Miriam Fernández1, Simone Baldanzi2
1Pontificia Universidad Católica de Chile, Chile - 2Universidad de Valparaíso, Chile
The influence of globally changing environmental stressors (e.g., temperature, hypoxia) on the reproductive patterns of species that aggregate embryos is poorly understood, particularly in coastal reefs along upwelling zones. These species are particularly interesting, considering evidence suggesting that restrictions in oxygen provision to embryo aggregations could explain the association between small body size and brooding among marine invertebrates. Brachyuran crabs are an exception to the rule, and therefore serve as a good model for studying the effect of body size and environmental variables on constraints to oxygen provision to embryos. Using studies conducted over 20 years, the patterns of female behavior (abdominal flapping frequency), oxygen availability in embryo masses, and metabolic incubation cost were analyzed by (a) comparing three species of contrasting body size: Pisoides edwardsi (11.7+0.9 mm), Acanthocyclus gayi (21.2+2.1 mm) and Romaleon setosus (124.1+10.1 mm), all inhabiting coastal reefs, (b) evaluating the influence of temperature (10, 14, and 18°C) and hypoxia (10 and 100% air saturation) on the largest body-size species. All species exhibited the same oxygen provision behavior (abdominal flapping), but the frequency increased 5.5 times with body size. Nevertheless, embryos from the larger body-sized species experienced within-clutch hypoxic conditions five times longer than those of the smaller body-sized species, in spite doubling the metabolic cost associated with oxygen provisioning. Temperature and hypoxia strongly influenced flapping frequency, embryo exposure to hypoxia, and metabolic costs of brooding. Mean abdominal flapping increased five times under hypoxia and temperature significantly affected flapping frequency and metabolic costs associated with oxygen provision behaviors (a five-fold increase across body size for both variables). The results suggest that both environmental variables changing globally might be important determinants of the reproductive patterns of Brachyuran crabs and life history patterns of marine invertebrates.