VARIATION IN GENETIC-TRAITS OF THE LUGWORM ARENICOLA-MARINA - TEMPERATURE-RELATED EXPRESSION OF MITOCHONDRIAL ALLOZYMES

Genetic traits of the lugworm Arenicola marina were determined for 4 A tlantic populations from France to Norway and compared with a populati on from the sub-arctic White Sea in Russia. Seven loci were analysed u sing horizontal starch gel electrophoresis. A low heterozygosity (0.09 to 0.17) and a non-significant heterozygote deficiency were found in all populations. The genetic identity between lugworms of European Atl antic populations was high, whereas similarity of the Atlantic populat ions with the population from the White Sea was low. The gene flow bet ween the Atlantic and the White Sea populations must be considered neg ligible, as deduced from the average high and significant gene differe ntiation F-ST. In particular, differences in allele frequencies of glu cose phosphate isomerase (Gpi) and phosphoglucomutase (Pgm) showed tha t the White Sea population differed significantly from the others. A v ery strong correlation existed between the frequency of the alleles of isocitrate dehydrogenases 2-A and -B (Idh2-A and Idh2-B) and the aver age water temperature. It is concluded that temperature had a selectiv e influence on isocitrate dehydrogenase 2, which, in contrast to isoci trate dehydrogenase 1, was identified as a mitochondrial enzyme. These findings support the hypothesis that mitochondria play a key role in temperature adaptation and the adjustment of critical temperatures.