Quantitative Untersuchungen zum Dotterprotein-Haushalt der Honigbiene (Apis mellifica)

Mars is close to venus--female reproductive proteins are expressed in the fat body and reproductive tract of honey bee (Apis mellifera L.) drones

Vitellogenin (Vg) and lipophorin (Lp) are lipoproteins which play important roles in female reproductive physiology of insects. Both are actively taken up by growing oocytes and especially Vg and its receptor are considered as female-specifically expressed. The finding that the fat body of in honey bee (Apis mellifera) drones synthesizes Vg and is present in hemolymph has long been viewed as a curiosity. The recent paradigm change concerning the role played by Vg in honey bee life history, especially social division of labor, has now led us to investigate whether a physiological constellation similar to that seen in female reproduction may also be represented in the male sex. By means of Western blot analysis we could show that both Vg and Lp are present in the reproductive tract of adult drones, including the accessory (mucus) glands, but apparently are not secreted. Furthermore, we analyzed the transcript levels of the genes encoding these proteins (vg and lp), as well as their putative receptors (Amvgr and Amlpr) in fat body and accessory glands. Whereas lp, vg and Amlpr transcript levels decreased with age in both tissues, Amvgr mRNA levels increased with age in fat body. To our knowledge this is the first report that vitellogenin and its receptor are co-expressed in the reproductive system of a male insect. We interpret these findings as a cross-sexual transfer of a social physiological trait, associated with the rewiring of the juvenile hormone/vitellogenin circuitry that occurred in the female sex of honey bees.

Regulation of hypopharyngeal gland activity and oogenesis in honey bee (Apis mellifera) workers

In the honey bee, vitellogenin has several functions in addition to egg provisioning. Among others, it serves as a precursor to brood food proteins secreted by the hypopharyngeal glands of worker bees. In queenless workers with developing gonads, oogenesis and development of the hypopharyngeal glands are correlated. Here we describe two experiments that explored whether this relationship also exists in non-reproductive workers, and investigated a possible role of ecdysteroid hormones in the regulation of vitellogenin uptake. In the first experiment, the correlation between oocyte length and hypopharyngeal gland development was measured in workers before and after de-queening. In the second experiment, we induced middle-aged bees with resting glands to suddenly initiate brood care behaviour, and measured haemolymph ecdysteroid and vitellogenin titres. A strong positive relationship existed between morphometrical parameters of hypopharyngeal glands and ovaries in both queenless and queenright (functionally sterile) workers. No response of ecdysteroid titres to the addition of brood was detected in experiment 2, but high concentrations were measured in a small group of bees characterised by the possession of oocytes on the brink of yolk incorporation. We conclude that hypopharyngeal glands may belong to a previously described group of reproduction-related traits that are pleiotropically regulated in workers. A possible role for ecdysteroids in honey bee reproduction is discussed.

[Age- and caste-dependent changes in the haemolymph protein patterns ofApis mellifica]

It is only during the first days after hatching that similarities are found in the titer variations of haemolymph proteins in imagines of all castes of the honeybee. Later on caste-specific features occur.The ontogenesis of titer variations of all protein fractions is described for queens, workers, and drones. In the case of adult queens and egg-laying workers as well vitellogenin is predominant. In normal workers vitellogenic material is only present during the nurse phase. Generally the haemolymph protein pattern of worker bees shows the largest titer changes.Defined periods in the development of haemolymph protein patterns coincide with known age-dependent successions of behavioral activities. Their social regulation is discussed.