Manahan 9420803 Feeding larval forms of benthic marine invertebrates in the cold waters of McMurdo Sound, Antarctica are present in the water column for many months prior to the phytoplankton bloom. It is currently not understood how these feeding larvae of antarctic invertebrates survive long periods under starvation conditions. Knowing the physiological mechanisms of this process is important for understanding the ecology of larvae from antarctic regions. Recent findings with antarctic echinoderm larvae do not support the suggestion that feeding larvae survive this period of negligible phytoplankton abundance by using other food sources (bacteria or dissolved organic material). Physiological data, however, do suggest a possible survival strategy whereby potential larval lifespans can be extended for about one year in the complete absence of food. Such lifespans (without food) for feeding larval forms are unique to antarctic larvae. The metabolism of this process in antarctic echinoderm larvae is the focus of this research. A hypothesis that the metabolic cost of development will be lower in antarctic echinoderms than for the same "unit of differentiation" (fertilized egg to feeding larval form) in comparable temperate larvae will be tested. Such data on temperate larvae already exist and the proposed studies with antarctic larvae will allow for a comparison of stage-specific developmental metabolism. To obtain these metabolic data, a novel technique called coulometric respirometry that permits continuous measurements of metabolic rate during development will be used. In addition, the biochemistry of development will be examined to determine the mechanism(s) of low metabolism in antarctic larvae. Data from experiments will test long-standing hypotheses about cellular mechanisms of low metabolism as they apply to invertebrate development in antarctic environments. The findings from this research may also have implications for larvae developing under lo w food conditions in other cold environments, such as the deep sea.
