Ultrastructural analysis of sperm from the genus Idarnes(Hymenoptera:Chalcidoidea,Sycophaginae)

In this study,the sperm ultrastructure of three species of Idarnes genus was investigated using light and transmission electron microscopy.Spermatozoon morphology of the three species was similar to that of most Chalcidoidea,with helicoidally twisted nucleus and flagellum.The head region consists of an acrosome and a nucleus;the nucleus-flagellum transition region characterized by the presence of mitochondrial derivatives and the centriolar adjunct;a flagellum region,which includes the axoneme with microtubular arrangement 9+9+2 and two mitochondrial derivatives.However,the sperm of these three species exhibit features that discriminate one species from each other:(1)only one species,Idarnes sp.2(carme group)exhibited an extracellular sheath surrounding the anterior portion of the nucleus,which extends to the anterior region of the flagellum,but it did not present filaments;(2)the acrosome in the three species was quite different,Idarnes sp.1 and Idarnes sp.2(carme group)has two compartments(acrosomal and subacrosomal vesicles)while Idarnes sp.3(flavicollis group)has a third compartment(perforatorium);(3)the centriolar adjunct elongated and its location among the mitochondrial derivatives is similar for the three species analyzed;(4)mitochondrial derivatives differ between the species,with triangular(Idarnes sp.1 and sp.3)and elongated or flat shaped(Idarnes sp.2)appearance.These data shows that sperm structure may differ within the same genus and confirms the potential of these cells in phylogenetic and taxonomic analyses in the Chalcidoidea superfamily,as well as in Hymenoptera in general.

Vlouse sperm acquire a new structure on the apical hoo Juring epididymal maturation

Spermatozoa emerging from the testis undergo a maturation process in the epididymis during which they change morphologically, biochemically and physiologically to gain motility and the ability to fertilize ova. We examined mouse epididymal sperm with immunostaining and transmission electron microscopy （EM） and identified a previously unknown structure on the apical hook. The structure has a coiled configuration around 11 nm in thickness and is present at the tip of each corner of the triangular-rod shaped perforatorium. Surveying sperm isolated from various regions of the epididymis indicated that mouse sperm acquire the hook rim （HR） structure during its passage through the proximal two-thirds of the caput epididymidis. The structure withstands vigorous sonication and harsh chemical treatments and remains intact after the acrosome reaction. Its location and sturdiness suggest a function in protecting the apical hook from mechanical wear during fertilization. Our EM images of epididymal sperm also revealed additional novel structures as well as lateral asymmetry of the sperm head, indicating that mouse sperm head has a structure more complex than previously recognized.