nucleus & arm

Description:

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. Multiple nuclei and nucleating sites for the arms line at the interface between the inner and outer regions of cytoplasm. This micrograph shows an axoneme and a nucleus - which has a round nucleolus at its centre. Differential interference contrast.