Age at sexual maturity of male and female banana weevils, Cosmopolites sordidus Germar (Coleoptera: Curculionidae)

Abstract

This study was to determine the age at sexual maturity and the relationships between age and internal reproductive organs of Cosmopolites sordidus. Male banana weevils become sexually mature 18 days after emergence (DAE), that is after 2 weeks of adult eclosion, in spite of the fact that spermatogenesis is completed at emergence. A positive correlation exists between age and male internal organs, for example for mean testis diameter (r = .849, p ≤ .001), mean seminal vesicle diameter (r = .679, p ≤ .001), mean accessory gland length (r = .561, p ≤ .01) and mean accessory gland diameter (r = .498, p ≤ .05), respectively. Significant differences were recorded between sexually mature and immature weevils with respect to mean testis diameter (T = 4.471, p ≤ .001) and mean seminal vesicle diameter (T = 3.939, p ≤ .001), but not with mean accessory gland length and mean accessory gland diameter (T = 1.899 and 1.661). Male internal organs were visibly underdeveloped at emergence but became significantly enlarged and developed on attainment of sexual maturity. Female C. sordidus, on the other hand, are sexually mature at 5 DAE. There was also a strong, positive correlation between age of females and mean ovariole length (r = .656, p ≤ .001), and significant differences existed between mean ovariole lengths of sexually mature and immature females (T = 4.306, p ≤ .001). Increasing age of females witnessed progressive increases in ovariole lengths and developmental changes within female ovarioles and calyces. The findings made here may be helpful in Musa germplasm screening works, as weevils bred on susceptible cultivars may reveal similar results, while those bred on resistant ones may experience possible delays in their reproductive developments.