Pathology of five species of Gyrodactylus Nordmann, 1832 (Monogenea)

Abstract

Attachment-site pathology of the ectoparasites Gyrodactylus adspersi Cone and Wiles, 1983 on Tautogolabrus adspersus, Gyrodactylus avalonia Hanek and Threlfall, 1969 on Gasterosteus aculeatus, Gyrodactylus bullatarudis Turnbull, 1956 on Poecilia reticulata, Gyrodactylus sp. on Carassius auratus, and Gyrodactylus salmonis (Yin and Sproston, 1948) on Salmo gairdneri was examined using optical microscopy and scanning electron microscopy. In the first four species, the disc-shaped haptor attached itself to the host skin surface by means of blade tips of 16 peripherally located marginal hooks, with the two ventrally located hamulus blades compressing the underlying epithelium into a small depression. Tissue damage from attachment and feeding was minimal. However, G. salmonis lodged its marginal hook sickles deep into the host epidermis and appeared to cause extensive fin damage and skin discoloration. There was little evidence of bacterial involvement in the wounds, but bacterial microcolonies were observed on the body surface and haptor of G. salmonis. The latter results are discussed in relation to our understanding of gyrodactyliasis.