, S. balteata (Rendahl, 1948), S. cincticauda
(Blyth, 1860), S. crocotula Plongsesthee etal., 2013, S. paucifasciata (Hora 1929), S. robertsi Kottelat, 1990 and
S. tenebrosa Kangran etal., 2012] and ve unnamed species. Genetic data were available for all but one (S. pau-
cifasciata) of these species.
Externally, the species of the group share one synapomorphy: the presence of two black marks on the lower
lip, one on each side of the median interruption (Fig.3). ese marks are located in a deeper layer of the skin
than the general pigmentation of the head and are always black, while the general head and body pigmentation
can be dark grey or brown. While the general head and body pigmentation may fade when the live sh is stressed,
or change during xation or aer long time storage, the black marks on the lower lip prove to be much more
stable and are visible in nearly all of about 300 analysed specimens, including specimens preserved more than
50years ago. e stability of the black marks on the lower lip resembles that of the black marks on the base of
the caudal n or on the rst rays of the dorsal n in most species of Nemacheilidae, which is known to survive
in many museum specimens, including material collected in the early nineteenth century (MK, pers. observ.).
e position of the black marks on the lower lip varies between species of the group, ranging from close to the
median interruption of the lip (S. peninsulae; Fig.3J) to almost halfway between median interruption and corner
of mouth (S. hartli; Fig.3F). e marks vary in size and intensity: in S. cincticauda the marks are only weakly
developed (Fig.3D); oen consisting of only a few melanophores on one side of the lip and easily overlooked,
while in S. kuehnei and S. robertsi they are prominent black blotches that stretch along one third of the lower-lip
Figure2. Maximum Likelihood phylogenetic tree showing the monophyly of the Schistura cincticauda species
group (indicated by red arrow). Besides the 11 species of the Schistura cincticauda group for which genetic data
are available (underlaid with yellow colour), the analysis covered 54 additional species of the genus Schistura
(species names and branches in black) and 23 species of other nemacheilid genera (species names and branches
in red). e tree was rooted with Cobitis taenia. e values at the nodes represent relevant statistical supports in
percentages of 5000 bootstrap replicates. Values lower than 70% are not shown.
Content courtesy of Springer Nature, terms of use apply. Rights reserved

4
Vol:.(1234567890)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
(Fig.3G,K). In S. crocotula and S. myaekanbawensis, a second pair of black marks is located on the lower lip,
at the corner of mouth (Fig.3E,H). Our material of S. balteata originated from two localities; one in Myanmar
(details not known) and one in the upper Mae Khlong basin in ailand. While the marks are present in all four
specimens from Myanmar and two specimens from the ai locality (Fig.3C), they are missing in the remaining
four specimens from the ai locality (not shown). e presence of black marks could not be conrmed in the
only investigated specimen of S. paucifasciata (collected in 1911), in which the lower lip is pulled backwards (a
xation artefact or the result of desiccation, before we examined it in 1989) (Fig.3I). We are not aware of any
species of Schistura s.l. outside the S. cincticauda group with such marks on the lower lip, thus they appear to be
a synapomorphy of the group. Despite their occasional absence, or diculties to observe them, they represent
the easiest external diagnostic character of the S. cincticauda group.
Although the black marks are not visible in the only available specimens of S. paucifasciata we consider this
species to belong to the cincticauda group on the basis of the following reasons: S. paucifasciata shares with S.
Figure3. Ventral view of the mouth of the twelve species presently assigned to the Schistura cincticauda species
group. Red arrows indicate the characteristic pair of black blotches on the lower lip, blue arrows indicate an
additional pair of black blotches on the lower lip. (A) S. ataranensis, ZRC 61579, holotype, 43.8mm SL; (B) S.
aurantiaca, IAPG A11272-11,274, 27.0mm SL; (C) S. balteata, IAPG A2554, 32.2mm SL; (D) S. cincticauda,
IAPG A8313, 30.0mm SL; (E) S. crocotula, IAPG A10513-10,517, 35.5mm SL; (F) S. hartli, CMK 28810,
paratype, 36.6mm SL, blue outline depicts the diagnostic black mark posterior of the median incision; (G) S.
kuehnei, ZRC 61582, holotype, 37.1mm SL; (H) S. myaekanbawensis, CMK 24993, paratype, 29.4mm SL; (I) S.
paucifasciata, BMNH 930.3.3.4, paratype, 46.6mm SL, blue dotted line shows anterior margin of lower lip; (J) S.
peninsulae, IAPG A11506, 33.8mm SL; (K) S. robertsi, IAPG A10967, 31.4mm SL; (L) S. tenebrosa, UF 181418,
paratype, 33.2mm SL.
Content courtesy of Springer Nature, terms of use apply. Rights reserved

5
Vol.:(0123456789)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
balteata the unusual colour pattern of having only few narrow, black, contrasting bars in the middle of the ank
and the rest of the ank light brown. In both species the dorsal adipose crest on the caudal peduncle is higher
and the axillary pelvic lobe larger than in other species of the group. It shares with all species of the cincticauda
group an incomplete lateral line, a small body size and an emarginate caudal n. Kottelat11 already noted that
the colour pattern of juveniles (gured by Hora17) has some similarities with that of S. cincticauda (and also S.
aurantiaca described inbetween). Since S. paucifasciata and S. balteata are the only two species of Schistura with
the above described colour pattern we consider them to represent sister species. us the phylogenetic position
of S. paucifasciata is indicated in our phylogenetic reconstruction as sister to S. balteata (Fig.1). e aliation
of S. tenebrosa to the cincticauda group is demonstrated by its black marks on the lower lip and genetic data.
A few other species have been suggested to be closely related to S. cincticauda. Kottelat11 listed S. cincticauda,
S. robertsi, S. daubentoni and possibly S. paucicincta, S. paucifasciata, S. kangjupkhulensis and S. malaisei. We
conrm here that S. robertsi and S. paucifasciata belong to the S. cincticauda species group. Our genetic data
(Fig.2) show that S. paucicincta and S. malaisei do not belong to this group. Schistura daubentoni does not have
black marks on the lower lip; it has tubercles on the dorsal side of the pectoral n. Both character states are
not congruent with the S. cincticauda species group; therefore we exclude it from this group. Only gures were
available of S. kangjupkhulensis, which did not allow to conclude on the phylogenetic position of the species; its
evaluation has to await further data.
Additionally, the species of the S. cincticauda species group are characterised by the combination of the fol-
lowing features: a small size (less than 60mm SL); an incomplete lateral line reaching at most to vertical through
the anal-n base; a relatively deep caudal peduncle with dorsal and ventral crests; a truncate or emarginate caudal
n (never forked); the anterior nostril with a ap-like tube that reaches at least to anterior margin of eye; and
absence of sexual dimorphism (no morphological dierences in the pectoral ns, no suborbital ap). Most spe-
cies also have a comparably low number of branched rays in pectoral and caudal n. However, although useful
for identication in combination, these character states are not restricted to species of the S. cincticauda group,
but some appear in several other species and lineages of Schistura.
