The internal reproductive system of Antarctoperlaria (Plecoptera), with special reference to the organisation of the larval ovarioles

Abstract

The gross morphology and ultrastructure of the reproductive systems of Eustheniidae and Gripopterygidae (Plecoptera: Antarctoperlaria) were investigated. Males revealed true metameric testes, a paired penis and paired male genital openings. True primary panoistic ovarioles were observed in females. As in Arctoperlaria, the ovaries of Antarctoperlaria are composed of numerous ovarioles. Terminal filaments are absent in both adult and larval ovarioles. The early larval ovarioles of Antarctoperlaria are composed of a functional germarium and a vitellarium housing previtellogenic ovarian follicles. The germaria of Gripopterygidae contained clones of germ cells interconnected via intercellular bridges. Clones were not observed in Eustheniidae. The fusion of the anterior ends of ovaries/oviducts and testes/sperm ducts is a unique character supporting Plecopteran monophyly. Metameric testicles and the paired male genital openings are regarded as plesiomorphic characters that are assumed to have been lost in other Neoptera.