Family HISTRIOBDELLIDAE

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Family HISTRIOBDELLIDAE

Compiler and date details

Jan 2011 - P. Hutchings & M. Yerman, Australian Museum, Sydney, New South Wales, Australia

23 July 2003

Introduction

Histriobdellids are a small group of polychaetes that live commensally on marine and freshwater crustaceans. They are found among the branchial filaments, pleopods or egg masses of their hosts, their precise location depending on the species. Their name can be loosely translated as "clown animals" which refers to the way in which these animals crawl. They are small (0.5–1.5 mm long), transparent, lacking chaetae, but distinguished by dark chitinous jaws.

Figures of 1 genus and 2 species were given by Beesley et al. (2000: App. 1) for representation of the family in Australian waters, and 3 genera and 11 species worldwide. Two species are described from Australian waters, but given their small size and their specialised commensal habitat they may be more common than their current distribution records suggest.

See Paxton (2000) for detailed treatment of the family.

Database Notes

proof read against Day & Hutchings 1979 by RW
checked against DELTA CD 2003 by RTJ

Diagnosis

General features. Body shape vermiform; segments few (typically 7 to 14); regionation absent. Pygidium deeply cleft forming two large feet.
Head & head structures. Head discrete and compact, dorsal to mouth. Prostomium rounded to oval (anteriorly truncate). Eyes absent. Prostomial antennae present; three arising posteriorly; smooth. Palps paired; unarticulated; dorsolateral. Nuchal organs absent, or present; indistinct paired dorsolateral patches. Peristomial ring single; cirri present, 1 pair (laterally positioned adhesive organs).
Pharynx & pharyngeal apparatus. Foregut a ventral pharyngeal organ; with multiple jaw elements of different shapes and sizes; comprising ventral mandibles and dorsal maxillae; maxillae 4–5 pairs of toothed plates in parallel rows (plates very small and not always toothed); maxillae symmetrical; maxillary carriers similar in length to combined length of maxillae; dorsolateral ciliated folds present.
Body segments & parapodia. First segment a smooth ring. Parapodia absent. Dorsal cirri more-or-less cirriform (assumed to be cirri). Ventral cirri present, cirriform or tapering (assumed to be cirri). Branchiae absent.
Chaetae. External chaetae absent. Aciculae absent.

The above description was generated from: 'C.J. Glasby & K. Fauchald (2002 onwards). POLiKEY. An information system for polychaete families and higher taxa: Version 1: September 2002.'
(See ABRS website: Online Resources: Polikey, for Version 2, released June 2003)