Most species of the S. cincticauda group have a prominent thick dark bar at caudal-n base, reaching onto
ventral and dorsal adipose crests. However there are exceptions; in S. balteata (Fig.4B) the black bar is completely
absent and in S. kuehnei (Fig.5D) it is thin and interrupted in its upper third. e body colour pattern of most
species of the S. cincticauda group consists of grey to black bars on a lighter background. In most species this pat-
tern is already observed in juveniles. However, in S. balteata and S. paucifasciata, most bars become less sharply
contrasted with growth until only 2 to 4 narrow black bars remain in the middle region of the ank, while the
rest of the ank is light brown (11, pers. observ., Fig.4B,E). In other species, some bars may fuse entirely, so that
parts of the ank appear uniformly dark. In S. kuehnei the bars on the caudal peduncle are fused, while in many
specimens of S. aurantiaca and both S. hartli bars in the anterior part of the ank are fused; and in S. crocotula,
S. peninsulae and S. robertsi the partial or complete fusions of bars may be observed on any part of the ank.
Figure4. Species of the cincticauda species group described before 2023: (A) Schistura aurantiaca, CMK
14530, 45.8mm SL; ailand: Kanchanaburi province: Mae Khlong basin; (B) Schistura balteata, CMK 17236,
53.5mm SL; ailand: Kanchanaburi province: Mae Khlong basin: Pilokstream; (C) Schistura cincticauda, ZRC
38458, neotype, 29.3mm SL; ailand: Tak province: Salween basin: MoeiRiver; (D) Schistura crocotula, CMK
16458, 30.4mm SL; ailand: 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; ailand:
Phang Nga province: Phang Nga basin; (G) Schistura tenebrosa, UF 181417, holotype, 45.1mm SL: ailand:
Kanchanaburi province: Mae Khlong drainage. (from Kangrang etal. 2012).
Content courtesy of Springer Nature, terms of use apply. Rights reserved

6
Vol:.(1234567890)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
In S. ataranensis the bars are fused and most of the ank is brown, leaving only few interspaces in the middle
region of the ank. In S. tenebrosa all bars have fused and the ank is plain brown. e extensively broad dark
bars interrupted by few interspaces as observed in S. ataranensis and some S. aurantiaca has erroneously been
described as a dark body with light bars.
In the species of the S. cincticauda group the interspaces tend to be more colourful than in most other species
of Schistura. While being light brown or cream white in most Schistura species, all or some interspaces are pink,
orange or purple in S. aurantiaca, some S. balteata, S. crocotula, S. hartli, S. ataranensis and S. kuehnei.
Species of the S. cincticauda group have in common a similar body shape with a nearly cylindrical anterior
part of the body, a relatively high caudal peduncle with dorsal and ventral crests and short ns with rounded
tips. is similar body shape in combination with the small size and oen not straight shape of many museum
specimens, their dierent xation history (ethanol or formalin, concentration, age) made morphometric char-
acters nearly uninformative in the available material (therefore detailed descriptions of the body shape are given
in Supplementary Material).
Characters for species diagnosis
e observed character states that are useful to diagnose species and their expression in each species is given in
Table1 and visualised in Fig.6. e overview of all variable characters and all species of the S. cincticauda species
group allows direct one-to-one comparison of the species.
Species overview
Schistura aurantiaca Plongsesthee, Page & Beamish, 2011 (Fig.4A, Table1)
Diagnosis Schistura aurantiaca is distinguished from all species in the S. cincticauda species group by the com-
bination of the following character states: axillary pelvic lobe absent; bases of unbranched and rst branched
dorsal-n rays with prominent black blotch; broad black bar on base of caudal n; 9 + 8 branched rays in caudal
n, 9 rays in pectoral n; colour pattern consisting in 4–12 dark brown bars and 5–11 regular orange interspaces;
rst interspace slightly before dorsal-n base; 1–2 interspaces under and one slightly behind dorsal-n base;
sometimes additional 2–5 irregular light orange interspaces on caudal peduncle and 2–4 irregular light orange
interspaces between head and dorsal n; anus midway between posterior extremity of pelvic-n base and anal-
n origin; incomplete lateral line, reaching to vertical through origin of dorsal n; colour pattern in smallest
examined specimens (20–25mm SL) already as in adults.
Distribution Known from upper Khwae Noi and upper Khwae Yai (Mae Khlong river basin), from upper
Moei (Salween river basin), and upper Ataran.
Remarks Although formally named only in 2011 by Plongsesthee, Page & Beamish18 S. aurantiaca had
already been described and gured by Rendahl19 under the name S. cincticauda, on the basis of material from
Sukli (16°41′35″N 98°21′56″E), a village on the eastern slope of Dawna Hills about 20km west of Mae Sot
(ailand), in the watershed of Moei River (Salween drainage). e described material can be identied as S.
aurantiaca by the colour pattern (presence of 10–12 black bars on body in at least small specimens vs. 6–8 bars
in S. cincticauda). Moreover, the larger specimens in Fig.18 of Rendahl19 show the typical colour pattern of
adult S. aurantiaca. Hora17 also reported S. cincticauda from Sukli, but his description and gure do not allow
an unambiguous identication.
Figure5. e 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; ailand: Surat ani 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; ailand: Surat ani Province: Tapi drainage, Khlong Sok watershed;. (E) Schistura peninsulae,
ZRC 61584, holotype, 35.6mm SL; Malaysia: Kedah province: Langkawi Island.
Content courtesy of Springer Nature, terms of use apply. Rights reserved

7
Vol.:(0123456789)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
Schistura balteata (Rendahl, 1948) (Fig.4B, Table1)
Diagnosis Schistura balteata is unique among Nemacheilidae by its adult colour pattern consisting of 2–4 thin
black bars below dorsal-n base and 3–5 saddles in front of dorsal n; the rest of the body is cream-brown; no
black caudal bar. Most similar is S. paucifasciata, which shares with S. balteata the presence of 2–4 thin black
bars on an otherwise light brown body. Schistura balteata diers from S. paucifasciata by not having a dark bar
at base of caudal n and by presence of 3–5 saddles. Additionally S. balteata is characterised by a combination
of the following character states: axillary pelvic lobe present; absence of prominent black mark on anterior part
of dorsal-n base; 8 + 8 branched rays in caudal n, 10–11 rays in pectoral n; anus midway between posterior
extremity of pelvic-n base and anal-n origin; incomplete lateral line reaching above anal-n base.
Distribution Known from the type locality (Mahlve Taung mountain range in Tenasserim, Myanmar) and
upper Khwae Noi (Mae Klong drainage, ailand).
Table 1. Comparison of selected morphological characters between the 12 species of the Schistura cincticauda
species group. * Data taken from Hora 1929 and Kottelat 1990; ** Data taken from Kangrang etal. 2012; ***
“short” = ending before middistance from pectoral to pelvic-n base, “intermediate” = ending slightly before
dorsal-n origin or under rst or second branched ray of dorsal n, “long” = ending behind dorsal n base.
S.
aurantiaca S. balteata S.
cincticauda S. crocotula S. hartli S.
ataranensis S.
myaekanbawensis S. kuehnei S. robertsi S.
paucifasciata * S.
peninsulae
S.
tenebrosa
**
n 34 9 2 18 2 11 5 11 46 1 53 36
SL (mm) 21.7–45.4 29.7–57.3 27.9–30.0 17.1–44.8 36.1–41.0 34.9–43.5 36.1–41.0 22.8–29.8 19.5–32.5 46.6 20.5–49.0 32.0–46.0
Anal n
rays 3/51/23/51/23/51/23/51/23/51/23/51/23/51/23/51/23/51/23/51/23/51/23/51/2
Branched
dorsal n
rays 71/271/26–71/271/271/271/271/271/271/271/271/27–81/2
Pectoral n
rays 9 10–11 9 9 9 9 8 9 7–8 9 9 9–10
Pelvic n
rays 7 7 6–7 7 7 7 7 7 7 7 7 7
Caudal n
rays /9 + 8/ /8 + 8/ /9 + 8/ /8 + 8/ /8 + 8/ /8 + 8/ /8 + 7/ /9 + 8/ /6–7 + 6–8/ /9 + 8?/ /8–9 + 7–8/ /9 + 7–8/
Lateral line
pores 6–26 24–50 15–25 10–18 23–24 18–31 12–18 14–22 7–12 - 9–15 18–30
Supraorb.
