Influence of age and population size on ovarian development, and of trophallaxis on ovarian development and vitellogenin titres of queenless worker honey bee (Hymenoptera : Apidae)
Hr. Lin et al., Influence of age and population size on ovarian development, and of trophallaxis on ovarian development and vitellogenin titres of queenless worker honey bee (Hymenoptera : Apidae), CAN ENTOMOL, 131(5), 1999, pp. 695-706
We examined the factors that might influence ovary development in worker ho
ney bees, Apis mellifera L. Queenless workers at different ages (less than
or equal to 12 h, and 4, 8, and 21 d) were tested in cages for ovarian deve
lopment. Newly emerged, 4- and 8-d-old, and 21-d-old workers had medium-, l
arge-, and small-sized ovaries, respectively, suggesting that of the worker
ages tested only 4- and 8-d-old workers are likely to become egg layers in
a queenless colony. Also, we compared ovarian development of newly emerged
workers that were caged for 14 d and allowed to consume either pollen or r
oyal jelly to that of another group of workers similarly caged but screened
so that they could only obtain food via trophallaxis from young bees. Ovar
ies of newly emerged workers that received food from young bees were as wel
l developed as those of newly emerged workers allowed to take pollen or roy
al jelly directly. Screened workers also had lower but still elevated vitel
logenin levels compared with bees having direct access to food. These resul
ts indicate that nurse-age bees functioning as pollen-digesting units affec
t the ovarian development of other workers and to a lesser extent vitelloge
nesis via food exchange. We compared the influence of group sizes of 25, 12
5, and 600 bees per cage on ovarian development for 14 d. The two groups of
25 and 125 bees had similar mean ovary scores, and higher scores than a gr
oup of 600 bees. Our findings suggest that nurse-age bees could play an imp
ortant role in mediating worker fertility via trophallaxis, possibly by dif
ferentiating worker dominance status, and generally only young workers beco
me fertile when a queen is lost in a colony. Vitellogenin is a more sensiti
ve parameter to measure bee fertility, and might be a useful tool to furthe
r explore ovary development and egg laying in worker social insects. We rec
ommend measuring haemolymph vitellogenin titres and (or) oocyte length of w
orkers in a group of 25 bees per cage, supplied with 50% royal jelly in hon
ey as a standard method to assess honey bee worker fertility in future expe
riments.