Dynamics of the Leptorhynchoides thecatus (Acanthocephala) Suprapopulation in a Great Plains Reservoir

Abstract

The suprapopulation of Leptorhynchoides thecatus occurred in 4 species of definitive hosts, Lepomis cyanellus, Lepomis gibbosus, Lepomis macrochirus, and Micropterus salmoides, and the intermediate host, Hyalella azteca, in Atkinson Reservoir, Nebraska. Prevalence was high (66%) in fishes and gravid females were present throughout the year. There were peaks in all measured population parameters during the spring (April- June) and autumn (September-November). Lepomis cyanellus appeared to be the principal definitive host for L. thecatus in Atkinson Reservoir. On the whole, more L. cyanellus were infected (89%), infections were relatively more dense (6.0), and the mean intensity (6.8) was higher than in the other species, and a larger percentage (42%) of the female worms was gravid. Relative output of L. thecatus eggs was greatest from L. cyanellus. Micropterus salmoides and L. gibbosus appeared to be most important during May and summer, respectively. Leptorhynchoides thecatus occurred in broodless H. azteca larger than 2.0 mm. In this portion of the amphipod population prevalence (0.7%), mean intensity (1.0), and relative density (0.01) were always low, but prevalence peaked in spring and autumn, corresponding with peaks in fishes. Visceral forms of L. thecatus occurred in all 4 centrarchid species but did not appear important to the dynamics of intestinal worms.