pores 7 6 5 6 6 6 6 6 6 6 5 6–8
Infraorb.
pores 4 + 9 4 + 11 4 + 10 4 + 9 4 + 9 4 + 9 4 + 8–9 4 + 9 4 + 8 4 + 11 4 + 10 4 + 8–11
Supratem.
pores 3 3 3 3 3 3 3 3 4 3 3 3
Preoper-
culo
-mandib.
pores
9 9 9 9 8 9 9 9 9 9 9 7–10
Black dots
on lower
lip Present Var iabl e Va r iab l e Present Present Present Present Present Present ? Present Present
Black bar
on caudal-
n base Light, thin Absent Dark, thick Dark, thick Dark, thick Dark, thick Dark, thick Incomplete Dark, thick Dark, thick Dark, thick Dark, thick
Black dot
on base of
dorsal n Present Absent Present Present Present Absent Present Present Present ? Present Present
Black
stripes on
dorsal n Absent Present Absent Absent Absent Present Absent Absent Absent Absent Absent Absent
Position of
anus Middistance
pelvic-anal Middistance
pelvic-anal Closer to
pelvic n Closer to
anal n Middistance
pelvic-anal Closer to
pelvic n Closer to pelvic
n Middistance
pelvic-anal Closer to
anal n Clos er to anal
n Closer to
anal n Middistance
pelvic-anal
Length of
lateral line
***
Intermedi-
ate Long Intermedi-
ate Short Intermedi-
ate Intermedi-
ate Short Intermedi-
ate Short Intermediate Short Intermediate
Axillary
pelvic lobe Absent Present Absent Absent Absent Present Absent Absent Absent Present Absent Present
2nd pair of
black dots
on lower
lip
Absent Absent Absent Present Absent Absent Present Absent Absent ? Absent Absent
Black
blotch on
throat Absent Absent Absent Absent Present Absent Absent Absent Absent ? Absent Absent
Content courtesy of Springer Nature, terms of use apply. Rights reserved

8
Vol:.(1234567890)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
Schistura cincticauda (Blyth, 1860) (Fig.4C, Table1)
Diagnosis Schistura cincticauda is distinguished from all other species in the S. cincticauda species group by the
combination of the following character states: axillary pelvic lobe absent; base of unbranched and rst branched
dorsal-n rays with prominent black blotch; complete and broad black bar on base of caudal n; 9 + 8 branched
rays in caudal n, 9 rays in pectoral n; colour pattern consisting of 6–8 regular brown bars and regular yellow
interspaces as wide as bars; anus closer to posterior extremity of pelvic-n base than to anal-n origin; incomplete
lateral line, ending before vertical through origin of dorsal n.
Distribution Known only from Moei River watershed (Salween drainage).
Remarks Schistura cincticauda was originally described from ’Tenasserim Provinces’20, at that time including
Myanmar between 11° and 17°N. Kottelat11 redescribed S. cincticauda and designated a neotype, which xes the
type locality in the Mae Nam Moei watershed, about 30km North of Mae Sot. e Mae Nam Moei makes the
border between ailand and the earlier ’Tenasserim Provinces’ of Myanmar. For confusion with S. aurantiaca,
see above.
Schistura crocotula Plongsesthee, Kottelat & Beamish, 2013 (Fig.4D, Table1)
Diagnosis Schistura crocotula is distinguished from all other species in the S. cincticauda species group by the
combination of the following character states: axillary pelvic lobe absent; base of unbranched and rst branched
dorsal-n rays with prominent black blotch; complete and broad black bar on base of caudal n; 8 + 8 branched
rays in caudal n, 9 rays in pectoral n; colour pattern consists of dark brown bars and prominent regular orange
to red interspaces; anus closer to anal-n origin than to posterior extremity of pelvic-n base; incomplete lateral
line, reaching at most to vertical through middistance between pectoral-n base and origin of dorsal n.
Distribution Observed in Bang Saphan and Pranburi rivers (Prachuap Khiri Khan Province, ailand) and
Lenya River (Tanintharyi Region, Myanmar).
Schistura paucifasciata (Hora, 1929) (Fig.4E, Table1)
Diagnosis Schistura paucifasciata is identied as member of the S. cincticauda group by having an incomplete
lateral line, a small body size (max 54.3mm TL according to Hora17) and an emarginate caudal n. Most likely
related to S. balteata, with which it shares a rare colour pattern (2–4 thin dark bars below dorsal n, body
Figure6. Cladogram based on species tree resulting from multi-species coalescence analyses in *BEAST plus
morphocode of the twelve species currently included into the Schistura cincticauda species group. e position
of S. paucifasciata is putative, since no DNA of this species was available. Characters and their states in the
morphocode are: (A)—number of pectoral-n rays (0 = 9, 1 = 10–11, 2 = 8); (B)—number of branched caudal-n
rays (0 = 9 + 8, 1 = 8 + 8, 2 = 7 + 8, 3 = 8 + 7); (C)—length of lateral line (0 = long [ending behind dorsal n base],
1 = intermediate, 2 = short [ending before middistance from pectoral to pelvic-n base]); (D)—position of anus
(0 = half distance between pelvic to anal n, 1 = closer to pelvic n, 2 = closer to anal n); (E)—black dots on
lower lip (0 = present, 1 = variable); (F)—axillary pelvic lobe (0 = absent, 1 = present); (G)—black bar on base
of caudal n (0 = present, 1 = absent, 2 = irregular); (H)—black blotch posterior of median incision of lower lip
(0 = absent, 1 = present) (I)—second pair of black dots on lower lip (0 = absent, 1 = present); (J)—black dot on
base of dorsal n (0 = present, 1 = absent); (K)—black bars on dorsal n (0 = absent, 1 = present); (L)—bars of
body (0 = bars numerous, broad or grey, 1 = 2 to 4 very thin black contrasting bars in middle of ank, 2 = all bars
fused into plain brown body, 3 = most bars fused leaving few interspaces in middle of ank.
Content courtesy of Springer Nature, terms of use apply. Rights reserved

9
Vol.:(0123456789)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
cream-brown), distinguishing these two species from all other Nemacheilidae. It is distinguished from S. bal-
teata by the absence of saddles on the back and by presence of a broad black bar on caudal-n base. Schistura
paucifasciata is further characterised by the combination of the following character states: axillary pelvic lobe
present; absence of prominent black mark on anterior part of dorsal-n base; complete and broad black bar on
base of caudal n; 10–11 rays in pectoral n; anus closer to anal-n origin than to posterior extremity of pelvic-
n base; incomplete lateral line, ending just before dorsal-n origin.
Distribution Known only from the type locality in the middle Irrawaddy basin, Kyaukme district, north-
western Shan State, Myanmar.
Remarks Schistura paucifasciatahas not been collected again since 191117. Menon21 considered that S. pauci-
fasciata is a synonym of S. cincticauda aer having examined the holotype of S. paucifasciata; he did not examine
material of S. cincticauda. His description of S. cincticauda in fact is that of the holotype of S. paucifasciata.
e BMNH paratype has the lower lip pushed down in a non-natural way and it is impossible to observe the
black marks on the lower lip. In S. balteata, which shares the pattern of a few blackish bars below the dorsal n,
some specimens do not have black marks on the lower lip; possibly, their apparent absence in the only available
specimen of S. paucifasciata has no signicance and at this stage should not be retained as diagnostic for the
species. e holotype and paratypes housed by the Zoological Survey of India could not be investigated.
