Activities of chitinase and protease and concentration of fluoride in the digestive tract of Antarctic fishes feeding on krill (Euphausia superba Dana).

Studies on the digestion of krill by Notothenia rossii marmorata, Notothenia neglecta, Champsocephalus gunnari and Chaenocephalus aceratus showed that these Antarctic fish species are well equipped to feed on krill, as indicated by their high levels of chitinase and protease activity. Very high chitinolytic activities were determined in the stomach of the fish species. However, activities that were measured in intestine samples can be substantial, as well. Very strong protease activities were determined in samples of the stomach tissue and the intestinal contents. When krill were present in the guts, the concentrations of fluoride in the stomach and intestinal contents of N. rossii marmorata and Ch. gunnari were extremely high, while the tissues were practically devoid of fluoride.