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alterado para: “Sharks in a changing ocean: a multiscale assessment of anthropogenic pressures on key marine predators”, Sharks Sixth Sense in a Changing Ocean - Effects of Ocean Warming and Acidification on Sharks Electroreception Sixth Sense in a Changing Ocean - Effects of Ocean Warming and Acidification on Sharks Electroreception
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Impact of a simulated marine heatwave in the hematological profile of a temperate shark (Scyliorhinus canicula)
Publication . Pegado, Maria Rita; Santos, Catarina P.; Raffoul, Dayanne; Konieczna, Marta; Sampaio, Eduardo; Luísa Maulvault, Ana; Diniz, Mário; Rosa, Rui; DQ - Departamento de Química; UCIBIO - Applied Molecular Biosciences Unit; LAQV@REQUIMTE; Elsevier
As Earth's temperature continues to rise, sudden warming events, designated as marine heatwaves (MHWs), are becoming more frequent and longer. This phenomenon is already shown to significantly impact marine ecosystems and respective fauna. While experimental acclimation to higher temperatures is known to affect predatory behavior, metabolism and overall fitness of sharks, the effects of short-term exposure to high temperatures on sharks’ physiology has yet to be investigated in a MHW context. Thus, the aim of our work was to study the impact of a category II MHW (Δ3 °C, 15 days) on: i) hematological parameters (total erythrocytes, leukocytes, thrombocytes, erythrocyte nuclear abnormalities (ENAs) counts, and nucleus to cytoplasmic ratio), ii) heart and spleen to body ratios, and iii) ventilation rates of juvenile catsharks (Scyliorhinus canicula). We found that MHW exposure led to significant changes in normal blood cell counts, by lowering erythrocyte counts and nucleus to cytoplasm ratio, and increasing leukocyte and thrombocyte counts. Moreover, ventilation rates increased consistently over the course of the MHW. However, there were no changes regarding the presence of ENA, as well as spleen and heart to body ratios. Our findings indicate limited capabilities for coping with sudden warming events, suggesting potential disruption in shark physiological homeostasis as the frequency, duration and intensity of MHWs are expected to be strengthened.
Impacts of Deoxygenation and Hypoxia on Shark Embryos Anti-Predator Behavior and Oxidative Stress
Publication . Varela, Jaquelino; Martins, Sandra; Court, Melanie; Santos, Catarina Pereira; Paula, José Ricardo; Ferreira, Inês João; Diniz, Mário; Repolho, Tiago; Rosa, Rui; DQ - Departamento de Química; UCIBIO - Applied Molecular Biosciences Unit; LAQV@REQUIMTE; MDPI - Multidisciplinary Digital Publishing Institute
Climate change is leading to the loss of oxygen content in the oceans and endangering the survival of many marine species. Due to sea surface temperature warming and changing circulation, the ocean has become more stratified and is consequently losing its oxygen content. Oviparous elasmobranchs are particularly vulnerable as they lay their eggs in coastal and shallow areas, where they experience significant oscillations in oxygen levels. Here, we investigated the effects of deoxygenation (93% air saturation) and hypoxia (26% air saturation) during a short-term period (six days) on the anti-predator avoidance behavior and physiology (oxidative stress) of small-spotted catshark (Scyliorhinus canicula) embryos. Their survival rate decreased to 88% and 56% under deoxygenation and hypoxia, respectively. The tail beat rates were significantly enhanced in the embryos under hypoxia compared to those exposed to deoxygenation and control conditions, and the freeze response duration showed a significant opposite trend. Yet, at the physiological level, through the analyses of key biomarkers (SOD, CAT, GPx, and GST activities as well as HSP70, Ubiquitin, and MDA levels), we found no evidence of increased oxidative stress and cell damage under hypoxia. Thus, the present findings show that the projected end-of-the-century deoxygenation levels elicit neglectable biological effects on shark embryos. On the other hand, hypoxia causes a high embryo mortality rate. Additionally, hypoxia makes embryos more vulnerable to predators, because the increased tail beat frequency will enhance the release of chemical and physical cues that can be detected by predators. The shortening of the shark freeze response under hypoxia also makes the embryos more prone to predation.
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Fundação para a Ciência e a Tecnologia
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SFRH/BD/117890/2016