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We investigated the morpho-functional relationships underlying shell use and the role of shells as a resource in Pagurus prideaux and Paguristes eremita, collected along a bathymetric cline in the Sicilian Channel (southern Italy). These relationships were influenced by the presence of epibiont anemones, which colonize gastropod shells inhabited by hermit crabs. Sea-anemones appeared to play a different role in the shell use of the two species of crabs. In P.prideaux, relationships with Adamsia palliata determined the use of globose shells (mainly Naticidae with a height/width ratio <1) and of small and damaged shells; in this case, the shell primarily played the role of a substrate for the settlement of anemones, and consequently its inhabiting and protective function tended to become less important. In P.eremita, relationships with the anemone Calliactis sp. and tube dwelling epibionts are correlated with the use of large, heavy shells with respect to the size of the crabs and also of well conserved shells; these shells offer an extensive surface for anemone settlement. In this case, the shell played a double role: an inhabiting-protective resource for the crab as well as a substrate for the anemone. Further experimental work will aim at testing these hypotheses, in an attempt at validating the proposed models and explaining the observed patterns. [ABSTRACT FROM AUTHOR]