Ant queens store viable sperm in their spermatheca throughout their lifetime, while in most species workers cannot. We compared the histological organization of the sperm reservoir of 25 poneromorph ant species with varying degrees of queen-worker dimorphism. All species had a similar spermatheca layout consisting of a reservoir connected to the oviduct with a sperm duct, a paired spermatheca gland opening into this duct, as well as similar ultrastructural organization of tissues. We found no consistent differences in associated structures such as the spermatheca gland or sperm ducts, nor in musculature between queens and sterile workers. The sperm reservoir, however, shows a crucial morphological difference related to functionality. Queens typically have a columnar epithelium in the hilar region near the opening of the sperm duct (Gobin et al. 2006). These cells have abundant mitochondria, apical microvilli and basal invaginations, but lack Golgi apparatus and endoplasmic reticulum. This ultrastructural organization is similar to epithelia described in the queens of the ant Crematogaster and the honey bee (Dallai 1975; Wheeler and Krutzsch 1994), and is typical of transport epithelia. The columnar region likely has an important osmoregulatory function. In contrast, the reservoir epithelium of permanently virgin workers is cuboidal and lacks these transport characteristics throughout. This result shows the importance of a columnar epithelium in the hilar region for sperm storage, which was confirmed in gamergate species where workers are able to mate and store sperm.
 
References
Dallai R (1975) J Insect Physiol 21:89-109
Gobin B et al. (2006) Cell and Tissue Research in press
Wheeler D and Krutzsch P (1994) Zoomorphology 114:203-212