metanephridium tubule
Quick Summary
A metanephridium tubule is a component of the excretory system found in more complex, segmented invertebrates like earthworms. Unlike simpler protonephridia, metanephridia lack a flame cell and open directly into the body cavity.1
Cilia lining the metanephridium tubule draw fluids from the body cavity and transport them to the exterior. During this process, the tubule cells actively reabsorb useful nutrients. In annelids, these tubules function similarly to vertebrate kidneys, involving filtration, reabsorption, and secretion. The primary nitrogenous waste product excreted by aquatic annelids is ammonia, while earthworms, adapted to soil, excrete more urea.12
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