Population
Actinosphaerium (act-in-o-sphere-ee-um) (=Echinosphaerium), one of the largest freshwater heliozoa, may measure up to 500 microns, often with outer layer being very vacuolated. This group photograph shows some of the variation in size. Multiple nuclei and nucleating sites for the arms line at the interface between the inner and outer regions of cytoplasm. Yellowy zones in the centre is some food being digested - these heliozoa can consume small metazoa. Dark ground illumination. This picture was taken by David Patterson and Aimlee Laderman of material collected from a freshwater Atantic white cedar swamp at Cumloden near Woods Hole in Massachusetts, USA in spring and summer, 2001. Image copyright: D. J. Patterson and Aimlee Ladermann, image used under license to MBL (micro*scope).
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Actinosphaerium eichhornii
From the collection
Cumloden, Massachusetts, USA
| Description of Actinosphaerium eichhornii: 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. |
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