COMPARATIVE SPERMATOLOGY OF PROTURA AND ITS SIGNIFICANCE ON PROTURAN SYSTEMATICS

A comparative study on the ultrastructure of the spermatozoa of 20 spe cies of Protura belonging to 16 genera and 8 families was conducted. T he most remarkable characteristics are the unexpected diversity of the spermatozoa, both in shape and fine structure. In general they can be grouped into two main categories: long flagellate spermatozoa and sho rt aflagellate ones. Accordingly two sperm evolutionary lines of the s permatozoa were obtained: one trends towards the complicated acrosome structure and the increased number of axonemal doublets, and the other line is to shorten cell form and simplify sperm structure. The result s indicate that the spermatozoa of Hesperentomon may be the primitive type, and the spermatozoa of Eosentomids probably represent the most e volved type. A sperm evolutionary tree was drawn according to the apom orphies of proturan spermatozoa. The phylogenetic position of Protura was also discussed.