Spawning and development in Osedax boneworms (Siboglinidae, Annelida)
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ORIGINAL PAPER
Spawning and development in Osedax boneworms (Siboglinidae, Annelida) Greg W. Rouse · Nerida G. Wilson · Shana K. GoVredi · Shannon B. Johnson · Tracey Smart · Chad Widmer · Craig M. Young · Robert C. Vrijenhoek
Received: 10 September 2008 / Accepted: 14 November 2008 / Published online: 10 December 2008 © Springer-Verlag 2008
Abstract We report observations on spawning and early development in bone-eating worms of the genus Osedax. Individual females of Osedax rubiplumus were observed at 1820 m depth freely spawning hundreds of oocytes, and females of an undescribed species, Osedax “orange collar”, were observed spawning in laboratory aquaria. Cytological and molecular analysis of the spawned oocytes of two Osedax species revealed no evidence for the bacterial endosymbionts that the female worms require for their nutrition, suggesting that the bacteria must be acquired later from the environment, as they are in other siboglinids. Individual O. “orange collar” females released an average of
Communicated by M. Byrne. Electronic supplementary material The online version of this article (doi:10.1007/s00227-008-1091-z) contains supplementary material, which is available to authorized users. G. W. Rouse (&) · N. G. Wilson Scripps Institution of Oceanography, UCSD, La Jolla, CA 92093, USA e-mail: [email protected] S. K. GoVredi California Institute of Technology, Pasadena, CA 91125, USA S. B. Johnson · R. C. Vrijenhoek Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA T. Smart · C. M. Young Oregon Institute of Marine Biology, University of Oregon, Charleston, OR 97420, USA C. Widmer Monterey Bay Aquarium, Monterey, CA 93940, USA
335 (§130) eggs per day, but the number of oocytes spawned per day varied greatly, suggesting that not all the females spawned daily. Fertilization rates of the spawned oocytes varied from 0 to 100%, though most females showed nearly 100% fertilization rates. Oocytes spawned in the laboratory at 4–6°C were negatively buoyant. If fertilized, these oocytes extruded polar bodies and then after at least four hours cleaved unequally. Subsequent cleavages occurred in a spiral pattern at roughly 2-h intervals, resulting in free-swimming trochophore larvae after 24 h. These lecithotrophic trochophores swam for 9–16 days before settling with several hooked chaetae, similar to those of dwarf Osedax males. The larval life span of the Osedax species studied in the laboratory appears to be shorter than in closely related Vestimentifera. Osedax rubiplumus, on the other hand, has much larger oocytes and so may have greater dispersal potential than these other Osedax species. The high fecundity and apparently continuous reproduction of Osedax boneworms permits the opportunistic exploitation of sunken vertebrate bones.
Introduction Though only recently discovered, bone-eating annelids of the genus Osedax (Polychaeta: Siboglindae) are now known to occur worldwide (Rouse et al. 2004; Glover et al. 2005; Fujikura et al. 2006; Braby et al. 2007; Vrijenhoek et al. 2008a). Osedax fe
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