Allozyme Variation, Developmental Rate, and Differential Mortality in the Teleost Fundulus heteroclitus

Abstract

Developing embryos of Fundulus heteroclitus were incubated at three temperatures and three salinities until hatching. Each fry was scored for lactate dehydrogenase-B (LDH-B), malate dehydrogenase-A (MDH-A), glucose phosphate isomerase-B (GPI-B), and phosphoglucomutase-A (PGM-A) phenotype. Signiicant correlations with hatching time were found among single- and multiple-locus phenotypes at all four loci At 20° C the multilocus effects were generally additive, but the interaction between MDH-A/GPI-B dilocusphenotypes was synergistic. Temperatures above or below 20° C minimized these effects. Phenotype-specific mortality at high temperatures (30° C) was significant in both single and dilocus phenotypes. In general, phenotypes most common to high latitudes were most susceptible to heat stress. A negative correlation was observed between heterozygosity and hatching time at 20° C and 33‰ salinity. The basis of this correlation appeared to be a function of the proportion of individuals having single and dilocus slow-hatching homozygous phenotypes in each category. These proportions were largely determined by the allele frequencies in the population.