Living radiolarian feeding mechanisms: new light on past marine ecosystems
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Environmentally controlled studies on living radiolarians, especially on their feeding mechanisms are rare. In the same way, feeding behaviours of fossil radiolarians are poorly known. In this work, techniques for living radiolarian research, including plankton sampling at sea, observations using different types of microscopes, and laboratory culture, are introduced. Light microscope, epifluorescence microscope, and confocal laser scanning microscope images of selected radiolarian species are presented. Four types of feeding behaviour which correspond well to skeletal morphology are recognized and discussed. Multi-segmented nassellarians, represented by Eucyrtidium, Pterocorys, and Spirocyrtis, take relatively large prey, including ciliates and flagellates. Some other nassellarians, e.g. Pseudocubus and Arachnocorallium, are advantageous in collecting tiny prey including microflagellates and bacteria. Solitary spumellarians, represented by Diplosphaera, Spongosphaera, and Spongaster, also gather tiny prey. Colonial radiolarians such as Collozoum and Buccinosphaera seem to live exclusively on symbiotic algae. The wide variation in feeding behaviour means that radiolarians occupy several kinds of ecological niches in marine environments. Assuming that the radiolarian skeletal morphology indicates their feeding strategy, living forms can give some light on the feeding mechanisms of similar Mesozoic forms. By contrast, the unique curved conical skeleton of the Paleozoic Albaillellaria, unknown after the end-Permian mass extinction, suggests a different feeding behaviour.
Keywords:Radiolaria culture feeding behaviour prey past marine ecosystems end-Permian extinction
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