New data on the aberrant spermatogenesis of Collembola

Aberrant spermatogenesis in the two species Stenognathellus denisi (Katiannidae) and Sminthurides aquaticus (Sminthurididae) is described. An ultrastructural study of spermatogenesis in these species has allowed us to reveal the presence of two types of secondary spermatocytes; one with a normal appearance, the other one is characterized by a small size, a reduced cytoplasm (showing only two centrioles), and a nucleus with very condensed chromatin. These latter aberrant cells are not able to perform the second meiotic division and will degenerate. This finding allows us to extend the identification of an aberrant spermatogenesis and the consequent postzygotic sex determination to two more families of Symphypleona.