Compensatory growth in threespine sticklebacks (Gasterosteus aculeatus) inhibited by experimental Schistocephalus infections

Compensatory growth responses are made by individual fish to restore their original growth trajectory following a period of growth depression. Little is known about whether diseases impact a fish's capacity for growth compensation. In this study we investigate the effect of Schistocephalus solidus, a common cestode parasite of threespine sticklebacks (Gasterosteus aculeatus), on the ability of host fish to undertake growth compensation following short-term food deprivation. Placebo-infected controls completely compensated for a 2-week deprivation period after 3 weeks postdeprivation feeding, but experimentally infected sticklebacks showed only partial compensation and after 6 weeks of refeeding had attained only 80% of the weight of continually fed infected fish. A major factor limiting the compensatory growth response of infected fish was their reduced hyperphagic response during the period of refeeding. Feed deprivation had no effect on ultimate parasite size of infected fish. We discuss the possible mechanisms limiting hyperphagia in infected fish and consider the fitness implications - for parasites and hosts - of the reduced ability of infected fish to undertake compensatory growth responses.