Ultrastructure of spermatogenesis and sperm of the free-living soil nematode Panagrellus redivivus (Rhabditida: Panagrolaimidae)

摘要

Spermatogenesis and the structure of the mature spermatozoa were studied using TEM in a free-living nematode Panagrellus redivivus. In spermatocytes, complexes of fibrous bodies (FB) and membranous organelles (MO) develop; in spermatids, MO-FB complexes consist of typical paracrystalline FB, while free FB and MO are found in the cytoplasm of the cells. Immature spermatozoa from the proximal region of the testis are polygonal cells, the cytoplasm of which is filled with mitochondria and MO. The mature spermatozoa are polarized cells capable of forming chains. The main cell body of mature spermatozoa contains a nucleus without nuclear envelope, mitochondria and MO. Two types of MO are found in the mature spermatozoa: i) MO attached to the plasmalemma and opened to the exterior via pores; ii) MO in the cytoplasm with intact electron-dense content. The spermatozoa of P. redivivus show typical ultrastructural features of nematode sperm in general. The unusual early dissociation of FB separate P. redivivus from most rhabditids studied and resemble those described for steinernematidae