Wheeler Carolyn R, Lang Bethan J, Mandelman John W, Rummer Jodie L
ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4814, Australia.
School for the Environment, The University of Massachusetts Boston, Boston, MA 02125, USA.
Conserv Physiol. 2022 Dec 28;10(1):coac074. doi: 10.1093/conphys/coac074. eCollection 2022.
Owing to climate change, most notably the increasing frequency of marine heatwaves and long-term ocean warming, better elucidating the upper thermal limits of marine fishes is important for predicting the future of species and populations. The critical thermal maximum (CT), or the highest temperature a species can tolerate, is a physiological metric that is used to establish upper thermal limits. Among marine organisms, this metric is commonly assessed in bony fishes but less so in other taxonomic groups, such as elasmobranchs (subclass of sharks, rays and skates), where only thermal acclimation effects on CT have been assessed. Herein, we tested whether three life history stages, sex and body size affected CT in a tropical elasmobranch, the epaulette shark (), collected from the reef flats surrounding Heron Island, Australia. Overall, we found no difference in CT between life history stages, sexes or across a range of body sizes. Findings from this research suggest that the energetically costly processes (i.e. growth, maturation and reproduction) associated with the life history stages occupying these tropical reef flats do not change overall acute thermal tolerance. However, it is important to note that neither embryos developing , neonates, nor females actively encapsulating egg cases were observed in or collected from the reef flats. Overall, our findings provide the first evidence in an elasmobranch that upper thermal tolerance is not impacted by life history stage or size. This information will help to improve our understanding of how anthropogenic climate change may (or may not) disproportionally affect particular life stages and, as such, where additional conservation and management actions may be required.
由于气候变化，尤其是海洋热浪频率增加和海洋长期变暖，更好地阐明海洋鱼类的热上限对于预测物种和种群的未来至关重要。临界热最大值（CT），即物种能够耐受的最高温度，是一种用于确定热上限的生理指标。在海洋生物中，该指标通常在硬骨鱼类中进行评估，但在其他分类类群中评估较少，例如板鳃亚类（鲨鱼、鳐鱼和魟的亚纲），在这类生物中仅评估了热驯化对CT的影响。在此，我们测试了三个生活史阶段、性别和体型是否会影响从澳大利亚赫伦岛周围礁坪采集的热带板鳃亚类肩章鲨的CT。总体而言，我们发现生活史阶段、性别或不同体型之间的CT没有差异。这项研究的结果表明，与占据这些热带礁坪的生活史阶段相关的能量消耗巨大的过程（即生长、成熟和繁殖）不会改变整体急性热耐受性。然而，需要注意的是，在礁坪中未观察到或采集到正在发育的胚胎、新生幼体，也没有采集到正在积极包裹卵鞘的雌性个体。总体而言，我们的研究结果首次在板鳃亚类生物中证明，热耐受性上限不受生活史阶段或体型的影响。这些信息将有助于增进我们对人为气候变化如何（或是否）不成比例地影响特定生活阶段的理解，以及因此在哪些方面可能需要采取额外的保护和管理行动。
