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

Abstract

24Assessment of stress from varied sources are usually evaluated on individuals derived from a 25 single population, and are assumed to represent all populations of that species. However, recent 26 research has identified intraspecies variations in the stress response, which may be mediated by 27 life history. We examined how life history can influence the physiological responses to an acute 28 stress event by evaluating sea lamprey (Petromyzon marinus) parasitism response in two lake 29 trout (Salvelinus namaycush) morphotypes-the lean and siscowet. The morphotypes differ such 30 that the lean grows faster, is more fecund, and has a shorter life span. In contrast the siscowet 31 grows slower, is older at maturity, and lives longer. Our study compared long-term parasitism 32 responses between wild leans and siscowets in Lake Superior and immediate responses in 33 laboratory parasitism trials using lake trout reared under common environmental conditions. 34Leans, but not siscowets, showed changes in steroid binding protein function, and weak evidence 35 of parasitism gigantism in response to parasitism. Both morphotypes showed indications of 36 reproductive endocrine alterations in response to parasitism. Our results demonstrate intraspecies 37 variation in physiological stressor response, which is mediated by life history differences that 38 could potentially have differential population implications. 39 40 41 42 43 44 45 46

Sea lampreys elicit strong transcriptomic responses in the lake trout liver during parasitism

“…None of these pathways were observed to be regulated in parasitized leans. It appears that in the wild, siscowets are parasitized at a higher rate and more intensely than leans [ 24 ]. While there could be several reasons for this difference, the high lipid levels in siscowets may make them more capable energetically of sustaining lamprey parasitism events.…”

“…Lake trout and sea lamprey final weights were recorded to aid standardization of parasitism events. The number and type of sea lamprey wounds on the lake trout were characterized and blood and gonad samples were taken for physiological analyses described separately [ 24 ]. A liver sample was taken from each fish and flash frozen on dry ice and stored at −80 °C until RNA extraction.…”

“…In the current study, lean and siscowet lake trout that have been reared in the hatchery from eggs to adults under identical environmental conditions [ 22 ] were used for controlled lamprey parasitism experiments in the lab. Endocrine and bioenergetic changes in relation to the lamprey parasitism on the hatchery-reared lake trout morphotypes have been presented separately [ 24 ]. Here we describe the changes in the hepatic transcriptome of lean and siscowet lake trout following lamprey parasitism.…”

The Influence of Life History on the Response to Parasitism: Differential Response to Non-Lethal Sea Lamprey Parasitism by Two Lake Charr Ecomorphs

“…However, little is known about lake charr that survive sea lamprey parasitism. In the short-term, sea lamprey parasitism alters host lake charr plasma sex steroid concentrations ( Smith et al 2016 ), blood chemistry ( Edsall and Swink 2001 ), plasma protein expression ( Bullingham et al 2021 ), and transcriptional regulation of genes involved in inflammation, cellular damage, and energy utilization ( Goetz et al 2016 ). In the longer term, parasitism influences expression of proteins related to immune response, lipid transport, and blood coagulation ( Bullingham et al 2021 ).…”

“…It is possible that these health repercussions could lead to a diversion of energy from normal physiological processes such as growth, immune function, and reproduction, and have long-term implications. Furthermore, the response to parasitism may vary depending on the life history characteristics of the lake charr ecomorph that has been parasitized ( Smith et al 2016 ).…”