Substratum as a factor in the distribution of two prosobranch freshwater snails, Viviparus bengalensis and Melania scabra

Abstract

Laboratory experiments were conducted to ascertain the substratum preferendum of Viviparus bengalensis and Melania scabra. When the food (Spirogyra) was offered both on stones and sand, the average distribution of V. bengalensis and M. scabra was I9% and io% on stone and 52% and 80% on sand respectively. In the absence of food from both stone and sand and also when sand alone was baited, both snails flocked principally towards sand. When stone alone was provided with food, V. bengalensis and M. scabra displayed 16% and 15% distribution on stone and 49% and 45% on sand respectively. Ecological significance of these results is discussed.one to the other. The pulmonate snail Physa integra prefers hard stony substrate whereas Heliosoma antrosa favours a substratum of sand (Clampitt, 1973). Calow (1974) emphasized the importance of stone texture as a determinant of the dispersal pattern for the pulmonates, Ancylusliaviatilis and Planorbis controtus.Since substratum preferendum of both these two very common prosobranchs has not been investigated, the present probe was undertaken to know whether, V. bengalensis and M. scabra are selective in their substratum.

Life on the edge: survival and behavioural responses of freshwater gill‐breathing snails to declining water level and substratum drying

“…The burrowing behaviour of B. tentaculata and P. antipodarum was independent of substratum drying and shallow, just below the substratum surface. Apart from its antidesiccation role, burrowing may also protect snails against heavy wave actions (Vaidya, 1979), water current (Holomuzki & Biggs, 1999) and excessive fluctuations in temperature (Egonmwan, 2007;Seuffert et al, 2010). Burrowing behaviour is the most common strategy exhibited by gastropods in sandy tidal zones, as sand is a suitable substratum to burrow (Levinton et al, 1995;Vanagt, Vincx & Degraer, 2008).…”

“…Behavioural responses of snails, such as horizontal migrations and burrowing, are a common strategy of avoiding adverse environmental conditions, such as winter ice cover, extreme temperatures or fluctuating water level (Vaidya, 1979;Aldridge, 1983;Pozna nska et al, 2015). Finding a suitable microhabitat can be crucial to surviving periodic water-level fluctuations (Strachan, Chester & Robson, 2014), particularly if the period of desiccation is not long.…”