Hemoglobin heterogeneity in two species of commercial fish, the croaker and spot

The croaker (Micropogon undulatus) and spot (Leiostomus xanthurus) are closely related to each other and commercially utilized as industrial bottom fish. This study was begun to determine whether these species exist as genetically different and reproductively isolated subpopulations or as one freely interbreeding population. Polyacrylamide gel electrophoresis of CO-hemoglobin (CO-Hb) from fifty individaul croakers reveal three phenotypes occur in Galveston Bay. Patterns of croaker CO-Hb show multiple bands, whereas those of spot CO-Hb show no individual variation and only two components. Sedimentation analysis of croaker CO-Hb shows one component (s[lowered 20,w]=4.3S) and indication of dissociation in presence of acid, base, and strong salts. Globin prepared by acid-acetone precipitation and fractionated on CM-cellulose with urea-mercapto-ethanol-phosphate buffer gave three or four fractions. Resolution is poor and a better fractionation procedure is required to separate globins of croaker. These and other results indicate that in croaker genetic polymorphism exists, and at least three sub-populations occur.