Effects of two parasites, Schistocephalus solidus (Cestoda) and Bunodera spp. (Trematoda), on the escape fast-start performance of three-spined sticklebacks
The fast-start performance of three-spined sticklebacks Gasterosteus aculeatus infected with Schistocephalus solidus and Bunodera spp. was determined and two distinct fast-start responses (A and B) were observed. ‘A’ starts were of higher flexibility than B and three-way ANOVA showed significant effects of A and B starts (P < 0·05), time (P < 0·05) and per cent standard body length, LS (P < 0·05) on the orientation angle (angle of an individual segment of the fish with respect to the direction of travel). Schistocephalus solidus infection reduced maximum velocity (P < 0·05) and maximum acceleration (P < 0·05) of infected fish. Uninfected fish and fish infected with S. solidus up to a parasite index (parasite mass divided by the sum of fish and parasite mass) of 0·1 executed both types. Infected fish exclusively executed B starts for parasite index between 0·1 and 0·2. This was not due to a reduction in body flexibility associated with mechanical obstruction caused by S. solidus as no significant difference in the ratios of body width (P > 0·05) or depth (P > 0·05) to LS were found between uninfected and infected fish. At a parasite index >0·2, infected fish were unable to perform escape fast-starts increasing the likelihood of predation by their definitive hosts such as loons or belted kingfishers. Three-spined sticklebacks infected with S. solidus with a parasite index of c. 0·2–0·3, however, were compromised by a suite of behavioural (e.g. increased foraging activity and amount of food consumed, increased risk associated with feeding and increased response latency to predatory stimuli), physiological (e.g. increased rate of oxygen consumption, slower growth, delayed sexual maturation and breeding success) and biomechanical (e.g. decreased fast-start performance) factors. Bunodera spp. did not affect the escape fast-start performance of three-spined sticklebacks and no significant difference for maximum velocity (P > 0·05) and maximum acceleration (P > 0·05) was found.
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