Size and growth of heart, liver, and kidneys in North Atlantic fin (Balaenoptera physalus), sei (B. borealis), and sperm (Physeter macrocephalus) whales

Abstract

Size and growth of heart, liver, and kidneys in fin (Balaenoptera physalus), sei (B. borealis), and sperm (Physeter macrocephalus) whales taken commercially off Iceland during the 1980 season are compared and examined relative to organ weights for terrestrial mammals. In agreement with the work of previous investigators, the sperm whale is shown to have a relatively smaller heart. However, contrary to previous analysis, fin and sei whales are shown to have relative heart sizes not radically different from those of terrestrial mammals. It is suggested that the differences in relative heart size between the baleen and toothed whales are a reflection of the greater swimming speeds that the baleen whales are capable of attaining. This analysis confirms that marine cetaceans have relatively much larger livers than terrestrial mammals and that they also appear to have relatively larger kidneys. The results presented here, however, show fin, sei, and sperm whales to have relative kidney sizes less than half as great as those given in previous analyses. Growth gradients in the three organs show a distinct pattern of divergence between sperm (Odontocete) and fin and sei (Mysticete) whales.