Parents living in water, embryos developing in air: respiratory adaptations to use both environments in the freshwater gastropod Pomacea figulina (Gastropoda, Ampullariidae)

The ability to use oxygen from both air and water has been considered key to the colonization of terrestrial environments by invertebrates. The freshwater gastropod Pomacea figulina generally lives submerged, although females lay their eggs mainly above water during nighttime, on the stems of aquatic plants, and the embryos develop inside the air-exposed calcareous egg capsules. However, little is known about the physiological adaptations that the ovipositing females and the developing embryos have developed to breathe in air. In this study, we report sexual differences in the aerial and aquatic oxygen consumption of adults and embryonic respiration in aerially developing egg clusters. We found that the males and females of this species can obtain oxygen from both water and air, although uptake rates for both sexes were much lower in air than in water. Females in air consumed oxygen 42% faster than males, which may be related with the habit of egg laying above water level. Developing embryos inside calcareous eggs obtained oxygen faster when submersed under water than when exposed to air, although embryos near hatching were better able to use oxygen from both air and water than embryos at earlier stages of development. Our data suggest that for P. figulina, laying eggs in the terrestrial environment may be more a strategy for protecting embryos from predators than a respiratory adaptation.