Seasonal population dynamics of five species of intestinal helminths of the brook stickleback, Culaea inconstans

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Abstract
Seasonal changes in populations of five species of enteric helminths that parasitize the brook stickleback (Culaea inconstans) were studied during a 14-month period in Wisconsin. The trematodes Bunodera eucaliae, B. luciopercae, and immature Halipegus sp., the acanthocephalan Neoechinorhynchus pungitius, and the larval cestode Proteocephalus sp. each displayed pronounced seasonal patterns of prevalence in Sioux Creek sticklebacks. Bunodera eucaliae, the most abundant species, infected sticklebacks in early summer. By late summer, most B. eucaliae had completed egg production and were expelled from their hosts. Some B. eucaliae overwintered in sticklebacks and completed development in late spring. In contrast, B. luciopercae displayed low prevalence in sticklebacks and produced eggs at the coldest period of the year. The relative density of N. pungitius increased throughout fall and winter. These acanthocephalans were most numerous and attained maximum development in late spring. Unencysted metacercariae of Halipegus sp. parasitized sticklebacks in midsummer but thereafter declined in relative density. Sticklebacks possibly acted as paratenic hosts for H. eccentricus which occur commonly in Rana pipiens and R. clamitans in Sioux Creek. A few sticklebacks harbored Proteocephalus sp. plerocercoids in midsummer but this parasite was virtually absent throughout the remainder of the year.