The structure and mode of action of the posterior adhesive organ of Pseudobenedenia nototheniae Johnston, 1931 (Monogenea: Capsaloidea)

• Published in: Parasitology
• Main Authors: Williams, I. C., Ellis, C., Spaull, V. W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1973
• Subjects: Infectious Diseases; Animal Science and Zoology; Parasitology; Anchorage; South Orkney Islands
• Online Access: http://dx.doi.org/10.1017/s0031182000046035; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0031182000046035

An account is given of the structure and mode of action of the opisthaptor of the monogenean Pseudobenedenia nototheniae Johnston, 1931, from the skin of the fish Notothenia neglecta , caught in December 1969 at a depth of 40 m offSigny Island (60° 43′ S., 45° 36′ W.), South Orkney Islands. The opisthaptor has a roughly hexagonal central loculus surrounded by a septum which is continuous with six radiating septa. It is armed with 14 marginal hooklets and three pairs of sclerites which function as anchors. The opisthaptor obtains adhesion through gripping the host's skin with the muscular rim, and through close contact by the marginal membrane. These form a water-tight seal, the surface area of which is about one-quarter of that of the ventral surface of the opisthaptor. The seal enables the opisthaptor to function as an underwater sucker. Contraction of muscles associated with the opisthaptor, in particular the extrinsic muscles, can generate a pressure difference across the wall of the opisthaptor some 50 times greater than that required to support the weight of the parasite, thus suggesting that reserves are available to resist dislodging forces such as increased water flow. The instability and tendency to slide of the sucker is counteracted by anchorage from the hooklets and sclerites. The structure and mode of action of the opisthaptor of P. nototheniae are discussed in relation to studies made by other authors on similar adhesive organs.