Site of synthesis, tissue distribution, and lipophorin transport of hydrocarbons in Blattella germanica (L.) nymphs

The site of hydrocarbon (HC) synthesis and the amount of HC in various tiss ues were investigated in relation to developmental stage in the last larval stadium of the German cockroach, Blattella germanica. Abdominal integument linearly incorporated [1-C-14]propionate into HC for at least 6 h in vitro , whereas other body parts synthesized little or no HC. The third through s ixth abdominal sternites and tergites were the principal sites of synthesis . High rates of HC synthesis resulted in a fivefold increase in internal HC during the last stadium. We examined the distribution of HC in the hemolym ph, fat body, and the developing imaginal cuticle. Hemolymph HC titer was r elatively constant at approximate to 8 mu g/mu l. However, as hemolymph vol ume increased from 5 to 11 mu l in the first 4 days of the last stadium, HC content increased and then remained stable the remainder of the stadium. L ipophorin, immunoprecipitated with adult lipophorin polyclonal antibodies, was the only HC carrier protein in nymphal hemolymph and its HC profile was identical to that of hemolymph and similar to that of the epicuticle. The concentration and total amount of hemolymph lipophorin increased until 3 da ys before adult eclosion and declined immediately after ecdysis. The HC con tent of non-biosynthetic integument (legs, pronotum) doubled during formati on of the imaginal cuticle, as did the HC content of sternites, which synth esize HC. HC content of fat body, however, increased threefold during the s ame period, suggesting that the fat body serves as a storage site for HC du ring cuticle formation. We conclude that in the last stadium HC is synthesi zed by abdominal oenocytes, loaded onto hemolymph lipophorin, and transport ed to fat body and both nymphal and imaginal cuticle. Hydrocarbons associat e with the imaginal integument several days before eclosion. (C) 1999 Elsev ier Science Ltd. All rights reserved.