Occurrence of the metacercariae of Cotylurus erraticus (Rudolphi, 1809) Szidat, 1928 (Digenea: Strigeidae) in brown trout Salmo trutta L., and rainbow trout S. gairdneri Richardson, 1836, from Hanningfield Reservoir, Essex

A report on various digenetic metacercariae from the freshwater fishes of River Godavari, Rajahmundry

Fishes serve as intermediate hosts to a number of avian digenetic trematodes. A survey on 10 different species of freshwater fishes belonging to 8 families from River Godavari from August 2005 to September 2007 revealed a total of 10 metacercariae of digenetic trematodes from five families i.e., Clinostomidae Lühe, 1901; Diplostomidae Poirier, 1886; Isoparorchiidae (Travassos, 1922); Strigeidae Railliet, 1919 and Heterophyidae (Leiper, 1909) Odhner, 1914. The metacercarial fauna dominated the adult parasitic fauna of the freshwater fishes.

Ichthyocotylurus erraticus (Digenea: Strigeidae): factors affecting infection intensity and the effects of infection on pollan ( Coregonus autumnalis ), a glacial relict fish

Lough Neagh pollan are heavily infected with the strigeid Ichthyocotylurus erraticus , with 100% prevalence and median infection intensities of 600+ metacercariae in the pericardial cavity of mature fish. Female fish were more heavily infected than males. Infection intensity, which rose in summer, varied with pollan size, year, sampling bay within the lough and water depth within bays. Heavily infected pollan were caught further offshore than lightly infected fish. Spatial variation in pollan infection intensity corresponded to variation in the abundance of the first intermediate host, Valvata snails. The data suggest that heavily infected fish had lower food intakes. Parasitism reduced condition and liver size in male fish but condition in heavily parasitized females increased. Infection intensity was greater in larger fish of a given age. These patterns are discussed in the context of risks and rewards. The data suggest that inshore waters in summer are the preferred habitat of pollan and that the greater infection intensity of offshore fish results from their reduced competitive ability as a consequence of parasitism and the increased risk of infection there.

Patterns of macroparasite abundance and aggregation in wildlife populations: a quantitative review

In this paper we review the published literature on patterns of abundance and aggregation of macroparasites in wildlife host populations. We base this survey on quantitative analyses of mean burden and a number of measures of the degree of aggregation of parasite burdens between hosts. All major parasite and vertebrate host taxa were represented in the database. Mean parasite burden was found to be log-normally distributed, indicating that all parasite burdens are regulated to some degree. In addition, all but one of the parasitic infections were aggregated with respect to their hosts, and the relationship between log mean parasite burden and log variance was found to be very strong (R2= 0·87). That is, for a given mean parasite burden there are constraints on the degree of variation in individual host burdens. The aggregated nature of the parasitic infections is also apparent from other measures of the degree of aggregation: prevalence – mean relationships, and the negative binomial parameter,k. Using a relatively new technique for parasitological infection data – tree-based models, as well as traditional linear models – a number of the parasitic infections was found to be associated with systematically lower or higher parasite burdens. Possible biological explanations for these and other patterns are proposed.

A checklist of metazoan parasites from rainbow trout (Oncorhynchus mykiss)

An extensive literature survey on metazoan parasites from rainbow trout Oncorhynchus mykiss has been conducted. The taxa Monogenea, Cestoda, Digenea, Nematoda, Acanthocephala, Crustacea and Hirudinea are covered. A total of 169 taxonomic entities are recorded in rainbow trout worldwide although few of these may prove synonyms in future analyses of the parasite specimens. These records include Monogenea (15), Cestoda (27), Digenea (37), Nematoda (39), Acanthocephala (23), Crustacea (17), Mollusca (6) and Hirudinea (5). The large number of parasites in this salmonid reflects its cosmopolitan distribution.