The identity of Clarias batrachus, a species hitherto thought to be widely distributed throughout South and Southeast Asia, is clarified by the designation of a neotype. The neotype designation is necessary because of the ambiguous data in Linnaeus' original description and it fixes the type locality to Java. The variability observed in what is currently recognized as C. batrachus is discussed; morphological and karyological data indicate that four species are confused under the name C. batrachus.

We have recorded 54 species of non-native or alien freshwater fishes from 14 of the 15 reservoirs in Singapore. 31 of these species are established and breeding in the reservoirs. Three species (Mystus wolffii, Amphilophus citrinellum, and Satanoperca jurupari) represent new alien records for Singapore.

Psilorhynchus sucatio (Hamilton) is redescribed based on the examination of 462 specimens, 13-67 mm standard length (SL). Psilorhynchus nudithoracicus Tilak & Husain is redescribed based on the examination of 97 specimens, 10-68 mm SL. Psilorhynchus gracilis Rainboth is placed in the synonymy of P. nudithoracicus. Psilorhynchus hamiltoni, a new species and a member of the P. balitora species group, is described from the Tista River in West Bengal, India. It is distinguished from all other members of the P. balitora species group by having a well-developed lateral stripe, 6-7 poorly developed saddles that do not make contact with the lateral blotches, 7-11 lateral blotches, 34-35 lateral line scales, 9+8-9 principal caudal-fin rays, 36 total vertebrae, and the ventral surface between paired fins with a broad rectangular scaleless patch. A key to the species groups of Psilorhynchus is also provided, as are revised diagnoses for the P. balitora and P. nudithoracicus species groups.

Pareuchiloglanis macropterus new species, is described from the Salween River (Nujiang) and Irrawaddy River drainages in southern China, and P. rhabdurus new species, is described from the Red River (Song Hong) drainage in northern Vietnam. Pareuchiloglanis macropterus can be distinguished from congeners by the following unique combination of characters: prepelvic length 37.0 42.2% SL; length of adipose-fin base 31.8 37.0% SL (dorsal-fin base 3.3 3.5 times in adipose-fin base); caudal peduncle length 17.6 20.0% SL; caudal peduncle depth 6.8 7.4% SL (2.4 3.0 times in caudal peduncle length); body depth at anus 9.5 12.6% SL; snout length 50.3 56.5% HL; interorbital distance 24.6 30.2% HL; 41 42 vertebrae; pectoral fin reaching to pelvic-fin origin; ventral limit of gill opening to level of third or fourth pectoral-fin element; posterior base of adipose fin notched and separate from caudal fin; and presence of pale patches on body. Pareuchiloglanis rhabdurus can be distinguished from congeners chiefly by a slender body (8.7% SL) and caudal peduncle (4.2% SL; 4.2 times in caudal peduncle length), as well as a combination of the following characters: length of adipose-fin base 34.7% SL; dorsal to adipose distance 12.2% SL; caudal peduncle length 17.6% SL; snout length 57.0% HL; interorbital distance 25.5% HL; adipose and caudal fins separate; and ventral limit of gill opening to base of first pectoral-fin element.

Summary 1.Identifying the ecological and life-history correlates of local extinction may elucidate mechanisms by which species traits and the environment interact to result in extinctions, and will help to predict and target extinction-prone species for inclusion in conservation programmes. Freshwater habitats are known to be highly threatened in Southeast Asia but the correlates of extinction among tropical freshwater fish remains unclear. 2. To bridge this knowledge gap, we examined extinction correlates of the freshwater fish of Singapore using machine learning methods: conditional inference trees and forests. Singapore is an ideal study site as it has experienced a high degree of habitat loss and has a well-studied ichthyofauna compared with other countries in the region. 3. The local range of a species was the only significant predictor of extinctions: range-restricted species were more likely to go extinct. 4. Other traits found to be important predictors of extinction risk in temperate regions or hypothesized to predict extinctions based on theory included regional geographic distribution, vertical position, feeding guild, body size, number of congeners, air-breathing capability and habitat preference. These factors did not appear to drive extinctions of freshwater fish in Singapore, although forest-dependent species are more likely to have a restricted local range. 5. Synthesis and applications. Local extinctions of freshwater fish in Singapore are random with respect to ecological and life-history traits because habitat loss is responsible for the removal of entire populations. The fish fauna of Southeast Asia is so poorly known that intensive field surveys are required to identify hotspots of freshwater fish endemism which may be vulnerable to future extinction. These hotspots should then be incorporated into national conservation plans. Where complete habitat protection is not possible, for example, in existing logging concessions and plantations, local authorities should establish partnerships with management companies to ameliorate impacts on fish fauna. Within Singapore, the Nee Soon Swamp Forest is one such hotspot of fish endemism and must be conserved to protect the last populations of five fish species endemic to this location on the island.

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A well-developed second ural half-centrum is a peculiar characteristic of the caudal skeleton of certain siluriforms, not seen in other Recent ostariophysans. Although the character has been previously recorded in the literature, its exact taxonomic distribution, structure, ontogeny, and phylogenetic meaning within siluriforms are not yet determined. In this paper, the degree of development of the second ural half-centrum is surveyed across the order. The ontogeny of the relevant axial structures in the posterior region of the vertebral column is reported in representative siluriform taxa. The condition where the second ural centrum is well formed and forms a complete intervertebral joint anteriorly with the compound caudal centrum is considered derived within siluriforms, a character state homoplastic with the primitive state in more distant teleostean outgroups. Various catfishes display that derived condition, which is informative about relationships at different levels within the group. The most inclusive of those clades is the superfamily Sisoroidea, including the families Amblycipitidae, Akysidae, Sisoridae, Erethistidae, and Aspredinidae. The placement of the neotropical Aspredinidae into an otherwise exclusively Asian clade has important biogeographical implications and the structure of the second ural centrum provides additional support to that hypothesis. Based on the currently available knowledge on the relationships among catfishes, a well-developed second ural centrum is hypothesized to be a result of six different events in siluriforms.

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