Zoology 10th Edition by Stephen Miller,John Harley

تمرين 14

Members of the clade Clitellata include the earthworms, other oligochaetes, and leeches (clade Hirudinea). They lack parapodia, have few or no setae, and possess a clitellum. Oligochaetes use body-wall muscles in burrowing and crawling, feed as scavengers, have a closed circulatory system, have a ventral nervous system, and use metanephridia for excretion. Reproduction involves mutual sperm exchange by monoecious partners. Development is direct within cocoons. Leeches have a body wall with secondary divisions called annuli, complex musculature, and the coelom is not divided by septa. Leeches are predators whose internal functions are similar to those found in oligochaetes.
What is a parasite (see chapters 6 and 8)? Why is it more accurate to describe leeches as predators rather than parasites?