ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia.
ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia.
J Therm Biol. 2020 May;90:102582. doi: 10.1016/j.jtherbio.2020.102582. Epub 2020 Apr 4.
Marine ectotherms are often sensitive to thermal stress, and certain life stages can be particularly vulnerable (e.g., larvae or spawners). In this study, we investigated the critical thermal maxima (CT) of larval and early juvenile life stages of three tropical marine fishes (Acanthochromis polyacanthus, Amphiprion melanopus, and Lates calcarifer). We tested for potential effects of developmental acclimation, life stage, and experimental heating rates, and we measured metabolic enzyme activities from aerobic (citrate synthase, CS) and anaerobic pathways (lactate dehydrogenase, LDH). A slightly elevated rearing temperature neither influenced CT nor CS activity, which otherwise could have indicated thermal acclimation. However, we found CT to either remain stable (Acanthrochromis polyacanthus) or increase with body mass during early ontogeny (Amphiprion melanopus and Lates calcarifer). In all three species, faster heating rates lead to higher CT. Acute temperature stress did not change CS or LDH activities, suggesting that overall aerobic and anaerobic metabolism remained stable. Lates calcarifer, a catadromous species that migrates from oceanic to riverine habitats upon metamorphosis, had higher CT than the two coral reef fish species. We highlight that, for obtaining conservative estimates of a fish species' upper thermal limits, several developmental stages and body mass ranges should be examined. Moreover, upper thermal limits should be assessed using standardized heating rates. This will not only benefit comparative approaches but also aid in assessing geographic (re-) distributions and climate change sensitivity of marine fishes.
海洋变温动物通常对热应激敏感，某些生命阶段尤其脆弱（例如幼虫或产卵期个体）。在这项研究中，我们调查了三种热带海洋鱼类（Acanthochromis polyacanthus、Amphiprion melanopus 和 Lates calcarifer）的幼虫和早期幼鱼阶段的临界热极值（CT）。我们检验了发育驯化、生命阶段和实验加热率的潜在影响，并测量了来自有氧（柠檬酸合酶，CS）和无氧途径（乳酸脱氢酶，LDH）的代谢酶活性。略微升高的养殖温度既没有影响 CT 也没有影响 CS 活性，否则这可能表明了热驯化。然而，我们发现 CT 要么保持稳定（Acanthrochromis polyacanthus），要么在早期发育过程中随着体重增加（Amphiprion melanopus 和 Lates calcarifer）。在所有三种鱼类中，更快的加热率导致更高的 CT。急性温度应激并未改变 CS 或 LDH 活性，这表明整体有氧和无氧代谢仍然稳定。Lates calcarifer 是一种洄游鱼类，在变态后从海洋洄游到河流栖息地，其 CT 高于两种珊瑚礁鱼类。我们强调，为了获得鱼类物种最高热限的保守估计，应该检查几个发育阶段和体重范围。此外，应该使用标准化的加热率来评估最高热限。这不仅将有益于比较方法，还有助于评估海洋鱼类的地理（再）分布和气候变化敏感性。
