Helobdella robusta. Helobdella robusta

Helobdella robusta, like all leeches, is distinguished from other annelids by anterior and posterior suckers used for locomotion and feeding on blood or soft body parts of other animals. It is an experimentally tractable and well-studied model organism representative of the spirally cleaving taxa (chiefly annelids, molluscs, and non-acoel flatworms), is small (1-3 cm in length), and breeds year round in laboratory culture, feeding on small freshwater snails. Comparisons of Helobdella and regenerating oligochaetes such as Tubifex provide an excellent case study for studying the changes associated with the loss of regenerative capabilities, similar to that seen in the evolution of mammals from their vertebrate ancestors.