Conversion of ergosterol to 22-de-hydrocholesterol in Blattella germanica.

The literature suggests that several species of insects can convert Czs and Czs sterols to cholestane derivatives. According to Bergmann (l), cholesterol is the major sterol constituent (85%) and the plant sterol sitosterol a minor component of chrysalis oil obtained from the silkworm Bombyx mori, although this insect feeds exclusively on mulberry leaves. More recently, Bergmann and Levinson (2) have investigated the sterols of dried preparations of two other phytophagous insects, Colias hyale, Godt, and Orgyra antiqua, L. The ability of a Dermestid to grow on these preparations without cholesterol supplements was used as an assay. The studies of these investigators also included dried preparations of the larvae of Musca vicina fed on a wheat bran diet. It was concluded that in all three cases the insects were able to convert dietary “phytosterols” to “zoosterols” which the Dermestid can utilize. Furthermore, Beck and Kapadia (3) have examined by paper chromatography the sterol content of larvae of the flour beetle Tribolium con&sum maintained on a completely synthetic diet. In this brief report it is stated that the principal tissue sterols were invariably 7-dehydrocholesterol and cholesterol whether the dietary sterol was cholesterol, 7-dehydrocholesterol, cholestanol, sitosterol, or ergosterol. We have now undertaken an investigation of the conversion of Czs sterols to cholestane derivatives in nymphs of the German cockroach, Blattella germanica. This insect, in contrast to the Dermestid beetle, grows and develops normally on synthetic diets containing ergosterol as the sole sterol source. With the aid of uniformly labeled and C-28 labeled ergosterol, it is shown that the roach nymphs form a sterol which no longer contains the methyl substituent at C-24. The present paper furthermore deals with the isolation and identification of this demethylation product.