GENERAL HISTOLOGY

Detailed explanation-1: -All molluscs have a specialized foot used in digging, grasping, or creeping. The foot is a muscular organ modified into different forms in different molluscan classes (Fig. 3.53). Molluscs have a mantle or mass of soft flesh that covers the soft body and encloses the internal organs.

Detailed explanation-2: -A radula, a protrusible, rasp-like feeding organ present in most, but not all, species. In herbivorous mollusks (e.g., chitons and snails), the radula is used for scraping algae from rocks.

Detailed explanation-3: -Some species are parasitic. Shelled mollusks move around by means of a foot that they extend from the shell to contact the substrate, or the surface on which they live. The foot is a muscular extension of the ventral, or lower, side of the animal, and in many species it can be completely withdrawn into the shell.

Detailed explanation-4: -The broad, oval, flat foot is used for attaching to and creeping slowly over hard substrata. The mantle cavity is lateral and houses numerous gills. The head is small, lacking macroscopic sense organs and the nervous system consists of a circumgut ring and longitudinal cords, mostly without ganglia.