Abstract
The spermatozoa of two species supposed to be basal to Gastrotricha Chaetonotida, Neodasys ciritus and Musellifer delamarei, were studied in order to supply further elements to the understanding of sperm evolution in Chaetonotida, a group in which a fully parthenogenetic reproduction is dominant. Two considerably different sperm patterns were found: the spermatozoon of N. ciritus has a simple, conical acrosome, a short, condensed nucleus, few conventional mitochondria randomly arranged along the sperm head, and a 9×2+2 flagellum perpendicular to the sperm major axis. The spermatozoon of M. delamarei is a filiform cell with a simple acrosome, a partially condensed nucleus, four mitochondria at the nuclear base, and a flagellum with a 9×2+2 axoneme and large accessory fibers. Some sperm features of M. delamarei are comparable to those of Xenotrichulidae, the only other Chaetonotida producing conventional spermatozoa, whereas the sperm of N. ciritus appears different from all the other patterns known among Gastrotricha, thus knowledge of it does not help in solving the problem of the discussed phylogenetic position of the genus.
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Acknowledgements
We would like to thank Mr. Silvio Cecchini (Facoltà di Scienze Matematiche, Fisiche e Naturali, Università di Urbino) for his valuable help in elaborating and assembling the photographic TEM material and Mr. Oliviero Rusciadelli for his technical help with electron microscopes. We are also grateful to Ms Laura Valenti for accurate ink drawings. We are indebted to the referees for their helpful comments. This research was supported by grants from MIUR (Rome) to M.B. and M.F. (Cofin Projects 2000 'Evoluzione molecolare e marcatori di processi di filogenesi e di adattamento' and 2002 'Evoluzione molecolare e marcatori morfologici nello studio dei rapporti filogenetici e meccanismi adattativi in taxa chiave di protisti ed invertebrati') and to M.B. (Scientific Research Funds).
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Guidi, L., Marotta, R., Pierboni, L. et al. Comparative sperm ultrastructure of Neodasys ciritus and Musellifer delamarei, two species considered to be basal among Chaetonotida (Gastrotricha). Zoomorphology 122, 135–143 (2003). https://doi.org/10.1007/s00435-003-0079-y
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DOI: https://doi.org/10.1007/s00435-003-0079-y