Influence of A. greatheadii var davyana pollen quality on ovarian development in honeybees (Apis mellifera scutellata)

In honeybee colonies there normally is a queen that lays eggs and workers that supply food and maintain the nest. However, worker bees are able to reproduce in the absence of the queen. A variety of factors, including temperature, food, pheromones and social interactions, have an influence on ovarian development. Protein-rich diets are known to promote ovarian and egg development and, since the main source of protein for honeybees is pollen, the quality and digestibility of the pollen may also have an influence. We have determined the effect of two types of pollen, sunflower and aloe, on ovarian development in queenright colonies in the field and in laboratory induced queenless groups. Extraction efficiency was determined for both pollen types. Under queenright conditions worker bees exhibited higher ovarian development when feeding on aloe pollen than on sunflower pollen. However, in queenless groups, worker bees sustained on sunflower pollen had significantly more developed ovaries compared to bees fed with aloe pollen. In addition higher mortality was observed for bees fed aloe pollen. We observed higher extraction efficiency for aloe (80%) compared to sunflower (69%) pollen in the midgut of honeybees. The higher ovarian development in workers of queenright colonies feeding on A. greatheadii var davyana may be attributed to the overall excellent nutritional content of this pollen and the high protein level (32% dry mass) in bee-collected pollen compared to the 15% in sunflower pollen. The higher extraction efficiency can be attributed to the structure and size of pollen grains, A. greatheadii var davyana pollen is bigger and smoother and better from a volume: surface point of view to digest compared to the smaller and more ornamented sunflower pollen. We explain the unexpected effect of aloe pollen on honeybee physiology in the queenless groups with the potential detrimental effects of protein in high concentrations.