Clitellum

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The clitellum is a thickened glandular and non-segmented section of the body wall near the head in earthworms and leeches that secretes a viscid sac in which eggs are stored. It is located near the anterior end of the body, between the fourteenth and seventeenth segments. The number of the segments to where the clitellum begins and the number of segments that make up the clitellum are important for identifying earthworms. In microdrile earthworms, the clitellum has only one layer, resulting in a smaller quantity of eggs than that of the megadrile earthworms, which have larger multi-layered clitellum that have special cells that secrete albumin into the worm's egg sac. The clitellum is part of the reproductive system of clitellates, a subgroup of annelids which contains oligochaetes (earthworms) and hirudineans (leeches). The clitellum is a thick, saddle-like ring found in the epidermis (skin) of the worm, usually with a light-colored pigment. To form a cocoon for its eggs, the clitellum...

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