Having three black bars below the dorsal n on an otherwise uniformly brown body is a character shared
with S. balteata. e bars are more widely spaced in S. paucifasciata than in S. balteata. e colour pattern of
juvenile S. paucifasciata, as illustrated by Hora17 has some similarities with that of S. aurantiaca, with 8 grey
bars separated by whitish narrow interspaces. With increasing size, the bars fade away, the body becomes uni-
form reddish brown. At the same time, 3 or 4 narrows bars appear in the interspaces below the dorsal n. Hora
described them as deep reddish brown.
Schistura robertsi Kottelat, 1990 (Fig.4F, Table1)
Diagnosis Schistura robertsi is distinguished from all other species in the S. cincticauda species group by the
combination of the following character states: axillary pelvic lobe absent; base of unbranched and rst branched
dorsal-n rays with prominent black blotch; complete and broad black bar on base of caudal n; 6–7 + 7–8
branched rays in caudal n; 7–8 rays in pectoral n; colour pattern consisting of 1–13 regular brown bars and
1–12 regular yellow interspaces as wide as bars; number of bars and their width very variable between and also
within populations; anus closer to anal-n origin than to posterior extremity of pelvic-n base; incomplete lateral
line, reaching at most to vertical through halfway between pectoral-n base and origin of dorsal n.
Distribution Widely distributed in most drainages of the Andaman Sea slope of ailand, from the Isthmus
of Kra southwards to Phuket Island. It was also found in some localities east of the Tenasserim Range in the upper
Figure7. Detailed geographic origin of samples of the southernmost species of the Schistura cincticauda
species group.
Content courtesy of Springer Nature, terms of use apply. Rights reserved

10
Vol:.(1234567890)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
Khlong Sok and upper Tapi River, which drain to the Gulf of ailand, 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.
Remarks Kottelat11 considered S. robertsi to occur on the Malay Peninsula from Ranong to Songkhla. Mean-
while genetic data have demonstrated that S. robertsi sensu Kottelat11 consists of two lineages, one in the Anda-
man Sea drainage from Phang Nga to Ranong provinces (ailand) and one from Phang Nga and Surat ani
provinces in the north to northern Malaysia in the south, including Langkawi Islands (Fig.1). Kottelat’s original
description of S. robertsi was mostly based on paratypes now identied as S. peninsulae. e n-ray counts of
the holotype were not mentioned separately and the diagnosis is misleading. e holotype was re-examined for
the present study. It has 7 + 7 branched caudal-n rays, 8 and 7 pectoral-n rays (right and le, respectively).
e holotype of S. robertsi has all the characters here considered diagnostic for the northern species and the type
locality is within that range. Schistura robertsi is unique among the species of the S. cincticauda species group by
having oen fewer branched rays in the upper lobe (6–7) of the caudal n than in the lower lobe (7–8).
Schistura tenebrosa Kangrang, Page, Beamish, 2012 (Fig.4G, Table1)
Diagnosis Schistura tenebrosa is distinguished from all other species in the S. cincticauda species group by the
combination of the following character states: body plain brown without any marks; axillary pelvic lobe present;
base of unbranched and rst branched dorsal-n rays with prominent black blotch; presence of black bar on base
of caudal n; 9 + 8 branched rays in caudal n, 9–10 rays in pectoral n; anus midway between posterior extremity
of pelvic-n base and anal-n origin; lateral line incomplete, ending just before vertical through dorsal-n origin.
Distribution Known only from two small streams draining into Vajiralongkorn reservoir, Mae Kwai Noi,
Mae Khlong drainage, Kanchanaburi province, ailand.
Remarks Material of this species was not observed personally, the data were obtained from the original
description and from personal communication with the second author of the original description. e general
body shape of the type material of S. tenebrosa was very similar to the species of the S. cincticauda group. A photo
of the mouth of the holotype shows the presence of prominent black marks in the lower lip as diagnostic for the
Table 2. Morphometric values of Schistura ataranensis, S. hartli, S. myaekanbawensis, S. kuehnei and S.
peninsulae.
S. ataranensis S. hartli S. myaekanbawensis S. kuehnei S. peninsulae
Holotype Range Holotype Paratype Holotype Range Holotype Range Holotype Range
Standard length 43.8 36.0–43.8 36.6 41.0 29.8 23.2–29.8 37.1 31.6–37.1 36.8 32.4–39.4
In percent of standard length
Total length 121.5 119.5–127.8 123.2 123.5 125.5 124.4–126.3 125.1 123.6–125.1 124.5 122.9–128.0
Dorsal head length 17.4 17.4–23.7 20.5 19.1 18.1 18.1–21.1 22.9 22.2–23.3 19.0 18.6–21.6
Lateral head length 20.1 20.1–25.1 23.2 21.3 21.8 21.8–25.0 24.5 23.7–26.1 22.8 22.0–24.8
Predorsal length 52.3 52.2–57.3 52.7 55.7 54.7 54.7–56.9 56.1 54.4–57.5 56.0 54.5–57.0
Pre-pelvic length 53.0 53.0–58.0 53.7 51.1 53.0 52.3–54.3 54.4 53.2–55.1 49.7 49.6–55.1
Pre-anus length 65.5 65.5–68.1 69.8 63.7 64.8 64.8–65.4 67.7 67.0–69.7 70.4 67.3–71.0
Preanal length 79.5 76.7–82.3 81.0 77.3 78.5 78.5–81.0 78.7 77.8–81.2 78.0 76.1–79.8
Head depth at eye 11.0 10.9–13.3 10.5 9.8 9.1 9.1–10.8 12.7 12.7–13.8 10.6 10.1–14.2
Head depth at nape 14.6 12.8–14.8 13.2 12.8 11.4 11.4–13.4 13.5 13.5–14.9 13.0 12.7–16.0
Body depth 14.8 14.8–17.1 17.6 14.8 13.8 13.8–15.8 16.2 16.2–17.1 17.7 14.9–21.0
Depth of caudal peduncle 12.1 12.1–15.6 13.2 12.8 13.1 13.1–15.1 13.7 13.7–14.9 15.2 11.8–15.2
Length of caudal peduncle 11.9 11.6–16.0 12.0 13.7 16.1 15.9–18.1 13.7 13.7–15.5 14.4 14.4–18.4
Snout length 8.9 8.9–15.3 9.5 9.3 12.1 11.6–12.9 15.1 15.1–15.8 9.0 9.0–11.3
Head width at nares 10.3 10.3–13.1 11.0 10.4 10.4 9.8–11.5 15.6 14.5–15.6 11.7 10.7–16.5
Maximum head width 14.6 14.6–18.0 16.1 15.8 14.1 14.1–15.9 18.9 18.9–19.4 17.1 15.6–19.3
Body width at dorsal-n origin 14.8 10.9–14.8 11.2 10.7 10.7 10.7–12.2 13.5 13.5–14.6 13.9 11.3–17.0
Body width at anal-n origin 8.9 6.5–9.3 6.3 6.3 7.7 7.3–8.2 11.1 9.8–11.1 9.8 8.2–10.9
Eye diameter 4.8 4.1–5.5 2.9 3.3 3.0 3.0–3.4 4.3 4.3–4.7 3.3 3.1–4.2
Interorbital distance 5.9 5.9–7.8 6.6 6.6 7.4 6.9–7.5 8.4 8.0–8.4 9.2 6.5–9.2
Length of upper caudal lobe 20.5 20.2–22.9 22.7 23.0 21.5 21.5–23.7 22.6 20.9–22.6 0.0 20.5–23.5
Length of lower caudal lobe 20.5 19.7–21.8 22.0 22.1 20.5 19.4–22.8 21.8 20.6–21.8 22.0 19.4–22.5
Length of medium caudal rays 16.2 16.2–18.1 19.8 20.8 17.8 15.8–19.4 20.2 18.9–20.2 20.1 17.7–20.8
Depth of anal n 15.8 15.8–18.8 18.5 18.6 17.1 15.6–17.7 18.1 18.1–18.6 17.7 15.7–19.7
Length of pelvic n 15.3 15.3–19.3 15.9 18.0 17.4 16.9–19.0 17.3 17.3–18.7 17.9 17.0–19.4
Length of pectoral n 18.0 18.0–22.0 19.0 21.3 19.5 19.5–20.3 17.5 17.5–19.7 17.4 17.5–20.3
In percent of dorsal head length
Snout length 51 51–68 46 49 67 55–68 66 66–71 47 47–59
Eye diameter 27 20–28 14 17 17 16–17 19 19–21 17 15–20
Interorbital distance 34 30–37 32 34 41 33–41 37 34–37 49 32–49
Content courtesy of Springer Nature, terms of use apply. Rights reserved

11
Vol.:(0123456789)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
S. cincticauda species group. Cytochrome b data indicate S. tenebrosa as member of the S. cincticauda species
group (position indicated in Fig.1).
