Feeding Efficiency by Juvenile Blue Crabs on Two Common Species of Micrograzer Snails

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Coastal Sciences, Gulf Coast Research Laboratory


Juvenile blue crabs, Callinectes sapidus, utilize estuarine seagrass beds as nursery habitat, where they may function as keystone predators. While inhabiting seagrass habitat, juvenile blue crabs consume large numbers of two common micrograzer snails, Bittiolum varium and Astyris lunata; and thus, crab predation may influence the dynamics of these two snails. We compared predator-prey relationships between juvenile blue crabs and the two common micrograzer snails. Based on feeding efficiency criteria, B. varium was more profitable than A. lunata, and the interspecific difference in profitability increased ontogenetically for snails larger than 2 mm in length. Juvenile blue crabs selected B. varium over A. lunata in laboratory feeding trials. The diet preference was also upheld in the field. However, under laboratory conditions, the strength of this preference varied with crab size and season. Medium sized crabs selected B. varium to a greater degree than did small and large crabs. The seasonal effect likely resulted from an interaction between snail species and snail size; with the weaker preference being expressed when B. varium was distributed toward smaller sizes. (C) 2001 Elsevier Science B.V. All rights reserved.

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Journal of Experimental Marine Biology and Ecology





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