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Schistura crocotula, a new loach from Peninsular Thailand (Teleostei: Nemacheilidae)
Abstract
Schistura crocotula, a new species, is described from Khanan River, Prachuap Khiri Khan Province, southern Thailand. It is distinguished from other species of Schistura in Southeast Asia by a depressed head; 6-11 dark brown bars against an orange background; the first bar is the widest, two bars are under dorsal fin; interspaces are often indistinct on posterior part of body; a thick black bar at the base of the caudal fin.
... However, several monophyletic species groups have been proposed to exist within the genus Schistura. One of these groups of morphologically similar species is the 'Schistura robertsi group', which occurs in eastern Myanmar as well as in western and southern Thailand (Kottelat, 1990;Plongsesthee et al., 2011;Plongsesthee et al., 2013). The species complex in the present understanding contains five described and one undescribed species: 1. S. robertsi Kottelat, 1990, found in southern Thailand until the Langkawi Island in northern Malaysia; 2. S. cincticauda (Blyth, 1860), endemic to the Moei River, a tributary of the Salween River in western Thailand; 3. S. aurantiaca Plongsesthee et al., 2011, known from tributaries of the upper Khwae Noi in Mae Klong basin; 4. S. balteata (Rendahl, 1948), from the historical Tenasserim region in southeast Myanmar; 5. S. crocotula Plongsesthee et al., 2013, from the Khanan River in Prachuap Kkiri Khan province, Thailand, on the eastern Malay Peninsula; and 6. S. sp 'Sumo', an undescribed species exported for ornamental fish trade from the Ataran River in eastern Myanmar. ...
... One of these groups of morphologically similar species is the 'Schistura robertsi group', which occurs in eastern Myanmar as well as in western and southern Thailand (Kottelat, 1990;Plongsesthee et al., 2011;Plongsesthee et al., 2013). The species complex in the present understanding contains five described and one undescribed species: 1. S. robertsi Kottelat, 1990, found in southern Thailand until the Langkawi Island in northern Malaysia; 2. S. cincticauda (Blyth, 1860), endemic to the Moei River, a tributary of the Salween River in western Thailand; 3. S. aurantiaca Plongsesthee et al., 2011, known from tributaries of the upper Khwae Noi in Mae Klong basin; 4. S. balteata (Rendahl, 1948), from the historical Tenasserim region in southeast Myanmar; 5. S. crocotula Plongsesthee et al., 2013, from the Khanan River in Prachuap Kkiri Khan province, Thailand, on the eastern Malay Peninsula; and 6. S. sp 'Sumo', an undescribed species exported for ornamental fish trade from the Ataran River in eastern Myanmar. Three of these species have been identified comparably recently, and members of the S. robertsi species complex from other regions have not been identified, yet, opening the possibility that more species might be hidden within this group. ...
... Osteological characters were evaluated using micro-X-ray pictures of selected specimens. External morphological characters were selected according to Kottelat (1990) and to former descriptions of species included in the S. robertsi species complex (Plongsesthee et al., 2011;Plongsesthee et al., 2013). Altogether, the analysis included 18 characters from morphometrics, meristics, osteology and pigmentation of 193 specimens. ...
The Schistura robertsi species complex is a group of freshwater fish inhabiting streams in southeast Myanmar as well as in western and southern Thailand. In southern Thailand, the distribution exceeds the biogeographically important ‘Surat Thani – Krabi line’. The complex is believed to include five described and one undescribed species, but monophyly and systematics of the group have never been studied explicitly. The present study aims to resolve the number of species within the Schistura robertsi group as well as their distribution areas and phylogenetic relations. We analysed mitochondrial and nuclear sequence data of 86 specimens from 47 localities and 18 morphological characters of 193 specimens. The phylogenetic analyses revealed the S. robertsi complex to be monophyletic and to be composed of ten major lineages. Six of them correspond to the known described or undescribed species, but another four newly identified clades reveal the existence of an overlooked diversity within the group. All genetic lineages are statistically highly supported and all are morphologically diagnosable, suggesting that they represent distinct species. The distribution areas of several clades overlap, the cases of direct co-occurrence show no sign of hybridisation.
