Adipokinetic Hormones in Fifth instar Romalea guttata (Orthoptera: Acrididae): Activation of Glycogen Phosphorylase Does Not Produce Hypertrehalosemia

Abstract

Romalea guttata Houttuyn (= R. microptera Beavois) is flightless, lethargic, aposematic, and chemically defended. R. guttata stores large quantities of two adipokinetic hormone (AKH) family peptides in its corpora cardiaca. In adults, these peptides (Rom-CC-I and Grb-AKH) activate fat body glycogen phosphorylase but are not hypertrehalosemic. Because juvenile R. guttata contain sufficient peptide to be bioactive, we sought to determine whether these peptides are hypertrehalosemic, phosphorylase activating, or hyperlipemic in juveniles. Late fifth (= last) instar and adult R. guttata activated phosphorylase in response to Rom-CC-I injections. These same individuals showed no hypertrehalosemia in response to Rom-CC-I. We hypothesize that the glycogenolysis pathway is not started by activation of glycogen phosphorylase in response to Rom-CC-I. From fourth instar through third week adult, R. guttata showed a slight, statistically insignificant hypolipemia, but clearly no hyperlipemia. R. guttata differs from Locusta migratoria in that it appears to show neither hypertrehalosemia nor hyperlipemia at any developmental stage.