Activities of proteinases in invertebrate animals--potential objects of fish nutrition. Effects of temperature, pH, and heavy metals

Differences in the degree of separate and combined effects of temperature, pH, and heavy metals (zinc, copper) on the trypsin- and chymotrypsin-like proteinase activities have been established in the whole body of some invertebrate animals - potential objects of fish nutrition: pond snail Lymnaeae stagnalis, orb snail Planorbis purpura, zebra mussel Dreissena polymorpha, oligochaetae Tubifex sp. and Lumbriculus sp. in total, chironomid larvae Chironimus sp. and Ch. riparus, as well as crustacean zooplankton. It has been shown that enzymes of the potential victim at a low temperature can compensate low activity of intestinal proteinases of fish bentho- and planktophages.