Post-Embryonic Gonad Development in the Capital-Breeding Seed Beetle Zabrotes subfasciatus (Bruchinae): A Morphological View

Abstract

Simple Summary Seed beetles are important pests of stored legumes, but little is known about how their reproductive organs develop before adulthood. This study examined the formation of ovaries and testes in Zabrotes subfasciatus, a bean weevil whose adults depend mainly on reserves accumulated while feeding inside seeds as larvae. Using stereomicroscopy, histology, and scanning electron microscopy, we found that gonad development starts during larval life but that the main changes leading to reproductive readiness occur during late metamorphosis, especially between the pupal and pharate-adult stages. In females, this period includes the organization of the ovaries, the appearance of developing oocytes, follicular cells, trophic cords, and the first signs of yolk deposition, showing that egg maturation begins before adult emergence. In males, the testes also mature early, with advanced sperm development already evident before emergence. These results help explain why newly emerged adults of this pest can become reproductively active quickly and provide useful information for future studies on reproductive biology and pest-management strategies.