REIBER, Carl L.: Ontogeny of oxygen sensitivity in crayfish: Peripheral oxygen receptors and cardiorespiratory modulation
Crayfish embryos respond to reductions in water O2 at very early stages of development (stage XII). Heart rate, stroke volume and cardiac output decrease in response to hypoxic exposure at or below 40 mmHg O2 in stage XIII. This response correlates with the critical PO2 value for embryonic metabolism and thus has been attributed to myocardial hypoxia and a reduction in cardiac muscle aerobic capability. Adult crustaceans including crayfish exhibit rapid, transient cardiac and ventilatory responses toward changes in branchial water PO2 mediated by both peripheral and central populations of O2 receptors. Late stage crayfish larvae (stage 3) showed a rapid cardiac and ventilatory response to hyperoxic water exposure, similar to that of adults. Early larval stages (stages 1 & 2) did not exhibit the magnitude or duration of the response toward hyperoxic exposure, which suggests that central receptors may become functional before peripheral O2 receptors. In late embryonic stages (stage XIV) only a minimal cardiac response was observed, indicating that oxygen receptors may not be fully functional until near eclosion. This work was supported by NSF grant IBN-98874534 (C.L.R.)
