While most copepods are holoplanktonic, decapod larvae are meroplanktonic with a pelagic larval development ranging from days (Penaeidae) to weeks (most Palaemonidae, Palinuridae). Reproductive strategies result in either the early release of larvae in large numbers of small planktonic forms (Penaeidae) or smaller numbers of advanced larvae after parental incubation (Brachyura, Palaemonidae, Nephropidae, Palinuridae). Commercially-cultured decapod larvae exhibit a wide range of feeding strategies exploiting most of the trophic levels found within the planktonic ecosystem. Studies on these crustacean larvae demonstrate how their digestive physiology is adapted to different feeding strategies during larval development, and provide an insight into the design of appropriate artificial feeds for commercial culture. Comparative measurements of digestive enzyme levels reveal that trypsin-like protease appears to dominate in all larvae investigated. Highest levels occur in herbivorous penaeid and brachyuran larval stages. In contrast, carnivorous lobster and caridean larvae show low protease activity at first feeding and appear to rely upon high-energy digestible live prey for their nutrition. Ontogenetic changes in enzyme type, activity and content are displayed during the penaeid mysis and caridean, brachyuran late zoeal stages as larvae transfer to higher trophic levels. The range and extent of these changes are reviewed for the commercial larval groups of commercially important species. (C) 1997 Elsevier Science B.V.