Food intake in Blattella germanica (L.) nymphs affects hydrocarbon synthesis and its allocation in adults between epicuticle and reproduction

The causal relationship between food intake and hydrocarbon synthesis was e xamined in vivo and in vitro. Fed Blattella germanica (L.) nymphs synthesiz ed hydrocarbons in a stage-specific manner, with high rates occurring in th e first 6 days of a 13-day last stadium, in relation to feeding. A similar pattern was exhibited in vitro by sternites and tergites hom fed nymphs. In contrast, starved nymphs synthesized hydrocarbons at normal rates for the first 2 days, but then synthesis declined and ceased by day 6. Their abdomi nal sternites and tergites displayed a similar biosynthetic pattern in vitr o, showing that starved tissues lost the capacity to synthesize hydrocarbon s, even when provided appropriate nutrients. Synthesis resumed within 2 day s of being fed on day 6, reaching a maximum rate 6 days later. Some hydroca rbon appeared on the nymphal cuticle, but almost 4-fold more hydrocarbon wa s internal in hemolymph lipophorin, fat body, and the developing imaginal c uticle. Because most hydrocarbon synthesized in nymphs provisions the adult , and synthesis is related to food intake, we examined trade-offs in alloca tions in food-limited insects. Nymphs provided with insufficient quantities of food allocated normal amounts of hydrocarbons to the nymphal epicuticle , but molted into smaller adults with significantly less internal hydrocarb ons. These cockroaches directed nearly normal amounts of hydrocarbons to th eir epicuticle, oocytes, and oothecae, at the cost of internal hydrocarbon reserves for repair and subsequent gonotrophic cycles. Hydrocarbons, thus, appear to serve an important cross-stadial resource and the object of compe tition among several nymphal and adult tissues. Arch. Insect Biochem. Physi ol. 41:214-224, 1999. (C) 1999 Wiley-Liss, Inc.