Ultrastructure and Development of the Ooecial Walls in Some Calloporid Bryozoans (Gymnolaemata: Cheilostomata) |
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| Authors: | Andrew Nickolaevitch Ostrovsky Priska Schfer Dennis Paul Gordon |
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| Institution: | aDepartment of Invertebrate Zoology, Faculty of Biology & Soil Science, St. Petersburg State University, St. Petersburg, Russia;bInstitut für Geowissenschaften, Christian-Albrechts-Universität zu Kiel, Kiel, Germany;cNational Institute of Water & Atmospheric Research, Wellington, New Zealand |
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| Abstract: | In the brood chambers (ovicells) of six calloporid cheilostomes studied each skeletal wall consists of four calcified layers: (1) a very thin superficial layer of planar spherulitic crystallites, (2) an upper (outer) layer with wall-perpendicular prismatic ultrastructure, (3) an intermediate lamellar layer, and (4) a lower (inner) wall-perpendicular prismatic layer. Comparative studies of both the ovicell wall ultrastructure and early ovicell formation showed a hypothetical opportunity for evolving complex (multilayered) skeletal walls by fusion of the initially separated gymnocystal and cryptocystal calcifications in Cheilostomata. In two species studied, a bilobate pattern in the final stage of the formation of the ooecial roof was encountered in specimens with the cuticle preserved. A possible explanation to this finding is discussed – the bilobate pattern is suggestive of the hypothetical origin of the brood chamber from (1) two flattened spines, or (2) reduction in spine number of an originally multispinous ovicell. |
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| Keywords: | Ovicells Callopora Tegella Crassimarginatella Bryozoa |
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