Reproduction in Anthelia glauca (Octocorallia: Xeniidae). II. Transmission of algal symbionts during planular brooding |
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Authors: | Y Benayahu M H Schleyer |
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Institution: | (1) Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel, IL;(2) Oceanographic Research Institute, P.O. Box 10712, Marine Parade 4056, Durban, Republic of South Africa, ZA |
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Abstract: | The soft coral Anthelia glauca Lamarck, 1816, of the family Xeniidae, is found on the reefs of KwaZulu-Natal, South Africa. Its gastrodermal cells contain
numerous endosymbiotic unicellular algae (zooxanthellae). A. glauca is a gonochoric species that simultaneously broods its planulae within the pharyngeal cavity of the polyps. Symbiotic algae
appear with zygote formation within the pharynx, embedded in amorphous material. The algal cells adhere to the ciliated ectodermal
surface of immature planulae and are most probably endocytosed by them. Zooxanthellae are translocated towards the basal part
of the ectoderm. Gaps are subsequently opened in the mesoglea into which symbionts surrounded by ectodermally derived material,
including plasma membrane, pass. The basal membrane of endodermal cells disintegrates, and the algae bulge into spaces formed
in the underlying endoderm. Throughout the process, each zooxanthella resides within a vacuolar membrane in the detached ectodermal
cytoplasm. The acquisition process is essentially one in which zooxanthellae are translocated from the pharyngeal cavity into
the ectoderm and then through the mesoglea into the endoderm, culminating in the final symbiotic state. The direct transmission
of symbiotic algae to the eggs or larvae probably provides the most efficient means whereby zooxanthellae are acquired by
the host progeny.
Received: 15 July 1997 / Accepted: 25 February 1998 |
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