Faced with environmental stress, the females of many marine invertebrate species can
isolate their brood chambers from the external environment for prolonged periods. Although brood
chambers have therefore typically been assumed to protect the brooded embryos, the effects of
continued isolation on conditions within brood chambers have not been examined. In the present
research, we investigated the effects of external stress on conditions in the brood chambers for 2
sympatric species, the gastropod Crepipatella dilatata and the bivalve Ostrea chilensis. Both species
incubate their embryos in the pallial cavity for at least 4 wk before the young emerge as larvae
(oyster) or juveniles (gastropod). Brooding and non-brooding females were stimulated to isolate the
pallial cavity from the external environment by exposing them to water of reduced salinity (