Sarcophaga bullata

Zdarek J., Nachman R. J. and Hayes T. K. (1997) Insect neuropeptides of the pyrokinin/ PB AN family accelerate pupariation in the fleshfly (Sarcophaga bullata) larvae. Anna. NY Acad. Sci. 814, 67-72. 

A number of studies with widely diverse species have established that the major site of cuticular hydrocarbon synthesis is within the cells associated with the epidermal layer or the peripheral fat body, particularly the oenocytes. In Schistocerca gregaria, Diehl (1973, 1975) separated the oenocyte-rich peripheral fat body from the central fat body tissue and observed the highest rate of hydrocarbon synthesis in the oenocyte-rich peripheral fat body. In Tenebrio molitor, Romer (1980) demonstrated that isolated oenocytes efficiently and specifically incorporated [14C]acetate into hydrocarbon. Similar studies in Periplaneta americana (Nelson, 1969), Sarcophaga bullata (Arnold and Regnier, 1975), and Musca domestica (Dillwith et al., 1981) demonstrated that hydrocarbon synthesis occurs primarily in the epidermal tissue. 

Arnold, M.T. and Regnier, F.E. (1975). Stimulation of hydrocarbon biosynthesis by ecdysterone in the flesh fly Sarcophaga bullata. J. Insect Physiol., 21,1581-1586. 

Table 2 Potencies of ecdysteroids in in vivo assays based on the induction of pup(ari)ation in ligated last-instar larvae of Dermestes vulpinus, Galleria mellonella and Sarcophaga bullata. Data are taken from Slama et al. [31] and are expressed as ED50 values (pg/g). n.d. not determined.

The biosynthesis of the juvenile hormones is not yet fully known. Their similarity to famesol, an intermediate product in the biosynthesis of steroles in mammals, leads one to assume that their formation is analogous to that of farnesol. This obvious assumption seems to be supported by publications that have appeared in the early 1970s. Barnes and Goodfellow (1971) showed that isoprenoid biosynthesis in the larva of Sarcophaga bullata proceeds with the participation of mevalonate kinase. This enzyme regulates the formation of mevalonic acid pyrophosphate, an important intermediate product in steroid biosynthesis of mammals. Isopentenyl pyrophosphate, the C, unit of isoprenoid biosynthesis, is formed from mevalonic acid pyrophosphate by decarboxylation and, with the participation of ATP, by dehydration. 

Similar conclusions were reached in a study of the growth of motoneurons in the nervous system of the fleshfly Sarcophaga bullata during metamorphosis (Nassel et al., 1986). The leg disc was removed from prepupae, thereby depriving the leg motoneurons of their target muscles. Operated flies examined after metamorphosis were missing the... 

Triterpenes and Steroids in Invertebrates Insects.—Terpenoid metabolism in insects will be considered separately from other invertebrates. Although insects do not possess the complete machinery required for biosynthesis of sterols from small molecules, it has been reported that a Sarcophaga bullata homogenate converts squalene into a compound with the chromatographic properties of squalene 2,3-oxide. However, this report warrants substantiation. The major insect juvenile hormone (133 R = Me) becomes labelled from [ C]acetate and also from l-[ H or... 

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