The aberrant spermatogenesis of the Haplothrips simplex (Buffa) (Thysanoptera): ultrastructural study

The aberrant spermatogenesis of the haploid insect Haplothrips simplex (Thysanoptera) is described. The process, which occurs in the pupal instars, is characterized by two mitotic divisions, the second of which gives rise to two different-sized spermatids: the larger spermatids have a nucleus with diffuse chromatin and proceed into spermiogenesis, while the small spermatids have pycnotic nuclei and degenerate. Both types of spermatids contain two centrioles parallely rather than orthogonally oriented. The occurrence of two centrioles supports a close relationship between Thysanoptera and Phthyraptera. Before the beginning of spermiogenesis, however, the functional spermatids show the unusual presence of a third parallel centriole which is formed by the duplication of one of the two pre-existing centrioles.