Digestibility of krill (Euphausia superba and Thysanoessa sp.) in minke whales (Balaenoptera acutorostrata) and crabeater seals (Lobodon carcinophagus)

Abstract

Apparent digestible efficiency (% DE) was studied by use of dietary Mn as an inert marker, in minke whales (Balaenoptera acutorostrata) and crabeater seals (Lobodon carcinophagus) which had been eating krill. Median % DE in minke whales (n5) eating krill of the genus Thysanoessa sp. (energy density (ED) 23.8 kJ/g) was 93 (range 87-93). Median % DE in crabeater seals (n6) eating krill of the species Euphausia superba (ED 20.8 kJ/g) was 84 (range 79-85), which is significantly lower than the % DE of krill in minke whales (P = 0.008). Since the chemical composition in E. superba and in Thysanoessa sp. is similar, it is suggested that the complex multi-stomached system of minke whales, which contains both chitinase (EC 3.2.1.14)-producing as well as several other types of bacteria, is superior to the single-stomached system of crabeater seals with regard to krill digestion. It is worth noting, however, that the % DE of krill in the crabeater seal is still very high.