The Relationship Between Subunit Composition and O Binding of Blue Crab Hemocyanin.

Hemocyanin-O affinity differs in estuarine and seaside populations of the blue crab Callinectes sapidus. The difference, which is adaptive, is accompanied by different proportions of the six subunits that make up the native hemocyanin polymers. When the hemocyanins are dissociated and separated by alkaline electrophoresis, six subunits can be resolved in most estuarine individuals but two of the six are either present in low concentrations in or absent from most seaside individuals. A third subunit is also variable but the variation is not clearly correlated with locality. O binding measurements of Hcs with the two major wild phenotypes but collected at the same locality reproduce the difference between the natural populations. Measurements on several intermediate phenotypes suggest that the variation of one of the subunits is more important physiologically than variation of the other two.