Q.Mention the distinguishing traits of class Hirudinea.

[!TLDR] Hirudinea (leeches) have anterior and posterior suckers, reduced/absent setae, fixed segment number, and a reduced coelom. …

[!ANSWER] Class Hirudinea (the leeches) shows a distinctive set of traits adapted to a parasitic or predatory habit.

Leeches possess anterior and posterior suckers, which they use both to attach firmly to a host or substrate and to move by a characteristic looping motion, alternately anchoring with each sucker. Unlike Polychaeta and Oligochaeta, Hirudinea largely or completely lack setae and lack parapodia altogether. The number of body segments in leeches is fixed and relatively small compared with the variable, often large segment counts of other annelids. Internally, the coelom of leeches is not a large, open, fluid-filled cavity as in Polychaeta and Oligochaeta; instead it is greatly reduced and filled with a spongy connective tissue (in places forming t …

• Assuming leeches have parapodia like polychaetes — they do not. …