capitalized: a genus of small aquatic holotrichous ciliates that are much used in biological research
plural colpidia: a member of the genus Colpidium
borrowed from New Latin, from Greek kólpos "lap, bosom, fold in a garment" + New Latin -idium-idium
Genus name introduced by the German biologist Samuel Friedrich Stein (Friedrich von Stein, 1818-85) in Sitzungsberichte der königlichen böhmischen Gesellschaft der Wissenschaften in Prag, Jahrgang 1860 (Januar-Juni), "Naturwissenschaftliche-mathematische Section am 27. Februar 1860," p. 47. Stein's Colpidium is a renaming of Paramaecium colpoda; both the names Colpidium and colpoda, as well as the genus name Colpoda (see Colpoda), are presumably suggested by the fold in the side of the organism in which the oral groove is located.
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