Abstract
Chaetognata (arrow worms) are a hermaphroditic phylum. The male reproductive tract, consisting of paired testes, vasa deferentia and seminal vesicles, is located in the caudal region of the body. Within the seminal vesicles of mature organisms, the filiform spermatozoa are packed into aggregates which are of the same size and shapaas the seminal vesicles. Emission occurs by rupture of the vesicle wall. In the literature (reviewed by Reeve and Cosper 1975), the sperm aggregates of chaetognaths, such as Sagitta or Spadella, are invariably referred to as spermatophores (rather than spermatozeugmata). It seems that in some species at any rate, following discharge from the spermatophore, the spermatozoa can be used for both self-fertilization and cross-fertilization. Ghirardelli (1968), in his extensive study of spermatophores in the benthic genus Spadella, described crossfertilization as a process in which a spermatophore from each individual is first placed on the neck of the partner and later, after the posterior portion of a spermatophore had dissolved, the spermatozoa pass into the seminal receptacles. From there they migrate to the ovary and fertilize the eggs which are still positioned in the gonad. In some chaetognaths, the seminal vesicles are equipped with special serrated structures which separate together with the spermatophore. Such structures, tubular in shape, are particularly prominent on spermatophores of Eukrohnia, and they are believed to act as a kind of copulatory device that facilitates the attachment of the spermatophore to the female genital orifice.
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© 1984 Springer-Verlag Berlin Heidelberg
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Mann, T. (1984). Chaetognatha and Pogonophora. In: Spermatophores. Zoophysiology, vol 15. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-82308-4_9
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DOI: https://doi.org/10.1007/978-3-642-82308-4_9
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-642-82310-7
Online ISBN: 978-3-642-82308-4
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