Involvement of juvenile hormone in the induction of antifreeze protein production by the fat body of larvae of the beetle Dendroides canadensis

Abstract

AbstractLarvae of the Pyrochroid beetle Dendroides canadensis produce hemolymph antifreeze proteins (AFPs) as an adaptation to subzero overwintering temperatures. The AFPs are produced in early autumn in response to various environmental cues (short photoperiod, low temperature, short thermoperiod). The study presented here reinforces and extends the initial finding (Horwath and Duman, '83b) that juvenile hormone is involved in stimulating production of AFPs. Dose response curves showed seasonal variation in the sensitivity of the larvae to topical application of Juvenile Hormone (JH), with late summer larvae being more sensitive than early summer ones. The time response curve for induction of AFP activity in late summer larvae demonstrated that ∼14 days are required after JH treatment for the appearance of a significant increase in AFP activity. The timing of this response to JH induction is similar to that seen previously when larvae were acclimated to a short photoperiod.Studies with cultured fat bodies showed that the fat body is a probable site of production of the AFP, and further emphasized a role for JH in AFP induction. However, stimulation of AFP production by fat body only occurred when the fat bodies were removed from larvae that had been pretreated with JH. The presence of JH in the culture medium did not stimulate fat bodies taken from larvae that had not been pre‐treated. This suggests that an additional hormone(s), or other factor, may be required to induce fat body production of AFPs.