Schistura ataranensis, new species (Fig.5A, Tables1 and 2; Supplementary Material Figs.S1, S2)
Holotype ZRC 61579, 43.8mm SL; Myanmar: Kayin Province: upper Ataran basin (Andaman Sea basin), col-
lected for ornamental sh trade, no details. Paratypes IAPG A11005, 1, 35.6mm SL; ZRC 61580, 1, 41.5mm
SL; CMK 28809, 2, 37.0–41.0mm SL; collected with holotype.
Diagnosis Schistura ataranensis is distinguished from all other species in the S. cincticauda species group by
having 2–3 black stripes on the dorsal n. e following combination of character also distinguishes the species:
absence of a prominent black mark on the anterior part of dorsal-n base; axillary pelvic lobe present; complete
and broad black bar at base of caudal n; 8 + 8 branched rays in caudal n, 9 rays in pectoral n; colour pattern
always includes two prominent regular paler interspaces (orange to pink in life), one below dorsal-n origin,
one before; 1–2 additional, irregular small interspaces on back in front of dorsal and up to 4 irregular yellow to
orange interspaces between dorsal- and caudal-n bases; anus closer to posterior extremity of pelvic-n base
than to anal-n origin; lateral line incomplete, ending under anterior half of dorsal-n base.
Colour pattern In preserved specimens, body (except belly) variable, but mainly plain brown, with a few
vertically elongated pale marks (plain brown areas in fact homologous to fused bars in other species; pale marks
homologous to interspaces). Two light interspaces, one below dorsal-n base and the other in front of dorsal-n
origin, orange to pink in life (light yellow aer xation), continuous with their contralaterals across back. Bar
at base of caudal n broad, black, complete, extending across ventral and dorsal crests, forming a complete ring
around end of caudal peduncle. Dorsal n with 2 or 3 black stripes made of pigments on rays and membranes.
Caudal-n rays (and in most specimen also each pectoral-, pelvic- and anal-n ray) with dark pigment along
whole length of ray. Small dark spots present on each side of median interruption of lower lip. Head entirely
dark brown to dark grey, with black patches around eyes and nostrils, and a dark stripe from front of eyes to
snout. Rostral barbels pigmented, outer one entirely black and inner one with dark base and light tip. Maxillary
barbel unpigmented.
Distribution Known only from the upper Ataran River drainage, in Myanmar.
Etymology Named aer River Ataran, where the type series was collected. An adjective, -is, -is, -e.
Remarks Schistura ataranensis is traded as ornamental sh since at least 2006 under names like ‘Sumo loach’,
‘Sumo loach II’, ‘Schistura cf. balteata’22. However, pictures of shes from the ornamental sh trade suggest that
additional species are confused under these names.
Schistura hartli, new species (Fig.5B, Tables1 and 2; Supplementary Material Figs.S3, S4)
Holotype ZRC 61581, 41.0mm SL; ailand: Surat ani Province: small stream in Khao Sok NP, around 8°57′N
98°36′E; A. Hartl. Paratype CMK 28810, 1, 36.6mm SL; collected with holotype.
Diagnosis Schistura hartli is distinguished from all other species in the S. cincticauda species group by the
combination of the following character states: absence of axillary pelvic lobe; presence of a black patch on throat,
behind median interruption of lower lip; base of unbranched and rst branched dorsal-n rays with prominent
black mark; black bar at base of caudal n; 8 + 8 branched rays in caudal n, 9 rays in pectoral n; ank with
7–10 bars and 8–11 broad pink interspaces; anus more or less midway between posterior extremity of pelvic-n
base and anal-n origin; lateral line incomplete, ending before vertical through dorsal-n origin.
Colour pattern Body with 7–10 broad dark brown bars with broad pink interspaces (turn light yellow aer
xation in formalin or ethanol), all fused with their contralateral on dorsal midline. Bars reaching ventrally to
about level of pectoral-n base. First interspace behind neck yellow in life. Black bar at base of caudal n com-
plete. Dorsal-n with circular to squarish black spot on base of unbranched and anterior 1–2 branched rays.
Dorsal and caudal ns with dark pigments along rays, intensity decreasing with distance from base. Lower lip
with a small dark spot on each side of median interruption; a black patch on throat, behind median interruption
of lower lip. Head dark brown to nearly black, with light brown blotches on gill cover. Maxillary barbel with
small patches of pigments at base. Rostral barbels pigmented, outer one entirely black, inner one with dark base
and light tip.
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 (Fig.5C, Tables1 and 2; Supplementary Material Fig.S5)
Holotype MHNG 2790.081, 29.8mm SL; Myanmar: Tanintharyi Region: Tanintharyi drainage: Kami Chaung,
14°20′52″N 98°31′28″E, 255 masl; M. Kottelat etal., 2 May 2014. Paratypes CMK 24993, 4 (one in ethanol),
22.8–29.4mm SL; collected with holotype.—CMK 24971, 3, 22.7–27.3mm SL; ZRC 64851, 2, 26.6-28.1 mm
SL;Myanmar: Tanintharyi Region: Tanintharyi drainage: Kami Chaung, 14°20′07″N 98°31′04″E, 244 masl; M.
Kottelat etal., 2 May 2014.
Diagnosis Schistura myaekanbawensis is distinguished from all other species in the S. cincticauda species
group by the combination of the following character states: presence of a second black mark on lower lip close
to corner of mouth; an elongate swelling along ventral midline between anus and anal-n origin; absence of
axillary pelvic lobe; base of unbranched and rst branched dorsal-n rays with prominent black blotch; black
bar at base of caudal n; 8 + 7 branched rays in caudal n; 8 rays in pectoral n; anus closer to posterior extrem-
ity of pelvic-n base than to anal-n origin; lateral line incomplete, reaching at most to 2/3 of distance between
pectoral-n base and vertical through dorsal-n origin.
Content courtesy of Springer Nature, terms of use apply. Rights reserved

12
Vol:.(1234567890)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
Colour pattern Body pale brown to yellowish, paler on belly. Flank with 6–12 dark brown bars, separated by
interspaces narrower than bars. Bars meeting contralaterals on dorsal midline. Bars in front of anal n reaching
downwards about to level of pectoral n, those on caudal peduncle reaching contralaterals on ventral midline.
