Gametogenesis, spawning behavior, and early development in the “iceworm”Hesiocaeca methanicola (Polychaeta: Hesionidae) from methane hydrates in the Gulf of Mexico |
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Authors: | K J Eckelbarger C M Young E Ramirez Llodra S Brooke P Tyler |
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Institution: | (1) Darling Marine Center, University of Maine, 193 Clark's Cove Rd., Walpole, ME 04573, USA e-mail: kevine@maine.edu Fax: +1-207-5633119, US;(2) Harbor Branch Oceanographic Institution, 5600 U.S. 1 North, Ft. Pierce, FL 34946, USA, US;(3) Department of Oceanography, The University, Southampton SO9 5NH, United Kingdom, GB |
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Abstract: | Gametogenesis, spawning behavior, and early development have been described in the methane-seep polychaete Hesiocaecamethanicola Desbruyères and Toulmond, 1998, the first documentation of the reproductive biology of any cold-seep polychaete species.
The worms were collected at the Green Canyon site in the Gulf of Mexico (27°44.77N; 91°13.33W) in August 1997. The gonads
are situated in the neuropodia in association with an intraepithelial capillary system. Oogenesis is intraovarian, with oocytes
remaining in the ovary until late vitellogenesis when they are released into the coelom for final growth and differentiation.
Vitellogenesis involves both autosynthetic and heterosynthetic processes and, along with ovarian structure, suggests a relatively
slow process of egg formation. Sperm differentiation is intertesticular until early spermiogenesis, when spermatid tetrads
complete development in the coelom. The mature spermatozoon is an ect-aquasperm consisting of a tapering, digitate acrosome,
a spherical nucleus, a midpiece containing from six to eight mitochondria and glycogen stores, and two centrioles associated
with the flagellum. Both sexes undergo broadcast spawning, but the males spawn exclusively through the anus, a behavior previously
unknown in polychaetes. Artificial fertilization resulted in spiral cleavage and development to the trochophore stage. Oocyte
size-frequency analysis of adult females indicates a wide range of oocyte sizes and vitellogenic stages, suggesting that asynchronous
gametogenesis occurs.
Received: 13 July 2000 / Accepted: 29 November 2000 |
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