The importance of the spermathecal duct in bumblebees

The elongated spermathecal duct of bumblebees has been studied in hibernati ng queens, queens shortly after hibernation, mature egg-laying queens and u ninseminated queens captured during summer, and workers. Only rather small size differences are found when comparing spermathecae of queens and worker s. Clear differences between bumblebee queens and workers are found when co mparing the histochemistry of the spermathecal ducts. Adult queens, regardl ess of age and reproductive status have spermathecal ducts that contain PAS positive material, whereas workers do not. It is suggested that the polysa ccharides in the spermathecal ducts of queens are necessary as a source of energy for the rapid activation of spermatozoa passing through the duct pri or to oocyte fertilization. An ultrastructural investigation revealed the p resence of high glycogen content in the cells lining the duct of queens. As suming that sperm cells are kept in a rather inactive state in the reservoi r, the carbohydrate (glycogen) probably serves as an energy source for the sperm. The comparatively increased spermathecal duct length of bumblebees m ay increase the retention time of sperm inside the lumen. (C) 2000 Elsevier Science Ltd. All rights reserved.