EGG LAYING BEHAVIOUR OF BULINUS OCTOPLOIDUS BURCH (BASOMMATOPHORA: PLANORBIDAE)

Egg laying behaviour of Bulinus octoploidus in the laboratory comprises three phases: (1) grazing, (2) deposition and (3) sweeping. The grazing phase lasts about 60–90 min and can be recognized by the slowness of forward movement, movement in a restricted area, extended pseudobranch, and regular radular movements against the substratum. Radular movements stop only during turns and have a maximum frequency of about 45 min−1. Egg mass deposition occurs at the end of the grazing phase and is accomplished in 1 min or less. Egg mass sweeping is a post-deposition phase lasting 8—12 min, during which the snail “sweeps” back and forth across the egg mass, apparently to anchor and flatten it.