University of Khartoum

Morphology and Epidemiology of Some Parasitic Cope Pods (Poecilostomatoida: Ergasilidae) From British Freshwater Fish

Morphology and Epidemiology of Some Parasitic Cope Pods (Poecilostomatoida: Ergasilidae) From British Freshwater Fish

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Title: Morphology and Epidemiology of Some Parasitic Cope Pods (Poecilostomatoida: Ergasilidae) From British Freshwater Fish
Author: Abd Elhalim, A. I.
Abstract: The morphology of the parasitic female Ergasilus sieboldi Nordmann 1832 and Neoergasilus japonicus Harada 1930 together with the free-living stages of E. sieboldi are described using scanning electron microscopy. In both species cuticular outgrowths such as setae, setules, spines, spinules and sensillae as well as the integumental pores and openings were clearly identified. Studies on E. sieboldi indicated that the first leg-bearing somite is totally separated from the cephalosome. six morphologically different nauplii of E. sieboldi were identified, in addition to five copepodidand a cyclopoid stage. Sex differentiation occurs in the fourth copepodid stage and mating of adult cyclopoid male and female occurs in water. Females with attached spermatophores enter parasitic life by finding hosts and males die. The extent of tissue damage caused by the feeding activities of E. sieboldi and N. japonicus on the gills and fins of fish, respectively, is described using light and scanning electron microscopy. Such pathology, of E. sieboldi, include epithelial cell proliferation and hyperplasia which lead to fusion of gill secondary lamellae and eventually the fusion of the neighbouring gill filaments, metaplasia and necrosis. The attachment strategy of E. sieboldi results in blockage and destruction of blood vessels and opens wounds which might facilitate invasion of pathogenic microorganisms. N. japonicus destroys the covering mucus layer and erodes the epidermis of the skin by feeding and also paves way for pathogenic bacteria and fungi, by the action of second antennae. 15 The intensity and distribution of E. sieboldi on the gills is described from four species of freshwater fish, namely Tinca tinca, Abramis brama, Cyprinus carpio and Esox luciuSi from the Middle Thames Valley in Southern England. A similar ecological study was also undertaken on N. japonicus from the fins and gills of five species of freshwater fish, namely A. brama, T. tinea, E. lucius, Rutilus and Scardinius erythrophthalmus; from the same region. • An experimental study on development and establishment of E. sieboldi on rainbow trout, maintained in an open cage uni t under field conditions, is described. In addition seasonal occurrence of the different free-living stages is studied from laboratory experiment. Results from both field and laboratory experiments indicate that E. sieboldi is reproductively active from March to October during which period fish are continually infected.
URI: http://hdl.handle.net/123456789/595
Date: 1990


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