Flight induced lipid mobilization and enhanced reproduction in Melanoplus sanguinipes

K.J. Min & M. A. Rankin

Integrative Biology Section, School of Biological Science, Univ. of Texas, Austin, TX 78712, USA

One way of possible stimulation of the endocrine system by flight in grasshopper, Melanoplus sanguinipes, was examined. It is known that long flight accelerates oogenesis in this species. One possible mechanism of accelerated reproduction is via lipid delivery to the ovary during and (or) after flight. Lipid is mobilized by adipokinetic hormone into hemolymph during flight and could be available to ovary. The lipid content of eggs was examined after flight. The lipid content of eggs of long-fliers that flew to voluntary cessation (LF-E), was lower than that of non-fliers (NF) or hoppers flown to one hour (LF-1). The carbohydrate content of eggs was also lower in long fliers than non-fliers and there was no difference in protein content in eggs. This indicates that accelerated oogenesis is not by action of lipid delivery. However, when the number of eggs in each individual first egg pod was examined, that of long-fliers flown to voluntary cessation was higher than that of non-fliers and long-fliers flown to one hour. Because it is known that the grasshopper uses only a small portion of its lipid reserve during flight to voluntary cessation, reduced lipid content in eggs of long duration flier is probably not due to depleted lipid reserve. Instead it seems that more eggs are produced having less nutrient per egg, possibly due to accelerated oogenesis or oviposition after long flight. Thus it seems that accelerated reproduction is unrelated to lipid mobilization, but may be due to other endocrine change during flight. This possibility is under investigation.

Index terms : grasshopper, migration, egg, lipid

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