... Balitorid loaches (balitoridae) are widely distributed across Eurasia including in Thailand [13]. However, these species are one of the least studied groups of freshwater fishes, especially in their ecology [14], although they have been studied in regard to husbandry for tropical fish hobbyists. ...
Stream degradation increases with high anthropogenic activity and climate variability, while declines occur in biodiversity. However, few studies have been undertaken on tropical waterways, a major impediment to biodiversity conservation. The present study was conducted on 95 relatively pristine small streams in Eastern Thailand with 10 reasonably uncommon species of balitorid fishes. Measurements were made of 21 physical and chemical factors and the substrate particle size. Stepwise regression identified the direct importance of substrate particle size and nitrate on the species’ richness of balitorids, whereas its abundance was negatively related with iron concentrations. A Canonical Correspondence Analysis identified three fish groups: the 1st group was negatively correlated with ammonia and positively correlated with dissolved silica, the 2nd group was positively correlated with substrate particle size and negatively correlated with stream ambient temperature and ammonia concentration, and the 3rd group was negatively correlated with low dissolved silica, respectively. The results of this study may indicate the vulnerability of balitorids under climate warming and anthropogenic pressure that alter the water physicochemical factors and river degradation including the substrate type. Thus, a conservation framework should be provided regarding the limits for water temperature, ammonia, and iron in Thailand’s Water Quality Criteria to better protect its freshwater ecosystem. Balitorid is a potential bioindicator for evaluating the river temperature effect in combination with ammonia nutrient stressors as long as the way-of-life habits of the species are taken into account.
Fish species were collected by electrofishing from 96 sites, representing 79 species, in lightly exploited rivers in western Thailand. Significant chemical and physical environmental factors associated with species numbers and total fish abundance were identified using multiple linear regression. Total abundance correlated negatively with water depth and temperature (r = 0.4, p < 0.05), whereas species numbers correlated positively with river discharge and negatively with elevation (r = 0.6, p < 0.05). Chemical and physical factors that significantly influenced species distribution were determined using partial least squares regression analysis, (p < 0.05; axes 1, r = 0.8; axes 2, r = 0.85), and included elevation, river discharge, width and depth as well as ambient oxygen, alkalinity and pH. Fish were placed into four categories according to their habitat occupancy and abundance and termed; uncommon (54 species), common (16 species), even (8 species) and uneven (1 species), respectively.
Re-examination of the holotype of Hepsetus odoe indicates that it falls within the range of H. akawo and consequently H. akawo is a junior synonym of H. odoe. As a result, the specimens from the western part of West Africa (from the Senegal to the Cavally River), formerly attributed to H. odoe, remain unnamed. The species is named as H. occidentalis, new species.
Microphilypnus tapajosensis, new species, is described from 48 specimens collected from two sites in Tapajós River. The new species is diagnosed from congeners by the following combination of characters: presence of sexual dichromatism, females with pale yellow color, with scattered, small dark dots, and males yellow, covered with dark brown irregular marks on trunk, head densely covered with black dots, and oblique brown stripes on unpaired fins; head deep; 23-26 lateral scales; cycloid scales on opercle, usually covered with skin.
Pseudolaguvia assula, new species, is described from the Ganges River drainage in Nepal. It differs from all congeners in having the following combination of characters: eye diameter 9-13 % HL, head length 29.4-32.4 % SL, head width 21.7-24.8 % SL, pectoral fin length 27.6-32.5 % SL, pectoral-fin spine length 23.3-28.3 % SL, smooth anterior margin of dorsal-fin spine, 4-6 serrae on posterior margin of dorsal-fin spine, dorsal-fin spine length 20.3-24.8 % SL, body depth at anus 13.7-16.2 % SL, adipose-fin base length 13.1-17.2 % SL, caudal peduncle length 15.4-17.0 % SL, caudal peduncle depth 7.0-8.3 % SL, 28-29 total vertebrae and almost uniformly brown body without distinct pale bands or stripes.
