Feeding and digestive rhythms in intertidal bivalve molluscs, <i>Anadara rhombea</i> (Born) and <i>Crassostrea madrasensis</i> (Preston)

Abstract

Rhythmic changes in the morphology, length, protein content and dry weight of the crystalline style and histological changes undergone by the digestive tubules in <i>A. rhombea</i> and <i>C. madrasensis</i> are reported in relation to one complete tidal cycle. In both the species, crystalline style is completely lost during low tide and is reformed during high tide. At peak of the high tide, maximum values in length, protein content and dry weight occur in the style of both. <i>A. rhombea</i> and <i>C. madrasensis</i>. Digestive tubules in the two species show that intracellular digestion is also rhythmic and monophasic i.e. at a particular tidal phase almost all the tubules have a homogeneous structure. During high tide, the digestive tubules pass through digestive and absorptive phases while over the low tide regime the disintegrating and reformative phases are dominant indicating that these intertidal bivalves feed and digest rhythmically during high tides.