UC Davis

The ability of 11 species of planktonic and benthic invertebrates to prey on larvae of two estuarine species of crabs was determined in the laboratory. Ten of 11 of these predators with diverse feeding modes consumed crab larvae. Two of three planktonic invertebrates tested ate more larvae of the fiddler crab, Uca minax (LeConte, 1855), than larvae of the mud crab, Rhithropanopeus harrisii (Gould, 1841), and 4 of 8 benthic invertebrates consumed more U. minax larvae. None of the invertebrates ingested more R. harrisii than U. minax larvae. The larger size of R. harrisii larvae rather than their longer spines likely deterred most invertebrates, although differences in swimming speed, avoidance behavior or penetrability of the exoskeleton also may account for the differential predation on the two species. Available information on the distribution, abundance and feeding habits of potential predators of crab larvae was reviewed and synthesized with results of this study to determine if dispersal patterns of estuarine crabs likely have evolved in response to predictable trends in predation by invertebrates. Preliminary evidence for this hypothesis is equivocal but suggests that particular taxa of hydromedusae are more likely to influence dispersal of estuarine crabs than are other planktonic and benthic invertebrates. © 1992.