Abstract
Seawater pH lowering, known as ocean acidification, is considered among the major threats to marine environment. In this study, post-spawning adults of the sea urchin Paracentrotus lividus were maintained at three pH values (8.0, 7.7, 7.4) for 60 days. Physiological, biochemical, cellular, behavioural and reproductive responses were evaluated in males and females. Significant differences between sexes were observed, with higher ammonia excretion and lower catalase activity in males. Respiration rate (after 21 days), catalase activity in gonads and total coelomocyte count showed the same increasing trend in males and females under low pH. Ammonia excretion, gonadosomatic index and lysozyme activity exhibited opposite responses to low pH, with an increasing trend in males and decreasing in females. Results demonstrated that exposure to low pH could result in different response strategies of male and female sea urchins at a physiological, biochemical and immunological level. Reduced female gonadosomatic index under low pH suggested decreased energy investment in reproduction.
Highlights
Ocean acidification (OA) is a phenomenon of lowering seawater pH, due to the dissolution of rising atmospheric CO2
When exposed to OA, organisms may change their resource energy allocation and due to higher production cost of eggs compared to sperm, females could be deemed more vulnerable to this stressor
No effects of the experimental conditions tested were recorded in respiration rate after 7 and 40 days of exposure (Fig. 1a, Table 2)
Summary
Ocean acidification (OA) is a phenomenon of lowering seawater pH, due to the dissolution of rising atmospheric CO2. Responses to OA represent a species-specific phenomenon, and the effects detected in laboratory experiments are dependent on geographic area and life-history stages of the studied species (Hall-Spencer et al 2015), as well as on the duration of the experimental exposure (Suckling et al 2015). Notwithstanding, Ellis et al (2017) reported in their review that only 3.77% of 511 OA studies published between January 2008 and May 2016 tested gender-related responses in fish, crustaceans, echinoderms and molluscs. Sex significantly influenced the response to OA, suggesting that sex has to be considered in order to correctly evaluate the impact at the population level (Ellis et al 2017)
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