Seasonality in telomerase activity in relation to cell size, DNA replication, and nutrients in the fat body of Apis mellifera

Abstract

In honeybees (Apis mellifera), the rate of aging is modulated through social interactions and according to caste differentiation and the seasonal (winter/summer) generation of workers. Winter generation workers, which hatch at the end of summer, have remarkably extended lifespans as an adaptation to the cold season when the resources required for the growth and reproduction of colonies are limited and the bees need to maintain the colony until the next spring. In contrast, the summer bees only live for several weeks. To better understand the lifespan differences between summer and winter bees, we studied the fat bodies of honeybee workers and identified several parameters that fluctuate in a season-dependent manner. In agreement with the assumption that winter workers possess greater fat body mass, our data showed gradual increases in fat body mass, the size of the fat body cells, and Vg production as the winter season proceeded, as well as contrasting gradual decreases in these parameters in the summer season. The differences in the fat bodies between winter and summer bees are accompanied by respective increases and decreases in telomerase activity and DNA replication in the fat bodies. These data show that although the fat bodies of winter bees differ significantly from those of summer bees, these differences are not a priori set when bees hatch at the end of summer or in early autumn but instead gradually evolve over the course of the season, depending on environmental factors.

Segmentation of the subcuticular fat body in Apis mellifera females with different reproductive potentials

“…The difference in the fat body mass between the reproductive and non-reproductive castes may be due to the maternal need for an increased source of energy for the mating flight. This corresponds with results obtained by Alaux et al 65 , Brütsch et al 77 and Koubová et al 78 who claim that a varied, multi-ingredient diet, particularly richer in proteins, increases the fat body mass, especially in queens.…”

Humoral and Cellular Defense Mechanisms in Rebel Workers of Apis mellifera

“…Reducing the size of oenocytes in older bees may also be associated with a reduction of JH titers. Moreover, as suggested by Koubová et al [ 59 ], this decreased fat body cell size is associated with a lower rate of DNA synthesis and lower telomerase activity. These changes result in the release of energy reserves contained in the cells [ 4 , 5 ].…”

“…In turn, oenocytes secrete ecdysteroids that regulate several functions during development and insect reproduction [ 56 , 57 ] through the production of the outer layer of egg chorion [ 58 ]. As it was mentioned, JH titer in the workers increases with age, while that of ecdysteroids decreases [ 59 ]. However, egg-laying workers have high titers of ecdysteroids.…”

“…However, egg-laying workers have high titers of ecdysteroids. These hormonal changes have an influence on oenocytes [ 5 , 59 ], whose number increased with age of bees. This may also explain why the numbers of oenocytes were always higher in rebels than in normal workers.…”

“…The length and width of these cells were higher in rebels and their values were increased until the 14th day of their lives and next, decreased. Koubová et al [ 59 ] observed that the highest diameters of oenocytes occur in December and January. It follows that the size of oenocytes depends on seasonal changes being the result of the physiological condition and phenotype of the individual.…”