Phenotypic variation and lability of the subunit composition of the hemocyanin of Uca pugilator

Abstract

The monomeric subunit composition of the hemocyanin of the sand fiddler crab Uca pugilator was examined in six samples totalling 342 individuals and representing latitudinal and salinity gradients. A total of 12 different polypeptide chains were separated electrophoretically, of which as few as four and as many as nine were present in an individual. The small quantities of several chains suggest a mixed population of the predominantly 2×6 aggregates in the blood. There was no effect of sex and no clear effect of salinity. Samples of populations found near the northern and southern limits of the species, however, were very different from each other and also from samples of populations in the middle of the geographic range. Specifically, samples from the geographic limits exhibit far less variation than those from the middle of the species range. Only one group of three minor chains clearly varies as if they might be encoded at the same locus. Moreover, the condition of most of the monomers, including those three as well as several of the major chains, is not genetically fixed in the adult stage.