Spermatogenesis and spermatozoon ultrastructure in the jawed bloodfeeding land leechHaemadipsa japonica (Hirudinida: Hirudiniformes) from Japan

Abstract

Ben Ahmed R., Nakano T., Piątek J., Krzyzczyk R., Świątek P. 2023. Spermatogenesis and spermato- zoon ultrastructure in the jawed bloodfeeding land leech Haemadipsa japonica (Hirudinida: Hirudiniformes) from Japan Folia Biologica (Kraków) 71 : 207-220. The aim of this study is to describe spermatogenesis and spermiogenesis in the jawed sanguivorous land leech Haemadipsa japonica Whitman, 1886, for the first time, using both light and electron microscopy. Spermatogenesis occurs within testisacs, where numerous cysts (clusters) of interconnected spermatogonia, spermatocytes and spermatids freely float in the fluid. In a given cyst, the interconnected germ cells develop in synchrony, i.e.spermatogonial cysts, and cysts with spermatocytes or spermatids can be observed. During spermiogenesis, the spermatids transform into typical hirudinid filiform mature spermatozoa. The ultrastructure of H. japonica spermatozoa is broadly similar to that already described for Haemadipsa zeylanica. The sperm has an anterior and a posterior acrosome, an elongated nucleus with two different morphological regions (an apical corkscrew-shaped region and a basal twisted column-shaped region), a single straight mitochondrion (midpiece) enclosed by a sheath of electron-dense material, and a flagellum with a prominent central sheath arrangement followed by a tapering appendage. A comparison with the previously described spermatozoa from other Clitellata species reveals that the greatest resemblance is to Hirudiniformes.