Sexual segregation of Echinorhynchus borealis von Linstow, 1901 (Acanthocephala) in the gut of burbot (Lota lota Linnaeus)

Abstract

Abstract:Helminths often occupy defined niches in the gut of their definitive hosts. In the dioecious acanthocephalans, adult males and females usually have similar gut distributions, but sexual site segregation has been reported in at least some species. We studied the intestinal distribution of the acanthocephalan Echinorhynchus borealis von Linstow, 1901 (syn. of E. cinctulus Porta, 1905 in its definitive host, burbot (Lota lota Linnaeus). Over 80% of female worms were found in the pyloric caeca, whereas the majority of males were in the anterior two-thirds of the intestine. This difference was relatively consistent between individual fish hosts. Worms from different parts of the gut did not differ in length, so site segregation was not obviously related to worm growth or age. We found proportionally more males in the caeca when a larger fraction of the females were found there, suggesting mating opportunities influence gut distribution. However, this result relied on a single parasite infrapopulation and is thus tentative. We discuss how mating strategies and/or sexual differences in life history might explain why males and females occupy different parts of the burbot gut.

Differences in parasite community composition support ecological differentiation in a freshwater gadoid fish

“…The parasite communities of both littoral and profundal fish were dominated by nematodes and the acanthocephalan E . borealis , the latter being transmitted to burbot via the benthic crustacean Pallasea quadrispinosa found in deep lake basins (Tuomainen et al, 2015). Thus, the spatial overlap of adult burbot and the parasite's intermediate host is the likely reason for the observed similar patterns of infections in littoral and profundal fish.…”