Substrate choice and settlement preferences of planula larvae of five Scyphozoa (Cnidaria) from German Bight,North Sea |
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Authors: | Sabine Holst Gerhard Jarms |
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Institution: | 1.Universit?t Hamburg, Biozentrum Grindel und Zoologisches Museum,Hamburg,Germany |
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Abstract: | The settlement behaviour of planula larvae and their development to young polyps was investigated in laboratory experiments
in five scyphozoan species Aurelia aurita (L.), Cyanea capillata (L.), Cyanea lamarckii Péron and Leseur, Chrysaora hysoscella (L.), and Rhizostoma octopus (L.)]. The undersides of settling plates were strongly preferred for settlement. Shells, the only natural substrate type
offered, were less attractive than artificial substrates (concrete, machined wood, polyethylene, and glass). The advantages
of colonization of substrate undersides for survival and reproduction of polyps are discussed. It is supposed that the increase
of artificial substrates in our seas, due to marine litter pollution and submarine building activities, enlarge the areas
of distribution of scyphozoan polyps, in coastal as well as in off-shore regions. Subsequent increases in ephyra production
by polyps are probably one reason for the increase in mass occurrences of jellyfish recognized worldwide during the last few
decades. It is suggested that the early developmental stages in the cnidarian life cycle, the planula larvae, and the polyps,
play the key role in the development of jellyfish outbursts. |
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