200 Years. 200 Stories. Story 149: “The Largest Freshwater Diatom ”

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light micrograph of Didymosphenia geminata

The Largest Freshwater Diatom

Last but certainly not least in our Three Weeks Behind the Scenes is an image of the largest freshwater diatom. The Academy’s Diatom Herbarium, one of the two largest in the world, is a primary source of taxonomic and ecological information. It includes approximately 220,000 slides, of which about 5,000 are types. Materials include fossil and recent diatoms collected from fresh, brackish, and marine habitats. Recently confirmed in the Delaware River and occurring in various parts of the world, Didymosphenia geminata is the largest freshwater diatom. This invasive species is usually common in clean, cold, fast-flowing rivers. The live diatom pictured is from a sample now stored in the Academy’s Diatom Herbarium.

Learn more about the Academy’s diatom research.

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