A predator's dilemma: prey choice and parasite susceptibility in three-spined sticklebacks.
The acanthocephalan parasite Pomphorhynchus laevis is transmitted by a suitable intermediate host such as the amphipod Gammarus pulex to its definitive fish host. Parasite-induced alterations in both appearance and behaviour concur to render infected gammarids more vulnerable to predation, thus promoting parasite transmission. Experimental infection of laboratory bred full- and half-sib groups of three-spined sticklebacks (Gasterosteus aculeatus) provided evidence that the parasite imposes a survival cost proportional to the severity of infection on its final host. Variation among sibships in the susceptibility to infection was consistent. When given a choice, fish consumed significantly more infected than uninfected prey. Overall, more resistant fish did not prey upon infected gammarids more often than did relatively susceptible fish. Only fish with a relatively high physical condition properly adjusted prey selection to the extent of their parasite susceptibility, thus exploiting the enhanced profitability of infected prey.
Division of Behavioural Ecology, Institute of Zoology, University of Bern, Wohlenstrasse 50a, CH-3032 Hinterkappelen, Switzerland. Dominique.Mazzi@ebc.uu.se
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D000049:Acanthocephala / Q000502:physiology; D000818:Animals; D002755:Choice Behavior; D004198:Disease Susceptibility; D004199:Disease Vectors; D005260:Female; D005393:Fish Diseases / Q000401:mortality / Q000469:parasitology* / Q000635:transmission; D005399:Fishes / Q000469:parasitology* / Q000502:physiology*; D006790:Host-Parasite Interactions; D008297:Male; D011235:Predatory Behavior