Interspaces between anterior most bars indistinct or only weakly contrasted (more contrasted in smallest speci-
mens). Anterior interspace through neck and posterior margin of opercle to pectoral-n base, thin and incom-
plete. Dark bar at base of caudal n complete and broad, widest on adipose crests. Dorsal-n with triangular
to squarish black spot on base of unbranched and anterior 1–2 branched rays. All ns with dark pigment on
rays, near branching points. A small black spot on each side of median interruption on lower lip (usually poorly
contrasted); another, larger black mark on each corner of mouth (Fig.2). Head dark brown with darker stripe
from snout to eye. Upper lip dark brown, lower one light brown. Maxillary barbel with small patches of black
pigments, outer rostral barbel black, inner rostral barbel with black base and light tip.
Distribution Only known from Kami Chaung, a shallow stream with moderate ow in the upper Tanintharyi
drainage. e individuals were collected in ries, with a substrate of gravel to small stones.
Etymology Named aer the Myaekanbaw region, where the type series was collected. An adjective, -is, -is, -e.
Remarks Schistura myaekanbawensis is unique among the species of the S. cincticauda group by the presence
of a narrow elongated swelling along the vertical midline between the anus and the anal-n origin. Schistura
myaekanbawensis also has bars and interspaces narrower than the other species of this group. e presence of
the swelling maybe seasonal.
Schistura kuehnei, new species (Fig.5D, Tables1 and 2; Supplementary Material Figs.S6, S7)
Holotype ZRC 61582, 37.1mm SL; ailand: Surat ani Province: Tapi River drainage: Khlong Sok watershed:
small forest stream shortly before entering Khlong Sok, about 854′48″N 98°31′30″E; J. Kuehne. Paratypes ZRC
61583, 1, 31.6mm SL; CMK 28811, 2, 33.9–35.6mm SL; collected with holotype.
Diagnosis Schistura kuehnei is distinguished from all other species in the S. cincticauda species group by
the combination of the following character states: absence of axillary pelvic lobe; base of unbranched and rst
branched dorsal-n rays with prominent black blotch; incomplete black bar at base of caudal n; 9 + 8 branched
rays in caudal n, 9 rays in pectoral n; dark brown body with 7–10 bars and narrow pink interspaces; bars
fused in posterior third of body, without pale interspaces; anus about midway between posterior extremity of
pelvic-n base and anal-n origin; lateral line incomplete, reaching at most to vertical through dorsal-n origin.
Colour pattern Body pale brown, paler on belly, with 7–10 broad brown bars separated by thinner pink
interspaces (light yellow aer xation). Bars and interspaces sometimes continuous with contralaterals across
back. In some specimens, interspaces just before and below dorsal-n base broader than others. Bars and inter-
spaces more sharply contrasted between head and dorsal n; from there gradually less contrasted, then body
uniformly brown from anal-n origin. Dorsal-n with triangular to circular black spot on base of unbranched
and anterior 1–2 branched rays. Rays of dorsal and caudal n covered by dark pigments along whole length,
denser and somewhat extending on membranes near rst branching points of rays. Dark bar at caudal n base
incomplete, thin and with a small interruption at upper third, not reaching dorsal and ventral crest. A prominent
and large black mark on each side of median interruption on lower lip, stretching over one third of length of
lower lip. Head dark brown, with dark stripe from front of eyes to snout, small dark patches between eyes and
nostrils; nostril ap dark; interorbital space, tip of snout and sides of head light brown. Maxillary barbel without
pigments. Outer rostral barbel completely black, inner one with dark base and light tip.
Distribution Known only from a small forest stream draining from Khao Sok NP into stream Khlong Sok
(River Tapi drainage) in Surat ani province (Fig.7); at the type locality it co-occurs with S. robertsi.
Etymology Named aer Jens Kühne, in acknowledgement of his long-time support of our ichthyological
work in Southeast Asia. Noun in genitive, indeclinable.
Schistura peninsulae, new species (Fig.5E, Tables1 and 2; Supplementary Material Fig.S8)
Holotype ZRC 61584, 35.6mm SL; Malaysia: Kedah province: Langkawi Island: waterfall below seven wells
(Sungai Borau drainage), 6°23′N 99°40′E. Paratypes CMK 29091, 1, 38.2mm SL; collected with holotype.—ZRC
61585, 5, 32.5–38.4mm SL; ailand: Nakhon Si ammarat Province: Amphoe Chang Klang: Tapi drainage:
waterfall ’Khao Mhen’ 8°18′N 99°39′E. J. Kühne.
Diagnosis Schistura peninsulae is distinguished from all other species in the S. cincticauda species group by
the combination of the following character states: absence of axillary pelvic lobe; base of unbranched and rst
branched dorsal-n rays with prominent black blotch; black bar at base of caudal n; 8–9 + 7-8branched raysin
caudal n; 9–10 rays in pectoral n; anus closer to anal-n origin than to posterior extremity of pelvic-n base;
lateral line incomplete, reaching at most to vertical through halfway between pectoral-n base and origin of
dorsal n.
Colour pattern Body background yellowish to pale brown, with 2–10 dark brown bars separated by inter-
spaces narrower than bars. Width, number and shape of bars variable; some bars branched near inferior extrem-
ity. Bars and interspaces usually sharply contrasted, but in some specimens bars and interspaces not contrasted
and body uniform brown, with only two interspaces remaining, one behind neck and one in front of caudal-n
base. First interspace directly behind neck, reaching ventrally to belly, more contrasted than other interspaces.
Black bar at base of caudal n complete and wide. Dorsal n with a black mark on base of unbranched and rst
two branched dorsal-n rays. On dorsal and caudal ns, dark pigments along each ray. A prominent and large
black mark on each side of median interruption of lower lip, stretching over one third of length of lip. Top and
sides of head dark brown, ventral side light yellow. A black stripe between eyes and snout, nasal tube dark brown,
interorbital space and tip of snout light brown. Maxillary barbel with small patches of black pigments; outer
rostral barbel black; inner rostral barbel with dark base and light tip.
Content courtesy of Springer Nature, terms of use apply. Rights reserved

13
Vol.:(0123456789)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
Distribution Widely distributed on the Malay Peninsula, from Phang Nga (ailand) to Langkawi (Malaysia)
on the west slope and from northern Surat ani province to Phatthalung province (ailand) on the east slope
(Fig.7). Schistura peninsulae occurs in syntopy with S. robertsi in at least one locality in the uppermost Tapi
river basin, in a small stream in the Phang Nga river basin and potentially in some localities on Phuket Island
(see Remarks, below).
Etymology Named aer 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.
Remarks Schistura peninsulae and S. robertsi have similar body shape and colour pattern. e clear genetic
distance and the case of syntopy without hybridisation in the upper River Tapi basin show that they are distinct
evolutionary units. e only external characters that allow to distinguish them are the numbers of rays in pec-
toral n (9–10 in S. peninsulae vs 7–8 in S. robertsi) and branched rays in caudal n (8–9 + 7–8 in S. peninsulae
vs 6–7 + 7–8 in S. robertsi).
e identity of the specimens on Phuket Island is not yet clear. It is possible that S. robertsi and S. peninsulae
co-occur, or that only S. robertsi is present, but with a wider range in the number of branched caudal-n rays. e
only specimen from Phuket that was analysed genetically was identied as S. robertsi in nuclear and mitochon-
drial genes as well as by morphology (8 pectoral-n rays, 7 + 8 branched caudal-n rays). All 20 formalin-xed
specimens from 4 Phuket lots housed in ZRC (ZRC 43693, ZRC 45718, ZRC 49182, ZRC 60821) have 8 pectoral-
n rays (diagnostic for S. robertsi), but 8 specimens have 7 + 7 or 7 + 8 branched caudal-n rays (diagnostic for
S. robertsi), while 12 specimens have 8 + 8 branched caudal-n rays (diagnostic for S. peninsulae). In 8 paratypes
of S. robertsi from Phuket (MCZ 49164) examined in 198811, 4 have 7 + 8 branched caudal-n rays (diagnostic
for S. robertsi) and 4 have 8 + 8 (diagnostic for S. peninsulae).
