Structural Changes in the Male Reproductive Tract of the Stingless Bee Scaptotrigona xanthotricha Moure 1950 (Meliponini, Apidae) During Sexual Maturation

Abstract

Stingless bees are social insects widely distributed in the Neotropical region but the loss of habitats and the increased use of pesticides in agriculture have threatened the bee populations. Thus, the knowledge of the biology of these insects, including reproductive biology is important for their conservation and management. This study describes the morphological changes in the male reproductive tract during the sexual maturation in the stingless bee Scaptotrigona xanthotricha (Moure 1950). The reproductive tract was investigated under light microscopy from young pupae to 22 days old adults. The male reproductive organs in S. xanthotricha are a pair of testes, each with four follicles, pair of vasa deferentia with enlarged region forming the seminal vesicle that open in an ejaculatory duct. In the male reproductive system of these bees there is no structure that can be recognized as accessory glands as seen in insects in general. From brown-eyed pupae to newly-emerged adults, the epithelia of the seminal vesicles and post-vesicular vasa deferentia have prismatic cells that release secretion to the organs lumen. In 5-days old adults the testes undergo degeneration, the seminal vesicles filled with secretion and spermatozoa, and the epithelium has cubic cells rich in inclusions in the basal region suggesting that this is the age in which males reach the sexual maturation. Structural modifications in the reproductive tract during sexual maturation are discussed concerning the reproductive biology of Meliponini.