Aspects of The Ecology and Biology of Three Gastropods, Nerita Plicata, N. Undata And N. Textilis (prosobranchia, :eritacea) at The Kenya Coast

Abstract

The studies performed at Nyali and Mkomani rocky shores not only show that all the three species, plicata, undata and textilis make neap-spring tidal migrations but also exhibit season-related migrations. Each species rests at significantly (P<0.001) higher levels around spring days than around neap days. Seasonally each species rests at significantly (P<0.001)higher levels during the SEM (South East Monsoon) than during the NEM North East Monsoon).The mean resting levels of the high level populations of plicata and undata were significantly (P< 0.001)higher than the high water levels during both SEM and NEM at both spring and neap days.The lower level N. textilis population also rests significantly (P<o~ooi) higher than the high water levels around neap days during both GEM and NEM but were at a level non-significantly different from the high water during GEM around spring days. They rest significantly (P<0.001) lower than the tide level during NEM around spring days thus showing tendencies of the population to stay submerged around spring days during this season.