Patterns in helminth communities in freshwater fish in Great Britain: alternative strategies for colonization

Abstract

Examples of the apparently stochastic nature of freshwater fish helminth communities illustrating the erratic and unpredictable occurrence and distribution of many species are provided for six species of fish from several localities throughout Britain. By focussing on parasite colonization strategies two categories of helminths are recognized: autogenic species which mature in fish and allogenic species which mature in vertebrates other than fish and have a greater colonization potential and ability. Three groups of fish are distinguished: salmonids, in which helminth communities are generally dominated by autogenic species which are also responsible for most of the similarity within and between localities; cyprinids, in which they are dominated by allogenic species which are also responsible for most of the similarity within and between localities; and anguillids, whose helminth communities exhibit intermediate features with neither category consistently dominating nor providing a clear pattern of similarity. Recognition and appreciation of the different colonization strategies of autogenic and allogenic helminths in respect of host vagility and ability to cross land or sea barriers and break down habitat isolation, and their period of residence in a locality, whether transient or permanent, provides an understanding of, and explanation for, the observed patchy spatial distribution of many helminths. Comparison with other parts of the world indicates that colonization is a major determinant of helminth community structure.

Helminth community structure of the oven frog Leptodactylus latinasus (Anura, Leptodactylidae) from Corrientes, Argentina

“…L. latinasus, which can live temporarily in an aquatic habitat, and allogenetic species (e.g. larvae) with a definitive host including snakes, birds, and mammals, which can leave the immediate aquatic habitat (Esch et al 1988(Esch et al , 1997. Alternatively, G. repandum's high colonization is determined by adaptations of its complex life cycle to ensure transmission, without requiring an intermediate host.…”

The comparative ecology and biogeography of parasites

“…Parasites rely almost entirely on their hosts, in particular the definitive host in the case of helminths, for dispersal at both small to large spatial scales. Therefore, the vagility of the definitive host should be the main determinant of a parasite's dispersal potential [78]. For instance, all else being equal, when comparing helminth parasites that spend the first part of their life cycle in freshwater habitats, we would expect those using birds or mammals as definitive hosts to disperse more readily across the region than those using fish, as the latter remain more or less confined to a single water body.…”

Community ecology of the metazoan parasites of freshwater fishes of Kerala

“…It is to be noted in this context that the compound community of parasites (= local parasite fauna) is influenced by several factors and there could be even temporal differences in the nature of the compound communities (Holmes 1990). Further, there is evidence to show that the parasite communities of freshwater fishes are basically stochastic assemblages determined by events like chance introduction, colonization and extinction of parasites in a given region (Esch et al 1988;Hartvigsen and Kennedy 1993;Kennedy 1993). Carnivorous forms such as Channa spp., M. cupanus, Mystus spp.…”