Differential physiological response to sea lamprey parasitism between lake trout (Salvelinus namaycush) morphotypes from Lake Superior

Abstract

Assessment of stress from varied sources is usually evaluated using individuals derived from a single population and is assumed to represent all populations of that species. However, recent research has identified intraspecies variations in the stress response, which may be mediated by life history. We examined how life history can influence the physiological responses to an acute stress event by evaluating sea lamprey (Petromyzon marinus) parasitism response in two lake trout (Salvelinus namaycush) morphotypes: the lean and the siscowet. The morphotypes differ in that the lean grows faster, is more fecund, and has a shorter life span. In contrast, the siscowet grows slower, is older at maturity, and lives longer. Our study compared long-term parasitism responses between wild leans and siscowets in Lake Superior and immediate responses in laboratory parasitism trials using lake trout reared under common environmental conditions. Leans, but not siscowets, showed changes in steroid-binding protein function and weak evidence of gigantism in response to parasitism. Both morphotypes showed indications of reproductive endocrine alterations in response to parasitism. Our results demonstrate intraspecies variation in physiological stressor response, which is mediated by life history differences that could potentially have differential population implications.