Morphology of ovaries and spermatheca of Atta sexdens (Hymenoptera: Formicidae) queens: implications for oviposition rates.

The nest of leaf-cutting ants is founded by a newly mated queen, which lays the first eggs, giving rise to workers responsible for nest construction and colony maintenance. Bioecological and physiological aspects of queens may help explain variations in the size of newly founded nests of species in the genus Atta. This study aimed to evaluate the relationship between ovary and spermatheca morphology and the oviposition rate of Atta sexdens Linnaeus (Hymenoptera: Formicidae) queens. Forty-one newly founded nests of A. sexdens were collected, and the volume of each fungus garden was measured. The queens from these nests were isolated and fed daily with the colony's symbiotic fungus to determine their daily egg production over four days. At the end of this period, the ovaries and spermathecae of the queens were dissected and analyzed under light microscopy. The oviposition rate of A. sexdens queens ranged from 0.5 to 90.5 eggs per day. Ovaries showing signs of degeneration, including yolk reabsorption in oocytes, were observed in queens with the lowest oviposition rates. Spermatheca morphology was similar among all queens. The relationship between ovarian morphology and oviposition rate in young A. sexdens queens supports the hypothesis that differences in ovarian condition contribute to variations in egg production. Such differences may ultimately influence colony growth in the field.