Amphibdellid (monogenean) parasites of electric rays (Torpedinidae)

Abstract

Electric rays (Torpedinidae) are known to harbour on their gills certain monogenean parasites (Amphibdella spp. and Amphibdelloides spp.) whose taxonomy is in a very confused state. Muchof this confusion has centred around a single morphological feature: a ‘transverse bar’ has been variously held to be present or absent from the adhesive apparatus, or sometimes two such bars have been stated to be present. Among those who have regarded the trans-verse bar as having taxonomic importance, Price (1937) recognized two genera of amphibdellids distinguishable by the presence or absence of the bar, but Palombi (1949) and Bychowsky (1957) believe that the bar may be present in young specimens but absent or inconspicuous in older specimens. No-one has investigated the function of thistransverse bar, or, indeed, any functional aspect of the adhesive apparatus. Again little attention has been paid in taxonomy to the genitalia or host specificity, or, in spite of a record of an amphibdellid from the heart of its host, to micro-habitat.

Attachment ability of a clamp-bearing fish parasite, Diplozoon paradoxum (Monogenea) on gills of the common bream Abramis brama

“…Although some muscles present in the monogeneans are presumed to be able to perform continuous contraction (Halton et al, 1998;Kearn, 1966), this would hinder or stop the probing or searching movement of the monogeneans. Similar problems of such continuous contraction of extrinsic muscles, associated with the haptoral attachment apparatus in monogeneans, have also been noted in other studies (Llewellyn, 1960;Kearn, 1966;Halton et al, 1998). In addition, if one end of the extrinsic muscles were not 'fixed' or attached to a stiff support, the contraction of the extrinsic muscles, associated with the clamps, would only cause the retraction of the monogenean body instead of closing its clamps.…”

“…These unique haptoral attachment apparatus have encouraged many scientists to investigate how they operate efficiently. Several studies have been undertaken to elucidate the attachment mechanism of the anchors (Llewellyn, 1960;Kearn, 1971), marginal hooks (Shinn et al, 2003;Arafa, 2011), clamps (Cerfontaine, 1896;Llewellyn, 1956;Llewellyn, 1957;Llewellyn, 1958;Llewellyn and Owen, 1960;Owen, 1963a;Bovet, 1967), squamoid discs (Paling, 1966;Sánchez-García et al, 2011) and haptoral secretions (Rand et al, 1986;Wong et al, 2008). However, conclusions about the functional principles of the attachment apparatus are mainly based on morphological investigations of the attachment apparatus and associated muscular systems.…”

Surface Topography of the Anterior Adhesive Apparatus of the Gill Monogenean Parasite Diplectanum sp. diesing, 1858, with some Surface Criteria

“…In the monocotylid monogeneans Empruthotrema raiae and E. torpedinis, which inhabit the nasal fossae of their elasmobranch hosts, the gland ducts open into three eversible adhesive sacs on each side of the head region [10]. The adhesive sacs may indirectly assist feeding by firmly attaching the head region to the host and by holding the mouth in the feeding position, a function for the anterior adhesive apparatus which has been suggested by [11,12]. However, [13] noted that the anterior adhesive areas of Entobdella soleae appear not to be attached to the host while feeding is taking place.…”

Benedenia rohdei n. sp. (Monogenea: Capsalidae) from the gills of Lutjanus carponotatus (Perciformes: Lutjanidae) from the Great Barrier Reef, Queensland, Australia, with a description of the oncomiracidium

“…Sclerotised structures associated with the male copulatory organs of monogeneans may serve one or more of the following functions: a tubular sclerotised ejaculatory duct or an accessory rod-shaped sclerite may provide rigidity during intromission; sclerites may provide a firm basis for muscle insertion; hooks or opposable jaws may serve to hold parasites together during copulation (Llewellyn, 1960); and hooks or tubular sclerites may be involved in hypodermic impregnation (Macdonald & Caley, 1975;Llewellyn, 1983). The penis sclerite of B. rohdei bears little resemblance to any of the structures considered above and, consequently, it is difficult to ascribe a function.…”