|SREL Reprint #0490|
Relationship Between Thermal Loading and Parasitism in the Mosquitofish
M. Aho, J. Whitfield Gibbons, and Gerald W. Esch
The relationship between thermal loading and
parasitism was examined in 980 mosquitofish, Gambusia affinis,
taken from areas of varying thermal conditions at the Savannah River Plant (SRP)
near Aiken, S.C. Collections were
made at 2-week intervals from May to August 1974 and again from January to
February 1975. The metacercaria of
two Strigeid trematodes, Ornithodiplostomum ptychocheilus
and Diplostomum scheuringi were the only species of parasites
ptychocheilus was always found encysted in the brain and eyes, whereas D.
scheuringi was restricted exclusively to the body cavity.
The density of the body-cavity parasite was highest in fish from areas of
ambient temperatures and declined in fish from areas with higher water
temperatures. The density of the
brain parasite, on the other hand, was higher in fish from areas directly
receiving thermal effluent than in fish from ambient-temperature areas.
The body-cavity parasite was absent from mosquitofish from Pond C, but
the infection percentages were relatively consistent in fish from other areas in
the Par Pond system regardless of water temperature.
The brain metacercaria were recovered from 95% of fish from Pond C.
There were higher infection percentages of brain parasites in fish from
thermally altered areas of Par Pond than in those from other parts of the Par
Pond system. Three different
hypotheses can be formulated to account for the relationship between thermal
loading and the observed abundance and distribution patterns for these two
species of parasites: (1) a direct
differential influence of temperature on the physiological tolerance of the
various life-cycle stages of the parasite; (2) a direct differential impact of
temperature on the distribution of the molluscs that serve as the first
intermediate hosts; and (3) an effect of temperature on the abundance and
distribution of the potential definitive hosts within the study area.
Keywords: Par Pond Reservoir System
SREL Reprint #0490
Aho, J.M., J.W. Gibbons, and G.W. Esch. 1976. Relationship between thermal loading and parasitism in the
mosquitofish. p. 213-218. In Thermal Ecology II, edited by G.W. Esch and R.W.
McFarlane. CONF 750425. ERDA