Interaction between reduced pH and multiple stressors affects the physiology of the fiddler crab Leptuca thayeri (Rathbun, 1900) (Decapoda: Brachyura: Ocypodidae)

Abstract

Increasing ocean acidification combined with other impacts may cause changes in homeostatic mechanisms of intertidal invertebrates. Stressors do not act in isolation, and experimental work is needed to assess their synergistic potential. We evaluated the effect of exposure to multiple stressors on the survival, osmoregulation, metabolism, Q10, excretion, hepatosomatic index, and energy substrate oxidation on of the fiddler crab Leptuca thayeri (Rathbun, 1900). Crabs were exposed to two pH values (7.0, 6.3) combined with temperatures (20, 25, 30, 35, 40 °C) and these pH values combined with salinities (10, 20, 30, 40, and 50 psu) during acute exposure. All individuals died at 40 °C. Crabs osmoregulated, suggesting that the factors evaluated did not affect salt absorption or secretion. Individuals were weak hyperosmorregulators at lower salinities in the pH 7 control, but they became strong hyperosmoregulators at acidified pH 6.3. Alterations in oxygen consumption and hepatosomatic index were observed in individuals exposed to the acidified pH combined with temperatures or salinities, compared to those kept in the control pH. Q10 was elevated under an acidified pH, with crabs using proteins and lipids as energy substrates. The interaction between reduced pH and temperature or salinity thus affected physiological mechanisms related to the energetic metabolism, but elevated temperatures are more limiting because they affected survival. These physiological effects of acute exposure offer clues about extreme climatic events, which have a short duration but can affect the related energy demands.