Viable algae released by the seastar Dermasteriasimbricata feeding on the symbiotic sea anemone Anthopleura elegantissima
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Echinoderms are major predators of anemones in temperate ecosystems. The fate of two algae, zooxanthellae and zoochlorellae, after their host anemone (Anthopleura elegantissima Brandt) was consumed by the leather star Dermasterias imbricata Grube was determined in experiments conducted in July and August 2004. Productivity, photosynthetic pigments, and mitotic index (percent of cells dividing) were used as indicators of algal health; algae released after leather stars consumed their host were compared with algae freshly isolated from anemones. Two types of waste products contained algae: pellets resulting from extraoral digestion, and feces. Zooxanthellae and zoochlorellae isolated from these waste products were photosynthetic, although to different extents. For algae from feces and pellets, light-saturated photosynthetic rates (Pmax) were 85 and 13%, respectively, of Pmax of freshly isolated zooxanthellae; and were 20 and 46%, respectively, for zoochlorellae. The photosynthetic pigments and mitotic index (percent of dividing cells) were not altered by the feeding activities of the leather star. These results show that algae released by seastar predation on their hosts remain viable, and are hence available for establishing symbioses in A. elegantissima and other potential hosts.
KeywordsMitotic Index Waste Product Photosynthetic Pigment Symbiotic Alga Host Anemone
This study was supported by NSF REU award OCE 0097190 to Western Washington University. We thank David Secord for arranging the loan of seastars from Friday Harbor Laboratories and for his comments on this work. Preparation of the manuscript took place while one of us (GMP) served in a position at the National Science Foundation. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the view of the National Science Foundation.
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