Key to species of the S. cincticauda species group
1. - Axillary pelvic lobe present. ............................................................................................................................... 2
- No axillary pelvic lobe. ................................................................................................................................... 5
2. - Colour pattern consisting of 2–4 thin dark bars below dorsal n. ................................................................ 3
- Other colour pattern. ...................................................................................................................................... 4
3. - No black bar at base of caudal n; 3–5 black saddles on back; 8 + 8 branched caudal-n rays. ....................
.....................................................................................................................................................................S. balteata
- A black bar at base of caudal n; no dorsal saddles; 9+8 branched caudal-n rays. ..................................
............................................................................................................................................................ S. paucifasciata
4. - Dorsal n with 2–3 black stripes; 8 + 8 branched caudal-n rays; no black mark on anterior part of dorsal-
n base ................................................................................................................................................. S. ataranensis
- Dorsal n with a single row of spots or plain; 9+8 branched caudal-n rays; a prominent black mark on
anterior part of dorsal-n base ............................................................................................................S. tenebrosa
5. - Anus closer to pelvic-n base than to anal-n origin. .................................................................................... 6
- Anus closer to anal-n origin than to pelvic-n base, or at equal distance. ............................................ 7
6. - 8 pectoral-n rays; 8 + 7 branched caudal-n rays; a second pair of black dots on lower lip close to corners
of mouth. ................................................................................................................................. S. myaekanbawensis
- 9-11 pectoral-n rays; 9+8 branched caudal-n rays; a single pair of black dots on lower lip .................
............................................................................................................................................................... S. cincticauda
7. - Anus at equal distance between pelvic-n base and anal-n origin. ............................................................. 8
- Anus closer to anal-n origin than to pelvic-n base. ................................................................................ 9
8. - 8 + 8 branched caudal-n rays; black bar at caudal-n base regular (without interruption); a black patch
on throat, posteriorly of median interruption of lower lip .................................................................... S. hartli
- 9+8 branched caudal-n rays; black bar at base of caudal-n irregular (with interruption); no black
patch on throat ..........................................................................................................................................S. kuehnei
9. - 6–7 branched rays in upper caudal-n lobe; 7–8 rays in pectoral n. ........................................... S. robertsi
- 8-9 branched rays in upper caudal-n lobe; 9-11 rays in pectoral n. ................................................... 10
10. - Brown bars with yellowish interspaces in live specimens; all interspaces very narrow (at most 1/3 of width
of bars) and all of similar width. ....................................................................................................... S. peninsulae
- Brown bars with orange to red interspaces on live specimens; interspaces wider than 1/2 of width of
bars; interspaces under dorsal n wider. ............................................................................................................ 11
11. - 8 + 8 branched caudal-n rays; lateral line reaching at most halfway between pectoral-n base and dorsal
n origin; coastal streams in Prachuap Khiri Khan Province, southern ailand. ....................... S. crocotula
- 9+8 branched caudal-n rays; lateral line reaching vertical through dorsal-n origin; head waters of
Mae Klong, Ataran and Moei rivers. ................................................................................................ S. aurantiaca
Data availability
Details on morphological data are given in the Supplementary Material and on request from the authors.
Sequence data are available from GenBank (Accession numbers: MK886860-MK887044). Specimens housed in
public collections and CMK can be investigated according to the collection’s regulations.
Content courtesy of Springer Nature, terms of use apply. Rights reserved

14
Vol:.(1234567890)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
Received: 15 May 2023; Accepted: 15 September 2023
References
1. Dvořák, T., Bohlen, J., Kottelat, M. & Šlechtová, V. Paracanthocobitis epimekes, a new species from Myanmar and ailand
(Nemacheilidae, Cypriniformes). Ichthyol. Explor. Freshw. IEF-1174, 1–11. https:// doi. org/ 10. 23788/ IEF- 1174 (2022).
2. Kottelat, M. Conspectus Cobitidum: An inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei). Raes Bull.
Zool. 26, 1–199 (2012).
3. Bohlen, J., Petrtýl, M., Chaloupková, P. & Borin, C. Schistura kampucheensis, a new species of loach from Cambodia (Teleostei:
Nemacheilidae). Ichthyol. Explor. Freshw. 26, 353–362 (2016).
4. Kottelat, M. Schistura systomos, a new species of loach from southern Laos (Teleostei: Nemacheilidae). Ichthyol. Explor. Freshw.
28, 9–16 (2017).
5. Kottelat, M. Schistura titan, a new species of loach from Dakchung Plateau, southern Laos (Teleostei: Nemacheilidae). Ichthyol.
Explor. Freshw. 28, 65–73 (2017).
6. Kottelat, M. Mustura celata, a new genus and species of loaches from northern Myanmar, and an overview of Physoschistura and
related taxa (Teleostei: Nemacheilidae). Ichthyol. Explor. Freshw. 28, 289–314 (2018).
7. Kottelat, M. Schistura indawgyiana, a new loach from Lake Indawgyi basin, Myanmar (Teleostei: Nemacheilidae). Ichthyol. Explor.
Freshw. 28, 1–8 (2018).
8. Hosoya, K., Ito, T. & Miyazaki, J.-I. Lefua torrentis, a new species of loach from western Japan (Teleostei: Nemacheilidae). Ichthyol.
Explor. Freshw. 28, 193–201 (2018).
9. Shangningam, B., Kosygin, L., Sinha, B. & Gurumayum, S. D. Aborichthys kailashi and A. pangensis (Cypriniformes: Nemacheili-
dae), two new species from Arunachal Pradesh, India. Ichthyol. Explor. Freshw. 29, 361–370 (2020).
10. Kottelat, M. e shes of inland waters of Southeast Asia: A catalogue and core bibliography of the shes known to occur in
freshwaters, mangroves and estuaries. Raes Bull. Zool. Supplement 27, 1–663 (2013).
11. Kottelat, M. Indochinese nemacheilines. A revision of nemacheiline loaches (Pisces: Cypriniformes) of ailand, Burma, Laos,
Cambodia and southern Viet Nam. (Pfeil, München, 1990).
12. Freyhof, J., Geiger, M. F., Golzarianpour, K. & Patimar, R. Sasanidus, a new generic name for Noemacheilus kermanshahensis
Bănărescu & Nalbant, with discussion of Ilamnemacheilus and Schistura (Teleostei; Nemacheilidae). Zootaxa 4107, 65–80. https://
doi. org/ 10. 11646/ Zoota xa. 4107.1.3 (2016).
13. Sember, A. et al. Karyotype dierentiation in 19 species of river loach shes (Nemacheilidae, Teleostei): extensive variability
associated with rDNA and heterochromatin distribution and its phylogenetic and ecological interpretation. BMC Evol. Biol. 15,
251. https:// doi. org/ 10. 1186/ s12862- 015- 0532-9 (2015).
14. Sgouros, K. et al. A revised molecular phylogeny reveals polyphyly in Schistura (Teleostei: Cypriniformes: Nemacheilidae). Zootaxa
4559, 349 (2019).
