Spatio-temporal dynamics of the parasitic nematode Anguillicola crassus in Flanders, Belgium

[摘要] ABSTRACT: Despite Egusa¹s earlier warning of the damage that the parasitic nematode Anguillicola crassus could inflict on the European eel Anguilla anguilla, its introduction in Europe was a fact in the early 1980s. Based on an elaboratedataset on Anguillicola crassus infection of 11 river catchments, this paper presents the results of a detailed study on the dispersal of the parasite in Flanders, Belgium, and the host-parasite relationship. In addition, data from 1986 and 1997are used for comparative purposes, providing a perspective on the temporal infection pattern over 15 yr. The presence of A. crassus in Flanders was first discovered in 1985; 2 yr later a survey revealed a prevalence of 34.1% and a mean infectionintensity of 5.5, based on adult nematodes only, and 10 yr later the parasite was present at all 11 sites sampled. Prevalence had increased to 62.5% but the mean infection intensityhad decreased to 3.9 adults per infected eel. Finally, in the year 2000,a third study revealed that A. crassus was present in 139 of 140 investigated sites; a further increase in prevalence to 68.7% and a decrease in mean infection intensity to 3.4 adults per infected eel was observed. When all larval stages weretaken into account, mean prevalence amounted to 88.1% and mean intensity to 5.5 adults. The high infection level in Flanders is thought to be the result of restocking with glass eel and yellow eel, both of which are susceptible to A. crassus. Thegeneral infection parameters were similar in all 11 river catchments. It is possible that in Flanders both prevalence and mean infection intensity are stabilizing due to density-dependent regulation of the parasite infrapopulation. Fibrotic swimbladderwalls were observed, mainly in large eels, and 20% of the total number of nematodes consisted of encapsulated larvae in the surveys of 1997 and 2000; 8 cases of swimbladder regeneration were observed.

[学科分类] 生物科学（综合）

[关键词] European eel;Exotic species;Host-parasite evolution;Mean intensity;Parasite;Prevalence