Structure of spermatodesms of Orthoptera Tettigonioidea.

Examination of spermatodesms collected from the male and female genital tracts of numerous Orthoptera Tettigonioidea revealed an overall morphological and ultrastructural organization that is generally similar in individuals of the same sex but considerably different between males and females of even the same species. In the male genital tracts each spermatodesm is composed of a limited number of spermatozoa whose nuclei and acrosomes are covered by a mucous cap. The spermatozoa inside each bundle are mainly arranged in parallel rows and are always distinctly separate. The number of spermatozoa per spermatodesm may vary within the same individual although it does not seem to exceed a maximum value that we could only determine exactly in Tettigoniidae species. The most characteristic feature of spermatozoa of all the species examined is a conspicuous elongation of the plasma membrane in the acrosomal region that is not present in the female genital tracts. In addition, spermatodesms from females are composed of highly numerous tightly packed spermatozoa that are linked together via the acrosomal region. This characteristic of spermatodesms, never previously reported in other insect species, would involve their reorganization during transfer from the male to the female genital tracts and would seem to take place in the spermatophore. The probable role of spermatodesms in the reproductive physiology of Tettigonioidea might be related to the degree of maturity of the sex cells transferred to the female; the reorganization of the spermatozoa out of the male genital tracts seems to support this hypothesis.