<b>Thermal acclimation and its reversal in early life stages of brook trout</b>

In juvenile and adult fishes, the initiation, completion, and reversal of acclimation have been studied but there are few data on the dynamics of acclimation in early life stages. We examined how chronic warming during incubation altered thermal tolerance in early life stages of brook trout (<i>Salvelinus fontinalis</i>) to quantify the scope and duration of thermal acclimation and carryover effects during early development. We assessed how quickly the acclimation of upper thermal tolerance (CT_max) was lost once hatched larvae were moved to common conditions. In embryos, and four weeks after hatch, fish in warmer treatments had a positive acclimation response (higher CT_max). Eight weeks after hatch, acclimation was completely reversed, whereby fry that had been reared in ambient (cooler) conditions had higher thermal tolerance than those from warm treatments. Early life stages of brook trout can acclimate their thermal tolerance throughout development but acclimation to warmer temperatures can have a cost in the form of lower body condition.

针对幼鱼和成鱼，其热驯化（thermal acclimation）的启动、完成与逆转过程已有诸多研究，但针对早期生命阶段热驯化动力学的相关数据仍较为匮乏。本研究以溪红点鲑（*Salvelinus fontinalis*）为研究对象，探究了孵化期慢性升温对其早期生命阶段热耐受性的影响，旨在量化热驯化的作用范围与持续时长，以及早期发育过程中的遗留效应。同时，我们还评估了孵化幼体被转移至常规环境后，其高温热耐受性（以临界热极限CT_max为指标）的驯化效应消退速率。在胚胎阶段及孵化后4周时，经升温处理的个体呈现出正向热驯化响应，其临界热极限CT_max更高。孵化后8周时，热驯化效应完全逆转：即在常温（较低温）环境中培育的幼鱼，其热耐受性反而高于经升温处理的个体。溪红点鲑的早期生命阶段可在整个发育过程中对其热耐受性进行驯化，但对升温环境的驯化会以身体状况下降的形式产生适应代价。