Schistura udomritthiruji, new species, is described from streams draining to the Andaman Sea in southern Thailand between Takua Pa and Ranong. It is distinguished from congeners by the following characters: dark bars on the body much thinner in the anterior half of the body than in the posterior half; 9+8 branched rays in the caudal fin; males with suborbital flap; lateral line ends above base of anal fin; caudal fin hyaline and dark bars on posterior half of body more than twice as wide as interspaces.
A new genus (Laocypris) and 64 new species of fishes are described from Laos. The new species belong to the genera Acrossocheilus (1), Crossocheilus (1), Danio (3), Garra (1), Laocypris (1), Mystacoleucus (1), Poropuntius (4), Puntius (1), Rasbora (2) (Cyprinidae), Hemimyzon (2), Homaloptera (1), Schistura (39), Sectoria (1), Vanmanenia (2) (Balitoridae), Pseudomystus (1) (Bagridae), Doryichthys (1) (Syngn ath id ae), C hauduria (1) (C hau d h u riid ae) and M onotrete (1) (Tetraodontidae). Introduction Fish surveys conducted in Laos between 1996 and 1999 have increased the number of species known in the country from some 210 recorded in the literature as at 1996 to 481 (15 of them not native to the country) recognized in a just-completed field guide (Kottelat, 2000a). Several of the species discovered during these surveys have been described elsewhere (e.g., Britz & Kottelat, 1999a, b; Chen et al., 1999; Chen & Kottelat, 2000; Fang & Kottelat, 1999,2000; Kottelat, 1998; Kottelat & Brehier, 1999; Kottelat & Ng, 1999; Larson & Vidthayanon, 2000; Ng, 1999a-b; Ng & Kottelat, 1998, 1999,2000a-c). The field guide is due to be published in the second quarter of 2000 (a time-frame beyond my control) and clearly, it is desirable that the large number of species still unnamed should be named and identified in this work. It would be counterproductive to omit them from the fieldguide or to list them without valid names. The purpose of the present paper is to make names formally available for them.
Schistura aurantiaca, new species, is described from the Mae Khlong basin in western Thailand. It is distinguished from all other species of Schistura by a unique color pattern of 3-9 orange bars on the side of the body, with the 1st bar immediately behind the head and the 2nd bar near the dorsal-fin origin and widely separated so that most of the nape and the anterior side of the body are uniformly brown. The species reaches only 41 mm SL and in-habits shallow gravel and rubble riffles in small streams.
Total relative abundance of fish and species richness at 95 sites in small rivers varied significantly with physicochemical
factors. Species richness was negatively and positively related with pH and dissolved oxygen, respectively. Relative abundance
varied inversely with discharge and ambient ammonia and, directly with depth, substratum, ambient oxygen and alkalinity. Fish
were represented by 62 species, the most common being Rasbora paviei, Puntius binotatus and Channa gachua. Canonical correspondence analysis related species and their relative abundances with eight environmental variables into four
groups. The most species-rich group was associated with approximately average values for the significant variables. The group
with the fewest species was associated with high oxygen and low ammonia and alkalinity. The other two groups had similar numbers
of species, one being associated with high ammonia and alkalinity and low oxygen. Species in the other group were found at
locations where rivers were relatively wide with comparatively high oxygen and low ammonia concentrations.
Sexually dimorphic characteristics are described for four species of Schistura from the Mae Khlong basin and peninsular Thailand. Males of S. mahnerti have a suborbital flap and rows of unculi on the upper surfaces of the pectoral-fin rays. Females of S. mahnerti have a suborbital groove. None of the morphological measurements differ significantly between males and females of S. mahnerti. In the other three species, S. aurantiaca, S. cf. aurantiaca, and S. sexcauda, all indi-viduals lack the flap or groove, but most males have a conspicuous black botch on the procurrent rays of the upper lobe of the caudal fin, a feature absent in most females. Some morphometric characteristics vary between sexes of these spe-cies. Sexually dimorphic traits presumably have a function related to reproduction; however, little is known about repro-duction in Schistura, and variation in morphology in relation to habitat or other environmental factors has not been studied.