The Flagellum of the Shortest Spermatozoon in the Animal Kingdom: Elongation and Shortening of the Axoneme in the Process of Spermiogenesis of the Parasitic Wasp Cotesia Congregata

Uzbekov, R.; Garanina, A.; Burlaud-Gaillard, J.; Bressac, C.

Авторы: Uzbekov R., Anastasiia Garanina, Julien Burlaud-Gaillard, Christophe Bressac
Сборник: Flagella and Сilia. Types, Structure and Functions. Editor Rustem E. Uzbekov
Серия: CELL BIOLOGY RESEARCH PROGRESS
Глава в коллективной монографии
Год издания: 2018
Место издания: Nova Science Publishers, Inc New York
Первая страница: 83
Последняя страница: 108
Аннотация: Flagella serve as the movement apparatus of sperm. However, the length of the flagellum varies widely in animals of different species; extremes are observed in insects with the longest (close to 6 cm) and the shortest (less than 7 μm). In the present work, using light microscopy, scanning and transmission electron microscopy on serial ultrathin sections we have in detail characterized the process of flagellum development during spermiogenesis of the parasitic wasp Cotesia congregata, the animal having the shortest sperm. In an early spermatid with round nucleus centrosome contains two centrioles. Later, one of the two centrioles begins the formation of flagellum. Parallel to this, the second centriole separates and migrates to the central part of the cyst syncytium and can form a primary cilium there. The length of the flagellum in the spermatids with a long nucleus reaches 5 microns and persists on this level up to the spermatid, with a condensed chromatin nucleus. At this stage, the length of the nucleus in the spermatids decreases more than 3-fold. At the final stage of spermiogenesis, during transition from spermatid with condensed chromatin nucleus to a mature spermatozoon, a dramatic more than 2-fold decrease in the length of the flagellum also occurs. The flagellum becomes shorter than the sperm nucleus. The described experimental model can be used to study the mechanisms of controlled shortening of the axoneme. The study of the fine structure of the flagellum on ultrathin cross sections showed that when a spermatid passes to a mature spermatozoon, the centriole in it is replaced by a structure that does not contain microtubules. A structure with very similar morphology was discovered by us earlier in the study of the development of another parasitic wasp Anisopteromalus calandrae in somatic cells of larvae and was called - the “cogwheel structure.” Despite the absence of microtubules, the “cogwheel structure” performed in the cells the functions of centrioles. Summarizing the data of our two works, we can hypotheses that the spermatozoon of parasitic wasps introduces into the zygote a “cogwheel structure” in diploid female insects. In haploid male insects “cogwheel structure” appears de novo, like centrioles during mouse development. This structure is duplicated and distributed over the daughter cells and only when the insect passes to the stage of the pupa it is transformed into a “normal” centriole containing triplets of microtubules. Such a transformation in somatic cells is obviously associated with a reorganization of the genetic program associated with the need to form cilia in somatic cells, and spermatozoa in the male sex cells.
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The Flagellum of the Shortest Spermatozoon in the Animal Kingdom: Elongation and Shortening of the Axoneme in the Process of Spermiogenesis of the Parasitic Wasp Cotesia Congregataстатья

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