COMPARISONS BETWEEN THE 12S RIBOSOMAL-RNA, 16S RIBOSOMAL-RNA, NADH1 AND COI GENES OF SPERM AND FIN WHALE MITOCHONDRIAL-DNA

Two regions of the mitochondrial DNA molecule of the sperm whale (Physeter macrocephalus) were cloned and sequenced. The regions comprised the 12S and 16S rRNA genes and the peptide coding genes NADH1 and COI. The four genes were compared with the corresponding genes of the fin whale (Balaenoptera physalus) and the cow. Two portions of delphinid mitochondrial 16S rRNA from the literature were also included in the comparison. Conservative differences between the sperm and fin whale were approximately 50% of the difference between either whale species and the cow. Provided the evolution of the four genes is linearly related to time, the odontocete lineage represented by the sperm whale and the mysticete lineage represented by the fin whale separated 25-30 million years ago. Analyses of the two partial 16S rRNA sequences did not group the two odontocetes together.