Branchiobdellida

Article By:

Gelder, Stuart R. Department of Biology and Zoology, University of Maine, Presque Isle, Maine.

Last reviewed:October 2019

DOI:https://doi.org/10.1036/1097-8542.900175

An order of freshwater, obligate, ectosymbiotic clitellate annelids known as the crayfish worms. Branchiobdellidans form a monophyletic group within a larger clade including the Acanthobdellida and Hirudinida; the Lumbriculida constitute their sister group. Branchiobdellidans lack chaetae and a prostomium (the portion of the head anterior to the mouth or peristomium). They have 15 segments and a pair of dorsoventral jaws. Although they move leechlike, the anterior attachment site is the ventral surface of the ventral peristomial lip and not the oral region as in leeches. The male and female reproductive systems are found in body segments 5--7, with the male accessory organs and female spermatheca (sperm receptacle) both being unpaired. The taxonomic position of the Branchiobdellida in the Clitellata is an order located between the Lumbriculida and the Hirudinea. The order contains one family, Branchiobdellidae, with 4 subfamilies, 21 genera, and about 140 species. Zoogeographically, 15 genera have been recorded in the Nearctic and 6 in the Palearctic regions, with with no endemic genera being common to both regions. See also: Annelida; Hirudinida

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