Integumental nutrient uptake by aquatic organisms.

Integumental nutrient transport is a widespread characteristic of soft-bodied marine invertebrates. These processes, which are qualitatively similar to the Na-dependent transporters of intestinal epithelia, have kinetic and energetic characteristics that make them particularly well suited for accumulating materials from the extremely low substrate concentrations found in seawater. Despite the low concentrations of DOM in natural waters, rates of DOM uptake are large and clearly capable of supporting a significant fraction of the metabolic needs of some species. Indeed, recent studies with larval invertebrates suggest that integumental uptake of DOM may play a pivotal role in animal nutrition. Current and future studies on the mechanism and regulation of these processes, on the metabolic fate of accumulated DOM, and on the distribution of DOM in natural waters, promise to resolve the remaining issues on the role of integumental transport in the nutrition of aquatic organisms.