Age, caste, and social context shape ovarian morphology and transcriptomic profiles in red harvester ants

The reproductive division of labor defines eusocial insects like ants, where queens reproduce and workers remain sterile. Yet, some workers retain rudimentary ovaries, raising questions about latent reproductive potential. We examined morphological and transcriptomic differences in Pogonomyrmex barbatus queen and worker ovaries at different maturation stages and social contexts. Queens had large, yolk-rich oocytes, while worker ovaries showed regression. Callow workers (<5 days) had more developed ovaries than mature ones (>20 days), suggesting age-related regression, even without reproduction. Queenless workers exhibited greater ovarian regression than queenright ones, indicating factors beyond queen presence may limit reproductive activation. We found ~2000 caste-specific differentially expressed genes, including those involved in metabolism, hormonal signaling, and epigenetic regulation. Queenless workers upregulated a fertility-linked gene and downregulated lipid metabolism genes. Our results show that age and social environment influence ovarian state, highlighting complex regulation of reproductive suppression and offering insight into reproductive senescence in eusocial systems.