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Daphnia lumholtzi, a native to tropical and subtropical lakes in E. Africa, E. Australia and India, that has invaded the Southern and midwestern U.S. (since 1990), perhaps originating with imported Nile perch. D. lumholtzi is ~3-4 mm long and has very long helmet and tailspines. Photo from old ASLO slide collection; taken by R. Sterner; scanned by K.L. Schulz.