Abstract
This study examines the behaviour of Urocleidus adspectus on the gills of yellow perch (Perca flavescens). The adult worm is found firmly attached to the gills of the host with the haptor fitted snugly into an interlamellar space and with four large hamuli and 14 small marginal hooks impaled into the adjacent epithelium. The forebody of the worm is almost always directed downstream toward the tip of the primary lamella. The worm is a tissue feeder and the reach and flexibility of the forebody allow efficient grazing around any one site of attachment. Worms can graze farther by moving to a new site of attachment. This involves a leechlike movement in which the haptor and the head are alternately used as the organ of attachment. The movement is brief (3 s or less) and, most likely in response to the threat of dislodgment, only single relocations are made at any one time. The worm almost always comes to lie in the preferred adhesive attitude no matter what the direction of travel under natural conditions. However, under experimental conditions in which there was no water flow, the position was occasionally reversed.

This publication has 1 reference indexed in Scilit: