Influence of seasonal environmental variation on the reproduction of four tropical marine gastropods

摘要

The 2 main hypotheses put forward to explain seasonal timing of marine invertebrate reproduction hinge on variation in temperature and phytoplankton. Seasonal upwelling in the tropical eastern Pacific provides an ideal system in which to test these ideas. During the non-upwelling season, the Bay of Panama is warmer, less saline and less productive than during the upwelling season. We followed egg deposition of 4 intertidal gastropod species-Littoraria variegata, Cerithideopsis californica var. valida, Crepidula cf. marginalis and Natica chemnitzi-to determine if these seasonal environmental differences are associated with variation in reproductive intensity or offspring size. The species from the mangroves, L. variegata and C. californica, produced fewer egg masses during the dry season. The slipper limpet C. cf. marginalis was more likely to brood during the dry season. Egg masses from the moon snail N. chemnitzi showed no difference in abundance between the seasons. Shell length at hatching, an estimate of per offspring maternal investment, was larger during the dry season for C. californica and C. cf. marginalis but did not differ across the seasons for L. variegata. Hatching size in the moon snail was bimodal during the dry season, but both offspring size classes showed increased offspring size in the dry season compared to the wet season. Three of the 4 species show patterns in offspring size consistent with the offspring temperature-size rule, while seasonal cycles in reproductive intensity are likely driven by other factors such as adult food availability or desiccation stress.