How do aquatic annelids remove nitrogen wastes?

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annelid *The structure of polychaetes.* (Left) Free-moving polychaetes. (A) *Neanthes,* (B) *Nereis.* (Right) Tube-dwelling (sedentary) polychaetes. (C) *Amphitrite,* (D) *Sabella.*

Aquatic annelids primarily remove nitrogenous waste in the form of ammonia, which is the main end product of their protein metabolism.1

This excretion is managed by their excretory system, which consists of either protonephridia or metanephridia. These structures function similarly to the vertebrate kidney through processes of filtration, resorption, and secretion. For example, in the sea mouse, approximately 80 percent of nitrogen is excreted as ammonia. Similarly, leeches primarily excrete ammonia, some of which may be produced by bacteria residing within their nephridial capsules.1