Neutral sterols in honey bee (Apis mellifera) feces

Abstract

Nutrition is important in honey bee (Apis mellifera L.) colony decline. While the honey bee is incapable of converting dietary plant sterols to cholesterol, the sterol 24-methylenecholesterol has been previously shown to be selectively transferred from worker honey bees to developing brood in both laboratory and field studies. The importance of 24-methylenecholesterol to honey bee development and nutrition is unknown. This selective transfer suggests either (i) honey bees concentrate 24-methylenecholesterol in their tissues by selectively excreting other sterols in their feces (hypothesis 1), or (ii) some other metabolic/physiological mechanism exists to segregate/sequester 24-methylencholesterol for transfer to brood (hypothesis 2). The objective of this study was to determine if any C28 and C29 sterols other than 24-methylenecholesterol were selectively excreted in the feces by the honey bee (hypothesis 1), thereby concentrating the relative percentages of 24-methylenecholesterol in worker bee tissue, and thereby partially explaining the mechanism of selective sterol transfer in honey bees. We conducted the study by confining worker honey bees in a small cage with glass sides to facilitate the collection of honey bee feces. After four days, the neutral sterols were identified and the percentages of these sterols were determined from the pollen the honey bees presumably consumed prior to confinement, from the tissues of the confined worker bees, and from their feces. There was no apparent excessive excretion of other C28 and C29 phytosterols such as campesterol, sitosterol and isofucosterol and stigmasterol in honey bee feces, suggesting that hypothesis 2 (above) needs investigation.