Neutral Sterols of Cephalic Glands of Stingless Bees and Their Correlation with Sterols from Pollen

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 sterols de novo and, 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 in Melipona marginata and Melipona scutellaris colonies, 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 in M. scutellaris glands. Surprisingly, cholesterol was found in some glands with relative ratios greater than those found in pollen

Cuticular Hydrocarbons Discriminate Distinct Colonies of Melipona marginata (Hymenoptera, Apinae, Meliponini)

The aim of the present study was to characterize the variation of the chemical profiles among workers in different colonies of the stingless bee Melipona marginata. We used gas chromatography and mass spectrometry (CG-MS) and multivariate analysis of the bees’ chemical from three colonies of two localities in southeast Brazil. The results showed that cuticular hydrocarbon profiles clearly separated distinct colonies. We show here the importance of using the chemical analyses for characterization of colony membership, in addition of the traditional techniques of diversity analyses

Cuticular Hydrocarbons Discriminate Distinct Colonies of Melipona marginata (Hymenoptera, Apinae, Meliponini)

The aim of the present study was to characterize the variation of the chemical profiles among workers in different colonies of the stingless bee Melipona marginata. We used gas chromatography and mass spectrometry (CG-MS) and multivariate analysis of the bees' chemical from three colonies of two localities in southeast Brazil. The results showed that cuticular hydrocarbon profiles clearly separated distinct colonies. We show here the importance of using the chemical analyses for characterization of colony membership, in addition of the traditional techniques of diversity analyses.CNPq [134833/2006-6]CNPqCAPESCapesFAPESPFapesp [Proc. 04/09479-8

First record of chemical signals from the queen during the oviposition process in stingless bees

In stingless bees, the cell provisioning and oviposition process consists of several integrated behavioral sequences and several stereotyped queen-worker interactions. This study aims to demonstrate that chemical signals originating from the queen may contribute as cues for the sequence of the oviposition process in Melipona marginata. For this, we analyzed the cell before and after queen laying, and compared them with the cuticular hydrocarbons of the queen's abdomen, using a gas-chromatography and mass spectrometry system

Characterization of cuticular hydrocarbons of diploid and haploid males, workers and queens of the stingless bee Melipona quadrifasciata

Males, queens and workers of stingless bees show differences in external morphology, behaviour and roles within a colony. In addition, each individual has a cuticular chemical signature responsible for mutual communication that is essential for maintaining the integrity of the colony. In this paper we characterize the cuticular hydrocarbon composition of newly emerged diploid and haploid males, workers and virgin queens of Melipona quadrifasciata by gas chromatography-mass spectrometry (GC/MS) analysis. This is the first time that the cuticular profile of diploid males in a species of stingless bee has been characterized. We found differences in the cuticular hydrocarbon composition among males, workers and virgin queens, recording both qualitative and quantitative differences among individuals of different phenotypes. However, no compound was found exclusively in diploid males. The cuticular chemical profiles of haploid and diploid males were very similar to those of workers. Moreover, the cuticular lipids of males and workers were significantly different from those of queens. Tricosane, pentacosene-2 and 7-methyl-heptacosane were the compounds responsible for this significant separation. This result correlates with the behavioural and morphological differences among these phenotypes.Fundacao de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG)Fundacao de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG)CNPqCNP

Exploring integument transcriptomes, cuticle ultrastructure, and cuticular hydrocarbons profiles in eusocial and solitary bee species displaying heterochronic adult cuticle maturation.

Differences in the timing of exoskeleton melanization and sclerotization are evident when comparing eusocial and solitary bees. This cuticular maturation heterochrony may be associated with life style, considering that eusocial bees remain protected inside the nest for many days after emergence, while the solitary bees immediately start outside activities. To address this issue, we characterized gene expression using large-scale RNA sequencing (RNA-seq), and quantified cuticular hydrocarbon (CHC) through gas chromatography-mass spectrometry in comparative studies of the integument (cuticle plus its underlying epidermis) of two eusocial and a solitary bee species. In addition, we used transmission electron microscopy (TEM) for studying the developing cuticle of these and other three bee species also differing in life style. We found 13,200, 55,209 and 30,161 transcript types in the integument of the eusocial Apis mellifera and Frieseomelitta varia, and the solitary Centris analis, respectively. In general, structural cuticle proteins and chitin-related genes were upregulated in pharate-adults and newly-emerged bees whereas transcripts for odorant binding proteins, cytochrome P450 and antioxidant proteins were overrepresented in foragers. Consistent with our hypothesis, a distance correlation analysis based on the differentially expressed genes suggested delayed cuticle maturation in A. mellifera in comparison to the solitary bee. However, this was not confirmed in the comparison with F. varia. The expression profiles of 27 of 119 genes displaying functional attributes related to cuticle formation/differentiation were positively correlated between A. mellifera and F. varia, and negatively or non-correlated with C. analis, suggesting roles in cuticular maturation heterochrony. However, we also found transcript profiles positively correlated between each one of the eusocial species and C. analis. Gene co-expression networks greatly differed between the bee species, but we identified common gene interactions exclusively between the eusocial species. Except for F. varia, the TEM analysis is consistent with cuticle development timing adapted to the social or solitary life style. In support to our hypothesis, the absolute quantities of n-alkanes and unsaturated CHCs were significantly higher in foragers than in the earlier developmental phases of the eusocial bees, but did not discriminate newly-emerged from foragers in C. analis. By highlighting differences in integument gene expression, cuticle ultrastructure, and CHC profiles between eusocial and solitary bees, our data provided insights into the process of heterochronic cuticle maturation associated to the way of life