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Van Beneden, 1858

A very small worm of unique shape. A slender body of five unequal segments.
Prostomium is rounded and bears five appendages: three frontal oval antennae and two shorter ventral palps. Mouth between palps. Peristomium fused to prostomium, with a pair of ventrolateral cylindrical elongations, each terminating in a sucker. Three following segments apodous.
Segment 4 much longer than wide, contains the genital organs: in females an ovary, special glands, two oviducts and two genital pores ventrally; in males a pair of cylindrical modified parapodia (auxiliary copulatory organs), testes, two seminal vesicles, special glands, a pair of vase deferentia, and an unpaired muscular penis.
Segments 5 and 6 without parapodia, shorter. Last segment with a pair of large, cylindrical lateral parapodia, each with a small cirrus and a sucker.
Posterior end is broadly bifurcated, giving the worm the appearance of a pick-axe or anchor.
Mandibles with two long posterior rods, enlarged anteriorly with hooked lateral edges and finely toothed anterior margins. Maxillary carriers long, fused to each other. Basal maxillae hooked, each with three teeth. Three pairs of toothed plates.

Up to 1.5 mm for seven indistinct post-peristomial segments.


Parasitic in the gill chambers and among the eggs of lobsters.

English Channel (Roscoff) and south-western part of the North Sea.

Histriobdella homari