Description of Actinosphaerium eichhornii
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Actinosphaerium is a spherical naked actinophryid heliozoon with numerous small nuclei. Cell body 45 - 1000 microns. The cytoplasm always has a discrete peripheral layer of large vacuoles, and the nuclei occur at the inner boundary of this layer. Many arms, tapering from base to tip - axonemes terminate on the nuclei or electron-dense material near the nuclei. Several species are known, mostly freshwater and distributed world wide.