The functional morphology of the copulatory apparatus of Ergenstrema labrosi and Ligophorus angustus, monogenean gill parasites of Chelon Labrosus

SUMMARYThe male intromittent apparatus of Ergenstrema labrosi and Ligophorus angustus, monogenean parasites of the thick-lipped grey mullet Chelon labrosus, consists of a slender flexible penis tube with an expanded proximal region and whose distal end passes freely through a canal in an accessory sclerite; the tube is surrounded by a sleeve of longitudinal muscle and the apparatus works in a manner generally similar to an engineer's Bowden cable. There is a substantial difference in the form of the accessory sclerite in the two species. In both parasites there is a slender sclerotized vagina which, in L. angustus, is short and straight or curved but in E. labrosi is about 7 times longer and forms a spiral. The special role of the sclerotization of the distal part of the vagina may be to resist perforation of the wall by the exceedingly fine penis tube and the consequent discharge of sperms into the parenchyma.

The attachment of the monogenean Entobdella soleae to the skin of the common sole

The muscular saucer-shaped haptor of the monogenean parasite Entobdella soleae is attached to the skin of its host Solea solea by means of a suction pressure generated within the sea-water-filled cavity enclosed between the cup-shaped haptor and the skin of the fish. The suction pressure is produced by the action of a pair of extrinsic muscles which are situated in the body of the parasite. Each extrinsic muscle communicates with the haptor by means of a long tendon which passes through a fair-lead in a prop-like accessory sclerite and is inserted on the end of a girder-like anterior hamulus embedded in the roof of the concavity of the haptor. The pull exerted by the muscles lifts the girders and the roof of the suction cup in which they are embedded relative to the props, thereby producing a suction pressure.An electron microscope was used to investigate the ultrastructure of the tendon, which was found to consist largely of unbranched banded fibrils which differed from the collagen fibrils of vertebrate tendon in their diameter and periodicity.I would like to express my thanks to Dr J. Llewellyn for suggesting the problem and for much helpful discussion. I am also grateful to Dr M. P. Osborne for tuition on the cutting of sections for electron microscopy. The work was conducted during the tenure of a Fishery Research Training Grant from the Development Commission.