Faced with environmental stress, the females of many marine invertebrate species canisolate their brood chambers from the external environment for prolonged periods. Although broodchambers have therefore typically been assumed to protect the brooded embryos, the effects ofcontinued isolation on conditions within brood chambers have not been examined. In the presentresearch, we investigated the effects of external stress on conditions in the brood chambers for 2sympatric species, the gastropod Crepipatella dilatata and the bivalve Ostrea chilensis. Both speciesincubate 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 thepallial cavity from the external environment by exposing them to water of reduced salinity (<22 to24 psu). We then recorded subsequent changes in salinity, dissolved oxygen, pH, and ammonium ionconcentration within the pallial fluid. Although salinity within the pallial cavity remained high forboth species, oxygen availability for brooding females of C. dilatata and O. chilensis dropped tohypoxic levels (<1.5 mg O2 l–1) within 12 h and 20 min, respectively. In addition, pH of the intrapallialfluid dropped substantially with prolonged maternal isolation, suggesting a possible impact onshell formation for brooded veligers. Indeed, in the case of C. dilatata, the pH of pallial fluid initiallyfell to 6.4, but then tended to become more basic after 6 h of maternal isolation, a possible consequenceof shell dissolution. On the other hand, ammonium ion concentration increased progressivelywith prolonged maternal isolation. Our data show that, whereas initially the isolation mechanismprotected incubated embryos from exposure to low salinity stress, continued isolation from theexterior transformed the brood cavity from a protective environment to an oppressive one, i.e. from aprotective nursery to more of a prison
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