-Investigations on physiological and molecular mechanisms underlying developmental and reproductive differentiation in social bees center on the question of how different patterns of larval nutrition can affect hormonal dynamics and how these drive differential gene expression. Differential expression analyses and the generation of AFLP markers now enable us to re-examine the question of genetic caste determination in the genus Melipona. The comparison of vitellogenin expression in three species of stingless bees suggests divergence in regulatory mechanisms that directly relate to the mode of worker reproduction. As in honey bees, this indicates alternative functions for vitellogenin in the life cycle of adult workers. The diversity in life histories and their associated specific physiologies make the stingless bees a rich resource for information on evolutionary trajectories that have generated phenotypic plasticity in social Hymenoptera. stingless bee / caste development / juvenile hormone / vitellogenin / worker reproduction / Apidae / Meliponini

Insect hexamerins have long been known as storage proteins that are massively synthesized by the larval fat body and secreted into hemolymph. Following the larval-to-pupal molt, hexamerins are sequestered by the fat body via receptor-mediated endocytosis, broken up, and used as amino acid resources for metamorphosis. In the honey bee, the transcript and protein subunit of a hexamerin, HEX 70a, were also detected in ovaries and testes. Aiming to identify the subcellular localization of HEX 70a in the female and male gonads, we used a specific antibody in whole mount preparations of ovaries and testes for analysis by confocal laser-scanning microscopy. Intranuclear HEX 70a foci were evidenced in germ and somatic cells of ovarioles and testioles of pharate-adult workers and drones, suggesting a regulatory or structural role. Following injection of the thymidine analog EdU we observed co-labeling with HEX 70a in ovariole cell nuclei, inferring possible HEX 70a involvement in cell proliferation. Further support to this hypothesis came from an injection of anti-HEX 70a into newly ecdysed queen pupae where it had a negative effect on ovariole thickening. HEX 70a foci were also detected in ovarioles of egg laying queens, particularly in the nuclei of the highly polyploid nurse cells and in proliferating follicle cells. Additional roles for this storage protein are indicated by the detection of nuclear HEX 70a foci in post-meiotic spermatids and spermatozoa. Taken together, these results imply undescribed roles for HEX 70a in the developing gonads of the honey bee and raise the possibility that other hexamerins may also have tissue specific functions.

The strong dimorphism in ovary phenotype seen between honey bee queens and workers represents the anatomical fixation of reproductive division of labor. We review the developmental processes by which the divergent ovary phenotypes become established, mainly focusing on the massive programmed cell death (PCD) that destroys most of the ovariole primordia in the worker ovary during larval development. Ovary-specific transcriptome analyses revealed a set of differentially expressed genes associated with PCD, including two long noncoding RNAs. PCD also plays a major role regulating ovarian activity in adult honey bee workers, and a major effect candidate gene mediating this process is Anarchy , previously identified through classical genetics in a rebel worker strain. Finally, we ask how the strong ovary phenotype dimorphism in the genus Apis may have evolved, and we discuss this by contrasting honey bees with the equally eusocial stingless bees. Through a comparison of their mating systems (polyandry versus monandry), as well as comparative data on female and male gonad structure across several families of bees, we propose the hypothesis that the exceptional gonad structure in Apis queens and drones evolved via shared developmental pathways. Furthermore, we suggest that selection on massive sperm production in Apis drones may have been a driving force leading to this exaggerated gonad morphology. honeybee / gonad development / cell death / differential gene expression / meliponids Where does the spirit of the hive reside? At least to some extent it is in the ovaries of a crowd of bees working in a dark hive (Robert E.

Like Apis mellifera queens and different from all other bees, drones also have an exaggerated gonad phenotype, with over 150 serial units in each gonad. Yet, compared with the ovaries of the female castes, little is known about the development of the honey bee testis. Here we present a histological atlas on postembryonic testis development and spermatogenesis. Already in the first instar larvae, the testioles composing each testis can be distinguished. The testioles then grow along their apical-basal axis by mitotic divisions of the spermatogonia, which eventually form germ cell clusters. Meiosis starts when brood cells are capped, and it ends with the appearance of spermatids in red-eyed pupae. Subsequently, spermiogenesis takes place, and all spermatozoa are formed before adult emergence. We also present the first data on juvenile hormone levels in drone larvae. With this, we provide a database for future research on gonad development in honey bee drones.