Clinal variation in the specific activity of lactate dehydrogenase‐B

LDH‐B 4 specific activity was determined from Fundulus heteroclitus collected in the field and from laboratory‐acclimated fish from four latitudinally distinct populations. The differences in the enzyme activity between populations for both field‐caught and laboratory‐acclimated fish are significant, with the northern populations having the highest LDH‐B 4 enzyme activity. This clinal variation in enzyme activity is consistent with an evolutionary mechanism that compensates for lower environmental temperatures in colder northern latitudes.