Relationship Between Habitat Structure and the Distribution and Abundance ofPaulisentis missouriensis(Acanthocephala) in Creek ChubSemotilus atromaculatus

Abstract

Paulisentis missouriensis (Acanthocephala) occurs in creek chub Semotilus atromaculatus in 2 drainages, South Fork and Turkey Creek, of the Big Nemaha River system in southeastern Nebraska, U.S.A., but not in 2 other drainages, Muddy Creek and North Fork. The present investigation tested the hypothesis that stream habitat characteristics limit P. missouriensis to the South Fork and Turkey Creek drainages. Habitat characteristics were compared between sites in drainages where the worm occurs and where it is absent, with pools being significantly larger and more closely spaced in drainages with the worm. Within Turkey Creek, where the worm is modestly abundant, metrics describing pool size were significantly correlated with abundance of P. missouriensis. However, this effect was primarily due to the influence of 1 site, and the relationship was not evident when the drainage where the worm is abundant (South Fork) was included; in these analyses, variables describing water chemistry (oxygen concentration and total water hardness) were significantly associated with abundance of P. missouriensis. Characteristics of pool habitats appear to be able to explain the absence of P. missouriensis in the Muddy Creek and North Fork drainages, but these same characteristics are not as closely associated with variation in the abundance of P. missouriensis in the South Fork and Turkey Creek drainages where the worm is found.