A FIELD-STUDY ON THE PHYSIOLOGY OF DIGESTION IN THE ANTARCTIC KRILL, EUPHAUSIA-SUPERBA, WITH SPECIAL REGARD TO CHITINOLYTIC ENZYMES

Endo- and exochitinase activities were determined in the stomach and m idgut gland of the Antarctic krill. Euphausia superba, along a transec t west of the Antarctic Peninsula. Activities were compared with the d igestive enzymes protease. cellulase (1,4-beta-D-glucanase) and lamina rinase (1,3-beta-D-glucanase). The chlorophyll and protein contents in the surface water of the corresponding stations were determined. Enzy me activities were characterized by high individual and spatial variat ions. Chitinolytic activity in the stomach correlated well with all di gestive enzymes investigated. In the midgut gland, a correlation with cellulase and laminarinase was evident. The amount of chlorophyll a an d phytoplankton protein in the surface water was not correlated with e nzyme activity. Specific enzyme activity was higher in the stomach tha n in the midgut gland. showing individual ratios for each enzyme. Elev ated endochitinase activity in the stomach suggests that chitinous foo d is digested to oligomers in the stomach, while the subsequent degrad ation to amino sugars occurs predominantly in the midgut gland.