The plankton samples collected from the Subansiri floodplain wetlands revealed a rich Cladocera assemblage of 55 species belonging to 30 genera and 7 families. The species richness represents 42% and 75% of the total amount of fresh water species reported from India and Assam, respectively. Chydoridae was the most speciose family, with 31 species, while Ilyocryptidae was represented by a single species. Sididae, Daphniidae, Bosminidae, Moinidae and Macrothricidae were represented by four, five, three, two and four species, respectively. The faunal composition is represented by cosmopolitan, tropical and oriental elements. The documentation of Diaphanosoma dubium, Latonopsis australis, Simocephalus mixtus, Chydorus sphaericus, Chydorus parvus, Chydorus ovalis, Alonella clathratula, Pleuroxus cf. denticulatus, Picripleuroxus quasidenticulatus, Celsinotum macronyx, Coronatella anodonta and Kurzia (Rostrukurzia) brevilabris has biogeographic importance. We provide brief geographical distributional remarks about these 12 species from the collected samples. This was a preliminary study, as the fauna from the Indian subcontinent is poorly documented, and requires a taxonomic revision as a whole. The faunistic diversity of cladocerans comprises a clear representation of a tropical cladoceran assemblage.
Glyptothorax mibangi, a new sisorid catfish, is described from the Tisa River of Arunachal Pradesh, India. The new species can be distinguished from its congeners in the Ganga-Brahmaputra and Barak-Surma-Meghna basins by the following combination of characters: an obtuse leaf-shaped thoracic adhesive apparatus with a spindle-shaped median depression, skin ridges present over the entire apparatus including the depressed region; ventral surface of pectoral spine and first pelvic-fin ray non-plaited; slender body with depth of 10.4-13.5% SL; caudal peduncle shallow with depth 6.8-8.3% SL; snout long with length 52.9-58.6% HL; and 2+7 gill rakers on the first branchial arch.
The feeding ecology of Pachypterus atherinoides was investigated for two consecutive years (2013-2015) from floodplain wetlands in the Subansiri river basin of Assam, North East India. The analysis of its gut content revealed the presence of 62 genera of planktonic life forms along with other animal matters. The organization of the alimentary tract and maximum Relative Mean Length of Gut (0.511±0.029 mm) indicated its carnivorous food habit. The peak gastro-somatic index (GSI) in winter-spring seasons and summer-rainy seasons indicated alteration of its feeding intensity. Furthermore, higher diet breadth on resource use (Levins’ and Hurlbert’s) with zooplankton compared to phytoplankton and total plankton confirmed its zooplanktivore habit. The feeding strategy plots also suggested greater preference to zooplankton compared to phytoplankton. The organization of its gill rakers specified a secondary modification of gut towards either carnivory or specialized zooplanktivory. So, the fish may be a carni-omnivore with preference to zooplankton.
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