Lipid, carbohydrate and nitrogen content of long- and short-winged Gryllus firmus: Implications for the physiological cost of flight capability

Abstract

Concentrations of total lipid, triglyceride, soluble carbohydrate, total nitrogen and water were measured in the long-winged (LW) and short-winged (SW) morphs of the cricket, Gryllus firmus. In addition, the weights and composition of wings and oviposited eggs were compared between morphs. This was done to obtain information on the energetic cost of flight capability in the LW morph. Whole-cricket content (% dry mass) of triglyceride was significantly higher in LW vs SW individuals of both sexes. Since triglyceride is a likely flight fuel in G. firmus, the biosynthesis of elevated levels of this high energy substance in the LW morph may represent an important energetic cost of flight capability. The existence of such a cost is consistent with the elevated respiratory metabolism previously observed in LW vs SW G. firmus. A highly significant negative correlation was observed between triglycerides and non-triglycerides in LW but not SW crickets. This suggests that lipid biosynthesis may be operating under some constraint in the LW morph. Increased triglyceride biosynthesis may require a concomitant decreased biosynthesis of non-triglycerides. In contrast to the elevated triglyceride level in the LW morph, carbohydrate concentration was higher in the SW morph during early adulthood. Carbohydrate content also decreased with age in the SW but not in the LW adults. No differences were observed between morphs in (1) the total nitrogen or water contents of whole crickets, (2) the nitrogen content of wings or (3) the wet weight, dry weight, lipid content, or total nitrogen content of oviposited eggs.