Intrinsic Host Factors and the Distributional Limit ofPaulisentis missouriensis(Acanthocephala) in Southeastern Nebraska, U.S.A

Abstract

Paulisentis missouriensis is a common acanthocephalan parasite of creek chub (Semotilus atromaculatus) in the streams of 2 drainages (South Fork and Turkey Creek) in the Big Nemaha River system in southeastern Nebraska, U.S.A., but is absent from streams in the remaining 2 drainages (Muddy Creek and North Fork). The present investigation tested whether intrinsic host-related factors are responsible for the distributional limit of P. missouriensis in this system. Copepods and creek chub were collected from streams where the worm is absent and exposed to infective stages of P. missouriensis under laboratory conditions. In addition, creek chub from areas lacking the worm were maintained in cages in a stream where the worm is abundant. Both creek chub and copepods from streams lacking the worm became infected under laboratory and field conditions. These results reject the possibility that the cause of the abrupt distributional limit of P. missouriensis in the Big Nemaha River system is due to intrinsic host-related phenomena. Other hypotheses that could account for the distributional limit include differing transmission conditions among drainages, environmental limits on completing development, and long-term spatiotemporal factors.