Nutritional indices and digestive enzyme activities of gypsy moth larvae switched between turkey and hungarian oak

Abstract

Larvae of a generalist species, the gypsy moth (Lymantria dispar), frequently encounter diet heterogeneity due to passive wind-born dispersal of 1st instar as well as host plant switching of advanced instars in mixed stands and during outbreak. Such spatial and temporal variation in nutritional environment favors their exquisite behavioral and physiological plasticity. We studied the effects of switching between Turkey (Quercus cerris) and Hungarian oak (Q. frainetto) on growth, nutritional indices and activities of protease and amylase in gypsy moth larvae. In Serbia, these oak species are often found in mixed stands where outbreaks start. Hungarian oak is less suitable host plant due to lower water and protein content. Switching from turkey to hungarian oak led to prolonged duration of 4th instar, decreased relative growth rate, relative consumption rate and efficiency of conversion of ingested food as well as increased protease and amylase activity. Values of examined traits in gypsy moth larvae switched from hungarian to turkey oak did not differ from values obtained in larvae continuously reared on turkey oak. Studying physiological plasticity of the gypsy moth in response to variation in suitable hosts are important for understanding population dynamics of this invasive species.