Ultrastructure of Spermiogenesis and Sperm of an Undescribed Species of Luridae (Platyhelminthes, Rhabdocoela)

Abstract

Testis follicles of an undescribed species of Luridae (Dalyellioida) contain nurse cells with cytoplasmic processes branching between the spermatids. Spermatids elongate to form aflagellate and non-axonemal sperm containing an elongate nucleus, mitochondria and dense bodies. Up to 15 peripheral microtubules are longitudinally directed in mature sperm, but are arranged in a screw-like fashion in elongating spermatids. Non-axonemal sperm have evolved independently in species of several platyhelminth taxa: Monogenea, Prolecithophora, Dalyellioida, and Catenulida.