Sterol Utilization in the Hide Beetle, Dermestes vulpinus

A dietary supply of sterol is an indispensable growth requirement for all species of insects that have been studied (l-3).This requirement has been found to be satisfied in all cases by cholesterol, and in most by either cholesterol or a phytosterol, although in a given insect species growth is not always as rapid with some types of sterols as with others (4-6).Earlier reports from this laboratory (7) have described the detailed investigation of the dietary sterol requirement of the carnivorous beetle, Dermestes vulpinus.By virtue of its feeding habits, this insect normally utilizes cholesterol as its major dietary sterol; of a variety of different sterols that were tested in this investigation, only two, desmosterol and 24.methylenecholesterol, were found to be capable of completely replacing cholesterol in the diet of this insect.The further observation was made, however, that several sterols of different structural types, although unable to replace in its entirety the normal cholesterol requirement of D. vulpinus, were able to spare, i.e. replace, the major part of it.An assay method was devised that permitted the classification of sterols according to their efficiency as cholesterol sparers for this insect, and some tentative conclusions were drawn concerning the influence of various features of molecular structure upon their cholesterol-sparing efficiency.The hypothesis was advanced that the sterols utilized by the insect as partial replacers of,its normal cholesterol requirement were incorporated into its tissues unchanged and performed an essential role in the maintenance of the structural integrity of the cells.These studies seemed likely to yield significant information concerning the physical characteristics of the spaces in which such sterol "building blocks" are normally accommodated.They have been continued with this object in mind, therefore, and the present communication represents a summary of the results obtained with more than 30 different sterols. EXPERIMENTAL PROCEDURESterols-The sources of the various sterols used in this study are shown in Table I.Their purity was tested in all cases by gas-liquid chromatography as described by Clayton (8).Where impurities were detected, attention is drawn to this, but in no case was the percentage of impurities such as to cast doubt on the validity of the results of the biological tests.Insects-The insects, Dermestes vulpinus, were descendants of the same stock colony that had been used for the earlier studies in this laboratory, and