Description
The etymology behind the word “gastropoda” comes from the Greek word gaster, meaning stomach and podos, meaning foot. This is in relation to the position of gastropods’ foot. Gastropods are one of the most diverse groups in the animal kingdom and the largest group of molluscs. There are over 62,000 living species, making up about 80% of the living mollusc population. The diagnostic characteristic of gastropods is its “stomach foot” in which its body and internal organs are twisted back so that the stomach lies above their muscular foot.
Physical Features
Gastropods are usually sluggish, sedentary animals because most of them have heavy shells and slow locomotion. They may be protected by shells, by distasteful or toxic secretions, and/or by secretive habits. All gastropods have a well-developed head with eyes and 1-2 pairs of tentacles. They are soft-bodied animals, without body segmentation, and most have a single external shell made of calcareous material. Their torsion leads to a condition of bilateral asymmetry in adult gastropods. Most gastropods are herbivorous, by which they get their food rasping particles of algae from hard surfaces, using their radula.