Article
Article
Hirudinida
Article By:
Siddall, Mark E. Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, New York.
Last reviewed:January 2020
DOI:https://doi.org/10.1036/1097-8542.319100
The leeches, classified as a subclass of worms in the phylum Annelida (class Clitellata). Taxonomically, Hirudinida (also Hirudinea) is considered to be a subclass in the annelid class Clitellata (which also contains the subclass Oligochaeta and the order Branchiobdellida). There are two orders within Hirudinida—Arhynchobdellida (leeches that lack a protrusible proboscis) and Rhynchobdellida (leeches that possess a protrusible muscular proboscis). Anatomically, all leeches possess a clitellum employed in the secretion of their egg-case "cocoons," like the prominent "saddle" seen on earthworms, and DNA sequence data confirm that leeches are related closely to the lumbriculid oligochaetes. See also: Annelida; Arhynchobdellida; Branchiobdellida; Oligochaeta; Polychaeta; Rhynchobdellida
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