Thermal tolerance and hypoxia tolerance are associated in blacktip reef shark ( Carcharhinus melanopterus ) neonates - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Experimental Biology Année : 2020

Thermal tolerance and hypoxia tolerance are associated in blacktip reef shark ( Carcharhinus melanopterus ) neonates

Ian Bouyoucos
Phillip Morrison
Ornella Weideli
Eva Jacquesson
  • Fonction : Auteur
Colin Simpfendorfer
Colin Brauner
  • Fonction : Auteur
Jodie Rummer

Résumé

ABSTRACT Thermal dependence of growth and metabolism can influence thermal preference and tolerance in marine ectotherms, including threatened and data-deficient species. Here, we quantified the thermal dependence of physiological performance in neonates of a tropical shark species (blacktip reef shark, Carcharhinus melanopterus) from shallow, nearshore habitats. We measured minimum and maximum oxygen uptake rates (ṀO2), calculated aerobic scope, excess post-exercise oxygen consumption and recovery from exercise, and measured critical thermal maxima (CTmax), thermal safety margins, hypoxia tolerance, specific growth rates, body condition and food conversion efficiencies at two ecologically relevant acclimation temperatures (28 and 31°C). Owing to high post-exercise mortality, a third acclimation temperature (33°C) was not investigated further. Acclimation temperature did not affect ṀO2 or growth, but CTmax and hypoxia tolerance were greatest at 31°C and positively associated. We also quantified in vitro temperature (25, 30 and 35°C) and pH effects on haemoglobin–oxygen (Hb–O2) affinity of wild-caught, non-acclimated sharks. As expected, Hb–O2 affinity decreased with increasing temperatures, but pH effects observed at 30°C were absent at 25 and 35°C. Finally, we logged body temperatures of free-ranging sharks and determined that C. melanopterus neonates avoided 31°C in situ. We conclude that C. melanopterus neonates demonstrate minimal thermal dependence of whole-organism physiological performance across a seasonal temperature range and may use behaviour to avoid unfavourable environmental temperatures. The association between thermal tolerance and hypoxia tolerance suggests a common mechanism warranting further investigation. Future research should explore the consequences of ocean warming, especially in nearshore, tropical species.

Dates et versions

hal-03368799 , version 1 (07-10-2021)

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Citer

Ian Bouyoucos, Phillip Morrison, Ornella Weideli, Eva Jacquesson, Serge Planes, et al.. Thermal tolerance and hypoxia tolerance are associated in blacktip reef shark ( Carcharhinus melanopterus ) neonates. Journal of Experimental Biology, 2020, 223 (14), ⟨10.1242/jeb.221937⟩. ⟨hal-03368799⟩
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