Population Composition and Dispersal Pattern of Pomphorhynchus bulbocolli in Hypentelium nigricans from the West Fork of Drake's Creek, Kentucky

Abstract

The seasonal prevalence and intensity of infection, infrapopulation composition and dispersal pattern of Pomphorhynchus bulbocolli were studied in Hypentelium nigricans from the West Fork of Drake's Creek, Kentucky. From February 1977 through November 1981, 165 H. nigricans were collected and examined. The prevalence of P. bulbocolli was 81.2%o and the mean intensity was 30.68 i 3.43. No significant differences were observed in the prevalence or intensity of infections in male and female H. nigricans. There were significant differences in the seasonal prevalence and mean intensity of infection; both were low in winter and high in summer. The sex ratio was relatively constant in all seasons with infrapopulations composed of slightly more females than males. Gravid females were recovered during all seasons. The smallest mean body lengths of both sexes occurred in the summer. This, with the highest seasonal mean intensity of infection, indicated that summer was the season of maximum recruitment. There was a positive correlation between total length of H. nigricans and the number of P. bulbocolli but not between the coefficient of condition of the fish and the number of parasites. Pomphorhyncus bulbocolli were clumped (overdispersed) in the H. nigricans population. INTRODUCTION The acanthocephalan, Pomphorhynchus bulbocolli Linkins, is a common endohelminth of fishes in the eastern United States; it has been reported from 81 host species (Samuel et al., 1976). The ecology of P. bulbocolli has been described in white suckers Catostomus commersoni Lacepede, from both lentic (Lawrence, 1970) and lotic environments (Muzzall, 1980). The present report is directed at the seasonal prevalence and intensity of infection, infrapopulation composition and dispersal pattern of P. bulbocolli in the northern hogsucker Hypentelium nigricans (Lesueur) from a small lotic environment in S-central Kentucky. MATERIALS AND METHODS From February 1977 to November 1981, northern hogsuckers were collected from the West Fork of Drake's Creek, 12 km N of Franklin, Simpson Co., Kentucky. The collection station consisted of a stretch of four riffles and three pools, approximately 150 m long, bisected by a low-water bridge. At the station, Drake's Creek is an Order IV stream, with a substrate of gravel and bedrock. It is a part of the Barren River drainage. The amphipod intermediate host, Gammarus pseudolimnaeus Bousfield, occurs in large numbers in the riffle areas. Fish were collected by electrofishing and seining. After return to the laboratory, fish were killed and the weight, total length and sex were determined. The intestinal tract was removed intact and divided into the regions A, B, Cl, C2, C3 and C4, as described by Amin (1975). The tract was opened and the number and location of Pomphorhyncus bulbocolli determined. The parasites were placed in distilled water at 7 C for 48-96 hr and then fixed in A.F.A. Whole mounts of worms with intact trunks were made using standard techniques. The trunk length, sex and state of maturity of each specimen were determined. Females were classified as being immature (ovary intact), mature (ovarian balls present) or gravid (shelled acanthors present). Males with sperm in the seminal vesicle were classified as mature and those without sperm as immature.