15. Bohlen, J., Dvořák, T., Šlechta, V. & Šlechtová, V. Resolving an unnoticed diversity within the Schistura robertsi species complex
(Teleostei: Nemacheilidae) using molecules and morphology. Mol. Phylogen. Evol. 151, 106894. https:// doi. org/ 10. 1016/j. ympev.
2020. 106894 (2020).
16. Dvořák, T., Šlechtová, V. & Bohlen, J. Using species groups to approach the large and taxonomically unresolved freshwater sh
family Nemacheilidae (Teleostei: Cypriniformes). Biology 11, 175. https:// doi. org/ 10. 3390/ biolo gy110 20175 (2022).
17. Hora, S. L. Notes on Fishes in the Indian Museum-Loaches of the Genus Nemachilus from Burma. Rec. Indian Mus. 31, 311–334
(1929).
18. Plongsesthee, R., Page, L. M. & Beamish, F. W. H. Schistura aurantiaca, a new species from the Mae Khlong basin, ailand (Tel-
eostei: Nemacheilidae). Ichthyol. Explor. Freshwaters 22, 169–178 (2011).
19. Rendahl, H. Die Süsswassersche Birmas – I. Die Familie Cobitidae. Arkiv Zool. 40, 1–116 (1948).
20. Blyth, E. Report on some shes received chiey from the Sitang River and its tributary streams, Tenasserim Provinces. J. Asiat.
Soc. Bengal 29(2), 138–174 (1860).
21. Menon, A. G. K. e fauna of India and the adjacent countries. Pisces IV Teleostei – Cobitidea. Part 1. Homalopteridae. (Zoological
Survey of India, Calcutta, 1987).
22. Ford, M. (ed). SeriouslyFish. https:// www. serio usly sh. com. (3 July 2023).
Acknowledgements
We are thankful to J. Freyhof, A. Hartl, K. Kubota, J. Kühne, K. Lim, I. Seidel, S. Somadee, T.K. Toe, K. Udomrit-
thirujand T. Win for help in obtaining specimens, to K.K.P. Lim (ZRC) for access to material under his care,to
M. Petrtýl for help with photographing the preserved material and for preparing X-rays, to A. Hartl and J. Kühne
for pictures of live specimens, to M. Sorce (MCZ) for photographs of paratypes of S. robertsi, to James Maclaine
(BMNH) for the picture of the mouth of S. paucifasciata and to Larry Page (UF) for information on S. tenebrosa.
BMNH and UF made pictures of the types of S. paucifasciata and S. tenebrosa. e study received nancial
support from grants 206/08/0637 and 19-18453S of the Grant Agency of the Czech Republic. MK worked in
Myanmar with Fauna & Flora International (FFI), as part of the Tanintharyi Conservation Programme, with
the nancial assistance of the European Union, Helmsley Charitable Trust, Segre Foundation, the Lighthouse
Foundation and the Arcadia Fund. Nature and Wildlife Conservation Division, Myanmar Forest Department,
gave permission to survey the Tanintharyi River. anks also go to the participants in the survey, Zau Lunn,
Nyein Chan (Fauna & Flora International), L. K. C. Yun (Nature and Wildlife Conservation Division, Forest
Department), Moe Moe War, Kyaw Htay Aung (Dawei Research Association), Aung an Hlaing, Yin Htwe
and Saw Kwar Lar (from Myaekanbaw village); U Tun Phyu and his family provided help and hospitality in
Myaekanbaw village.
Author contributions
TD did most data analysis and wrote the rst dra of the manuscript, JB and VŠ designed the study and improved
the manuscript, MK improved the manuscript. All authors discussed the results.
Competing interests
e authors declare no competing interests.
Content courtesy of Springer Nature, terms of use apply. Rights reserved

15
Vol.:(0123456789)
Scientic Reports | (2023) 13:16996 | https://doi.org/10.1038/s41598-023-42852-1
www.nature.com/scientificreports/
Additional information
Supplementary Information e online version contains supplementary material available at https:// doi. org/
10. 1038/ s41598- 023- 42852-1.
Correspondence and requests for materials should be addressed to J.B.
Reprints and permissions information is available at www.nature.com/reprints.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and
institutional aliations.
Open Access is article is licensed under a Creative Commons Attribution 4.0 International
License, which permits use, sharing, adaptation, distribution and reproduction in any medium or
format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the
Creative Commons licence, and indicate if changes were made. e images or other third party material in this
article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the
material. If material is not included in the article’s Creative Commons licence and your intended use is not
permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from
the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/.
© e Author(s) 2023
Content courtesy of Springer Nature, terms of use apply. Rights reserved

1.
2.
3.
4.
5.
6.
Terms and Conditions
Springer Nature journal content, brought to you courtesy of Springer Nature Customer Service Center GmbH (“Springer Nature”).
Springer Nature supports a reasonable amount of sharing of research papers by authors, subscribers and authorised users (“Users”), for small-
scale personal, non-commercial use provided that all copyright, trade and service marks and other proprietary notices are maintained. By
accessing, sharing, receiving or otherwise using the Springer Nature journal content you agree to these terms of use (“Terms”). For these
purposes, Springer Nature considers academic use (by researchers and students) to be non-commercial.
These Terms are supplementary and will apply in addition to any applicable website terms and conditions, a relevant site licence or a personal
subscription. These Terms will prevail over any conflict or ambiguity with regards to the relevant terms, a site licence or a personal subscription
(to the extent of the conflict or ambiguity only). For Creative Commons-licensed articles, the terms of the Creative Commons license used will
apply.
We collect and use personal data to provide access to the Springer Nature journal content. We may also use these personal data internally within
ResearchGate and Springer Nature and as agreed share it, in an anonymised way, for purposes of tracking, analysis and reporting. We will not
otherwise disclose your personal data outside the ResearchGate or the Springer Nature group of companies unless we have your permission as
detailed in the Privacy Policy.
While Users may use the Springer Nature journal content for small scale, personal non-commercial use, it is important to note that Users may
not:
use such content for the purpose of providing other users with access on a regular or large scale basis or as a means to circumvent access
control;
use such content where to do so would be considered a criminal or statutory offence in any jurisdiction, or gives rise to civil liability, or is
otherwise unlawful;
falsely or misleadingly imply or suggest endorsement, approval , sponsorship, or association unless explicitly agreed to by Springer Nature in
writing;
use bots or other automated methods to access the content or redirect messages
override any security feature or exclusionary protocol; or
share the content in order to create substitute for Springer Nature products or services or a systematic database of Springer Nature journal
content.
In line with the restriction against commercial use, Springer Nature does not permit the creation of a product or service that creates revenue,
royalties, rent or income from our content or its inclusion as part of a paid for service or for other commercial gain. Springer Nature journal
content cannot be used for inter-library loans and librarians may not upload Springer Nature journal content on a large scale into their, or any
other, institutional repository.
These terms of use are reviewed regularly and may be amended at any time. Springer Nature is not obligated to publish any information or
content on this website and may remove it or features or functionality at our sole discretion, at any time with or without notice. Springer Nature
may revoke this licence to you at any time and remove access to any copies of the Springer Nature journal content which have been saved.
To the fullest extent permitted by law, Springer Nature makes no warranties, representations or guarantees to Users, either express or implied
with respect to the Springer nature journal content and all parties disclaim and waive any implied warranties or warranties imposed by law,
including merchantability or fitness for any particular purpose.
Please note that these rights do not automatically extend to content, data or other material published by Springer Nature that may be licensed
from third parties.
If you would like to use or distribute our Springer Nature journal content to a wider audience or on a regular basis or in any other manner not
expressly permitted by these Terms, please contact Springer Nature at
onlineservice@springernature.com