Absence of cellular damage in tropical newly hatched sharks (Chiloscyllium plagiosum) under ocean acidification conditions
Sharks have maintained a key role in marine food webs for 400 million years and across varying physicochemical contexts, suggesting plasticity to environmental change. In this study, we investigated the biochemical effects of ocean acidification (OA) levels predicted for 2100 (pCO2 ~ 900 μatm) on newly hatched tropical whitespotted bamboo sharks (Chiloscyllium plagiosum). Specifically, we measured lipid, protein, and DNA damage levels, as well as changes in the activity of antioxidant enzymes and non-enzymatic ROS scavengers in juvenile sharks exposed to elevated CO2 for 50 days following hatching. Moreover, we also assessed the secondary oxidative stress response, i.e., heat shock response and ubiquitin levels. Newly hatched sharks appear to cope with OA-related stress through a range of tissue-specific biochemical strategies, specifically through the action of antioxidant enzymatic compounds. Our findings suggest that ROS-scavenging molecules, rather than complex enzymatic proteins, provide an effective defense mechanism in dealing with OA-elicited ROS formation. We argue that sharks’ ancient antioxidant system, strongly based on non-enzymatic antioxidants (e.g., urea), may provide them with resilience towards OA, potentially beyond the tolerance of more recently evolved species, i.e., teleosts. Nevertheless, previous research has provided evidence of detrimental effects of OA (interacting with other climate-related stressors) on some aspects of shark biology. Moreover, given that long-term acclimation and adaptive potential to rapid environmental changes are yet experimentally unaccounted for, future research is warranted to accurately predict shark physiological performance under future ocean conditions.
KeywordsCarbon dioxide CO2 Elasmobranchs Antioxidant systems Heat shock response Oxidative damage
We would like to thank Eduarda Pinto for the fundamental technical support during the preparation of the experimental setup and shark acclimation.
The Portuguese Foundation for Science and Technology (FCT) supported this work through the project grant PTDC/AAG-GLO/1926/2014 and Programa Investigador FCT 2013 to R.R. FCT also supported this work through (i) the strategic project UID/MAR/04292/2013 granted to MARE and (ii) PhD grants to ARL (SFRH/BD/97070/2013), ES (SFRH/BD/131771/2017), CS (SFRH/BD/117890/2016), and MRP (SFRH/BD/111691/2015). Both PLM and JLR are supported by funding from the Australian Research Council (ARC) Centre of Excellence for Coral Reef Studies.
Compliance with ethical standards
Competing of interests
The authors declare that they have no conflicts of interest.
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