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- Deficit in digestive capabilities of bamboo shark early stages under climate changePublication . Rosa, Rui; Pimentel, Marta; Galan, Juan; Baptista, Miguel; Lopes, Vanessa M.; Couto, Ana; Guerreiro, Miguel; Sampaio, Eduardo; Castro, Joana; Santos, Catarina; Calado, Ricardo; Repolho, TiagoLittle empirical information is currently available on the potential effects of acidification and/or warming in sharks, but none exist about digestive capabilities under such future conditions. Here, we investigated the impact of both acidification (ΔpH = 0.5) and warming (+4; 30 °C) on the digestive enzyme levels of recently hatched tropical bamboo shark (Chiloscyllium punctatum). Thirty days post-hatching, juvenile sharks revealed a significant increase in pancreatic trypsin levels under warming, but also a significant decrease under acidification, namely a 42 % drop under present-day temperature and 44 % drop under the warming condition. A similar trend was recorded for the alkaline phosphatase activity in shark’s intestine, i.e. the impact of environmental hypercapnia was also quite notorious—a 50 % drop under present-day temperature and 49 % drop under the warming condition. Thus, our present findings suggest that acidification and warming acted antagonistically, leading to similar enzyme activities under present and future conditions. Future directions on this topic of research should point towards the study of other types of sharks, namely pelagic ones with quite higher energetic demands.
- Absence of cellular damage in tropical newly hatched sharks (Chiloscyllium plagiosum) under ocean acidification conditionsPublication . Lopes, Ana Rita; Sampaio, Eduardo; Santos, Catarina; Couto, Ana; Pegado, Maria Rita; Diniz, Mário S.; Munday, Philip L.; Rummer, Jodie L.; Rosa, RuiSharks 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.