Population Dynamics of the Parasites in Fundulus zebrinus in the Platte River of Nebraska

Abstract

The population dynamics of 7 parasite species or ecotypes were studied in the plains killifish, Fundulus zebrinus, at a single collection site in the South Platte River of Nebraska, U.S.A., for 5 yr. Parasites were: Myxosoma funduli (gill), Trichodina sp. (gill), Gyrodactylus bulbacanthus (gill), Urocleidus fundulus (gill), Gyrodactylus stableri (body surface), and Neascus sp. (=Posthodiplostomum; eyes and body cavity). Parasite densities, prevalences, and variance/mean ratios are reported for 22 samples, totalling 447 fish, over the summer months. Positive correlations were obtained between density and both standardized prevalence and log-transformed variance. Urocleidus fundulus populations were relatively stable with low densities and low variance/ mean ratios. Most other species' populations exhibited disproportionate increases in aggregation with increases in density. The Neascus species showed long-term decreases in density and prevalence associated with increases in river flow rates. In the Platte River system of Nebraska, Fundulus zebrinus (=F. kansae Garman; see Poss and Miller, 1983) is host to a number ofparasite species (Knight et aI., 1980; Adams, 1985). Observations made from 1975 through 1981 suggested that these formed an assemblage whose members' population structures varied with collection date and site (Adams, 1985, and unpubl. data). The Platte system is a physical environment that is highly complex and variable, although both of these attributes are primarily functions ofstreamflow. The river thus provides an opportunity to investigate the dynamic behavior of several parasite species populations in a single host species, all in a fluctuating environment.