The proposed study is part of an ongoing research program on factors that restrict life histories of marine organisms. Among benthic marine animals, alternative modes of reproduction are planktonic dispersed embryos versus protected benthic embryos. Therefore, the presence or absence of benthic embryonic development commonly has consequences for dispersal, recruitment, and mating, with further consequences for the distribution, abundance, and genetics of animals in benthic populations. Benthic egg masses and brood masses vary greatly in form; patterns of variation may convey important information about environmental requirements, but the causes and consequences of this variation are not yet established. Brooding and other forms of protection for benthic development may be limited by embryonic requirements for transfer of oxygen from the surrounding water or the removal from the embryo of diffusible substances to the water. This research will test: (1) dependence of development on supply of oxygen and (2) models of exchange by diffusion or by interstitial flow. Indications of restrictions on development in benthic egg masses and the consequences of these constraints will be examined by comparative and experimental approaches that use representatives of several major groups of benthic marine animals.
