Morphology of the reproductive system and spermatozoa of Mesodasys adenotubulatus (Gastrotricha: Macrodasyida) |
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Authors: | E Fregni M Balsamo M Ferraguti |
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Institution: | (1) Dipartimento di Biologia Animale, Università di Modena e Reggio Emilia, via Università 4, I-41100 Modena, Italy, IT;(2) Istituto di Scienze Morfologiche, Università di Urbino, via Oddi 21, I-61029 Urbino, Italy, IT;(3) Dipartimento di Biologia, Università di Milano, via Celoria 26, I-20133 Milano, Italy, IT |
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Abstract: | Mesodasys adenotubulatus Hummon, Todaro and Tongiorgi 1993 is a simultaneous hermaphrodite. Two club-shaped testes extend along the sides of the anterior
intestine and show spermatogenetic stages maturing in a caudo-cephalic and centripetal direction. Sperm ducts join together
dorsally to the intestine before opening into a pear-like caudal organ. An unpaired, dorsal ovary lies anteriorly to the confluence
of sperm ducts. Oocytes mature in a caudo-cephalic direction; no oviduct nor female pore is present. The spermatozoa are fusiform,
with a very short tail. The anterior end of the sperm is a small, conic hood which corresponds to the acrosome. The following,
spindle-shaped corkscrew region contains a nuclear helix surrounding a central axis made of a single, giant mitochondrion.
The 9+2 axoneme is enclosed by a bilayered, obliquely striated cylinder only in the proximal tract. The morphology of the
reproductive system and spermatozoa of Mesodasys species is discussed, and the hypothesis of hypodermic impregnation in this genus is supported.
Received: 20 November 1998 / Accepted: 6 July 1999 |
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