REITZEL, A.M.; MINER, B.G.: Spawning Times and the Importance of Development Time in Life History Models of Marine Invertebrates

Trade-offs between fecundity and development time have been used in life history models to predict the optimal amount of maternal energy to supply eggs. However, there is very little evidence to support that selection favors shorter development time. Other factors like juvenile fitness, exogenous food, larval transport, and fertilization success may influence the evolution of life history and maternal reserves. Here we indirectly test the importance of development time on spawning season. In particular, we look at spawning times in species of marine invertebrates with lecithotrophic larvae (non-feeding). We assume species with lecithotrophic larvae will be more flexible in the time in which they can spawn, since larvae can develop when food is present or not. Additionally, without the need to feed, temperature will most influence development time. We therefore predict that species that produce lecithotrophic larvae will spawn just prior to the warmest seasonal seawater temperatures. However, other selective pressures may be important if lecithotrophic larvae develop during colder months. We surveyed spawning times for species with planktotrophic (feeding), lecithotrophic, and brooded larvae from the Pacific Northwest. Water temperatures for ten years were compared to spawning times to test our prediction. Species with planktotrophic larvae typically spawned throughout spring and summer. Species with lecithotrophic larvae were mostly restricted to the months June through August, with the exception of annelids. Species with brooded larvae were typically found to brood year around. Water temperatures and spawning time did not match the prediction that development time influences spawning times and are not consistent with the theoretical model’s parameters.