Activity of Gut Alkaline Phosphatase, Proteases and Esterase in Relation to Diapause of Pharate First Instar Larvae of the Gypsy Moth, Lymantria dispar

Two distinctly different patterns of gut enzyme activity were noted in relation to diapause in pharate first instar larvae of the gypsy moth, Lymantria dispar. Trypsin, chymotrypsin, elastase, aminopeptidase and esterase activities were low at the initiation of diapause and through the period of chilling needed to terminate diapause. At the completion of a 150 day chilling period, activity of each of these enzymes quickly increased when the pharate larvae were transferred to 25°C. By contrast, activity of alkaline phosphatase (ALP) increased rapidly at the onset of diapause, remained elevated throughout diapause, increased again during postdiapause, and then dropped at the time of hatching. In addition, zymogram patterns of ALP activity differed qualitatively in relation to diapause: several bands were detectable during the pre- and postdiapause periods, but only one band, a band of high mobility, was visible during diapause. The ALP isozyme present in diapausing pharate larvae had a pH optimum of 10.6. Diapause in the gypsy moth can be averted by application of an imidazole derivative, KK-42, and pharate larvae treated with KK-42 showed elevated protease and esterase activity, low ALP activity, and expressed ALP isozymes with low mobility. Thus the overall patterns of gut enzyme activity and the ALP zymogram in KK-42 treated individuals were similar to those observed in untreated individuals at the termination of diapause. Our results suggest a unique pattern of enzyme activity in the gut that is regulated by the diapause program. Arch. Insect Biochem. Physiol. 37:197-205, 1998.