Entrainment of Seasonal Reproductive Cycles in Echinoderms Living Below the Euphotic Zone

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Daylength and other photoperiodic cues regulate reproduction of many animals in shallow-water marine habitats. The depth to which such cues are important in the sea has not been investigated, but it is known that numerous deep-sea and bathyal invertebrates also reproduce seasonally. Seasonal reproduction in these species correlates with numerous potential environmental signals, including seasonal flux of nutrients, but the actual cues that entrain seasonal reproductive cycles have not been investigated experimentally for any deep-sea invertebrate. Using submersibles, Dr. Young will test two potential factors that could control reproduction in bathyal echinoids living on the slope in tropical seas: seasonal flux of macrophytic detritus, and daylength cycles at very low light intensities. He will also investigate the relationship between food supply, growth, fecundity, and timing of reproduction using in situ experiments in which food is manipulated in enclosures on the sea floor.