Abstract
Sterols are essential molecules in the membrane lipid composition and precursors of important sterol hormones that regulate many developmental processes. Insects are unable to synthesize sterolsde novoand, thus, all phytophagous insects depend on an exogenous source of sterols for growth, development, and reproduction. The sterol requirements of social bees are not fully known due to the fact that there is no well-defined diet available throughout the year with regard to floral resources. Our study aimed to characterize the sterols present in pollen stored inMelipona marginataandMelipona scutellariscolonies, as well as evaluating their presence in the mandibular, hypopharyngeal, and cephalic salivary gland secretions. We analyzed the chemical composition of pollen stored in the colonies and the composition of the cephalic glands of workers in three adult functional phases (newly emerged, nurses, and foragers) by gas chromatography and mass spectrometry. The results showed that the pollen analyzed contained campesterol, stigmasterol, sitosterol, isofucosterol, lanosterol, and small amounts of cholesterol. The glands showed the same compounds found in the pollen analyzed, except lanosterol that was not found inM. scutellarisglands. Surprisingly, cholesterol was found in some glands with relative ratios greater than those found in pollen.
Highlights
Sterols are essential molecules in cell membrane, they are precursors of sterol hormones and other important regulators of developmental processes
Results of sterol analyses of pollen, hypopharyngeal glands (HYP), labial glands (LAB), and mandibular glands (MAN) of Melipona marginata and Melipona scutellaris are summarized in Tables 1 and 2
The only exception was the absence of lanosterol in the glands of M. scutellaris bees, even though it is present in pollen collected in pots
Summary
Sterols are essential molecules in cell membrane, they are precursors of sterol hormones and other important regulators of developmental processes. Insects are unable to synthesize them and have to purchase sterols from their diet [1]. The dietary needs for sterols in insects were firstly reported by Hobson [2] in the blowfly Lucilia sericata. In 1959, Clark and Bloch [3] showed the inability of insects to synthesize sterols de novo, so that they need to purchase these compounds for auxotrophy (from the Greek “to increase” and “nutrition”). Auxotrophic individuals are unable to synthesize organic compounds necessary for its growth. These authors showed the importance of sterols as structural (cholestanol) and metabolic (cholesterol) components in insects. Further studies showed that ecdysteroids derivatives from cholesterol participate in the control of insect growth and maturation [4]
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