Diversity and Distributional Pattern of Aquatic Beetles in Sunderban, West Bengal

Overall aim of this study was to know the diversity of aquatic beetles and their distribution pattern in different islands of Sunderban, West Bengal. Among the eleven orders of aquatic insects the most common ones are aquatic Coleoptera or aquatic beetles. Aquatic beetles are generally involved in nutrient recycling and form an important component of natural food web in aquatic ecosystem. Sometimes they serve as reliable indicators of aquatic system.

A total of 37 species under 5 families of aquatic beetles (Coleoptera) have been recorded from different water bodies of Sajnekhali (22° 07'242'' N and 088° 49'458'' E), Gosaba (22° 09'470'' N and 088° 48'100'' E), Bali (22° 04'324'' N and 088° 42'243'' E) and Satjelia (22° 08'547'' N and 088° 51'664'' E) (Eastern side) and Sagar island (Western side) of Sunderban in West Bengal part. It has been found that the family Dytiscidae was the most abundant group constituting 51% of the total aquatic beetle species reported from Sunderban, West Bengal, followed by Hydrophilidae (27%), Noteridae (11%), Gyrinidae (8%) and Spercheidae (3%). Of them, Canthydrus laetabilis (Walker) of the family Noteridae is the most common species found in all the islands. Globeria leachi Hope of the family Hydrophilidae is found only in Bali island whereas, Helochares lentus Sharp of the family Hydrophilidae and Laccophilus sharpi Regimbart of the family Dytiscidae are only found in Sagar island. Besides this, three species of the family Gyrinidae, namely, Orectochilus (Patrus) haemorrhous Regimbart, Orectochilus (Patrus) ribeiroi Vazirani and Orectochilus (Patrus) similis Ochs and one species of the family of Spercheidae, namely, Spercheus gibbus Champion are only reported from Sajnekhali.