The reproductive physiology of the fire ant, Solenopsis invicta Buren

Abstract

The male reproductive system of the fire ant, Solenopsis invicta Buren consists of the testes, vasa efferentia, vasa deferentia, seminal vesicles, accessory glands, ejaculatory duct, wedge, aedeagal bladder and external genitalia. The testes in newly eclosed males appear as 4 white lobes filled with packets of sperm. As the testes degenerate, the maturing sperm migrate into the seminal vesicles. The seminal vesicles attach to the accessory glands which are lined with secretory epithelium. The secretion of the accessory glands in immature males consists of a proteinaceous substance appearing as membrane bound vesicles in the pseudostratified columnar epithelial cells of the gland. As the males mature, the epithelial cells rupture releasing the vesicles into the lumen of the gland. The vesicles are expelled during copulation by the male into the female reproductive tract but not into the spermatheca. The posterior ends of the accessory glands unite to form the ejaculatory duct. A sclerotized wedge is present at the junction of the accessory glands and ejaculatory duct. An aedeagal bladder connects into the ejaculatory duct posterior to the wedge. The lumen of the bladder is lined with squamous epithelium enveloped by heavy musculature and contains a milky substance found in approximately equal amounts in mature, sterile and mated males. The fluid in the bladder consists of lipoproteins and fatty acid esters and has unknown functions. The ejaculatory duct continues posteriorly to form a distal aedeagus surrounded by 3 pairs of valves comprising the external genitalia. The spermathecal gland of the female reproductive system consists of two elongated lobes connected to the spermathecal duct and has unknown functions.