Intestinal protein dynamics in the stonefly, Pteronarcys californica

Characteristics of the intestinal proteins of a detritus-eating aquatic insect, Pteronarcys californica were assessed to determine their possible role as a nutrient source during metamorphosis. Total soluble intestinal protein was significantly correlated to larval weitht, averaging 3.9% of dry weight for both males and females. Proteinase activity in the gut was separated into several bands by electrophoresis. Electrophoresis patterns of total intestinal proteins of P. californica larvae of differing instar, sex, and diet were remarkably similar. Larvae incubated with tritium-labelled amino acids produced labelled intestinal proteins. When early instar larvae were removed from label, there was no significant loss of tritium from the intestine after 2 months. Penultimate instars labelled in the same manner however, showed depuration of tritium from the gut according to first order kinetics. This loss was correlated to the 6–8 wk non-feeding stage of metamorphosis, just prior to adult emergence. These results indicate that proteins are accumulated in the intestinal tract of immature P. californica, then are reabsorbed from the gut during metamorphosis.