Comparative morphology of reproductive and trophic eggs in melipona bees (Apidae, Meliponini)

ABSTRACT

The process of cell provisioning and oviposition (POP) in stingless bees involves highly complex interactionsbetween the queen and workers. During this process, workers can usually lay two types of eggs, referred toas reproductive and trophic. Reproductive worker-laid eggs are unfertilized but develop into males whereastrophic worker-laid eggs are eaten by the queen immediately after oviposition. Although the egg-layingactivity of reproductive workers varies considerably among species, the laying of trophic eggs appears to bethe rule in Melipona bees. In this work, we examined whether the morphology of eggs laid by workers andqueens of M. scutellaris, M. compressipes fasciculata and M. asilvai was similar to that of other Meliponaspecies. Egg morphology was examined by scanning electron microscopy whereas egg size was measured bylight microscopy. In all of the species studied, the chorion of queen and worker reproductive eggs showed acharacteristic reticulate pattern. The surface of trophic eggs was not reticulate and had an irregular appearancefollowing fixation. Trophic eggs were also invariably smaller than queen-laid eggs and were sometimessmaller than worker-laid reproductive eggs. These findings indicate that trophic eggs can be smaller than theeggs of functional workers, which suggests that the development of this type of egg is probably associatedwith different physiological adaptations.