Ecology and biology of aquatic snails and their control: V. Ecology of snails in Deepor Beel wetland, Assam

摘要

Ecology of aquatic snails in a perennial waterlogged area (latitudes 26 deg 05 min and 26 deg 10 min North and longitudes 91 deg 35 min and 91 deg 42 min East) was studied. An analogue map prepared from a single season remotely sensed satellite data and field study revealed 3 types of land cover classes with a predominance 49.30% waterlogged area. Snail ecology was studied at 6 different locations whose central co-ordinates of latitudes and longitudes were marked by a global positioning system (GPS) device, revealed the presence of 10 species of aquatic snails associated with 13 macrophyte species. Population density of the snail species Lymnaea acuminata f. rufescens and Indoplanorbis exustus was high (RF% > 12%) which were associated with a high density of the macrophytes viz., Elodea species, Ceratophyllum demersum and Najas indica. The population density of the snails Bellamya bengalensis f. typical, B. bengalensis, B. dissimilis, Pila theobaldi, L. luteolaf. ovalis and Nymphea stellata, Monocorea species, Lemna Paucicostata, Azolla pinnata, Potamogaton species, Evolvulus species, Eicchornia crassipes and Ipomoea reptans were moderate (RF% > 4%, < 12%). The population density of Gyraulus convexiusculus, Melanoides tuberculata, L. acuminataf. chlamys and the macrophyte Salvania cucullata, Trapa nutans var. bispinosa and Ipomoea reptans were less (RF% <4%). Limnological evidences indicate a variation of low dissolved carbon dioxide (2-6 ppm), high total alkalinity (70-85ppm) and a pH rangeof 7.5-7.7 in the study site ecologically suitable for a diverse snail fauna.