The influence of UV radiation on number and ultrastructure of the endosymbiotic dinoflagellates in the sea anemoneCereus pedunculatus (Anthozoa: Actiniaria)

Autor: O. Sicken, Wilfried Westheide, K. Hannack, Paul Kestler
Rok vydání: 1998
Předmět:
Zdroj: Helgoländer Meeresuntersuchungen. 51:487-502
ISSN: 1438-3888
0174-3597
Popis: The sea anemoneCereus pedunculatus was artificially UV-irradiated to test the effect of UV-light on the number of endosymbiotic dinoflagellates in its gastrodermis and on their ultrastructure. Anemones were kept in the laboratory in a light: dark cycle (LD 12∶12; 13 W m−2) at 18 °C and briefly (2, 5 and 9 d) exposed to UV radiation at quasisolar intensities, 0.5 or 1 W m−2. Their tentacles were then examined in the electron microscope for qualitative and quantitative changes in the zooxanthellae. There was an intensity-dependent decrease in the number of symbionts, which in some cases were lost altogether (bleaching). Irradiated anemones contained a larger proportion of symbionts with ultrastructural abnormalities, namely diminished starch, some mitochondria with altered matrix and, in particular, characteristic changes in the chloroplasts; instead of being densely stacked, the thylakoids were spread apart and swollen at the ends of their membranes to form vesicle-like structures. Relatively large vesicles also appeared in the cytoplasm. The resulting enlargement of the whole dinoflagellate cell was documented morphometrically. Another intensity-dependent effect was a significant decrease in mitosis rate, established by counting dividing symbiont cells in TEM micrographs. *** DIRECT SUPPORT *** A03B6037 00006
Databáze: OpenAIRE
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