Ac·​ti·​no·​sphae·​ri·​um | \¦ak-tə-(ˌ)nō-ˈsfir-ē-əm\

Definition of Actinosphaerium 

: a genus of large freshwater protozoans (order Heliozoa)

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First Known Use of Actinosphaerium

1879, in the meaning defined above

History and Etymology for Actinosphaerium

New Latin, from actin- + Greek sphairion little ball, diminutive of sphaira ball, sphere

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The first known use of Actinosphaerium was in 1879

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