INTRASPECIFIC MORPHOLOGICAL VARIABILITY IN MEGALOPAE OF THREE SYMPATRIC SPECIES OF THE GENUS CANCER (BRACHYURA: CANCRIDAE)

Abstract

ABSTRACT Selected morphological traits were documented for megalopae of Cancer magister, C. oregonensis,and C. productus collected at three sites within the Puget Sound basin and at two offshore sites in the eastern Pacific Ocean. Variation in selected traits was compared among species, among individuals within species, and among regions sampled. Traits selected for measurement were those proposed in the literature as diagnostic for identification of species of Cancer. For each of three species of Cancer collected, substantial intraspecific variability in size and appendage setation was documented. Although individual megalopae differed in selected morphological traits from published reports, published values were within the range of those measured in the present study. Significant differences among regions were determined for size and setation in C. magister, with the clearest differences being those between megalopae collected offshore and within the Puget Sound basin. Results indicate that megalopae of C. magister can be separated from those of C. productus and C. oregonensis by size alone, but that the latter two species cannot be separated with certainty on the basis of features described in the literature as diagnostic. Differences between offshore and inland water populations of megalopae of C. magister may reflect hydrographic features of the region and the megalopa's site of origin. Variability in morphological traits must be included in any analysis of factors for species identification and may contribute to analysis of broader ecological issues.