water flea


: any of various small active dark or brightly colored aquatic crustaceans (such as a daphnia or cyclops)

Examples of water flea in a Sentence

Recent Examples on the Web In 2019, the biologists finally arrived at the optimal formula of mysid shrimp, water fleas and blood worms. Alexander Nazaryan, New York Times, 9 May 2024 Birdseed and the plants that attract songbirds aren’t a big draw for waterfowl, as most prefer beetles, snails, water fleas and other insects found on the edges of lakes and ponds. Renee Elder, Charlotte Observer, 31 Jan. 2024 To test for some of the potential adverse effects of these plastics, the researchers exposed a model organism called a water flea, or Daphnia, to different concentrations of the microplastics leached from the tea bags. Anna Funk, Discover Magazine, 26 Sep. 2019 Not bad for a water flea. Andrew Moseman, Discover Magazine, 4 Feb. 2011 Staring out of your screen is the eye of a water flea, a largely transparent crustacean that can reach half an inch in length. Discover Magazine, 21 Feb. 2012 But this one is special: The genome of the water flea contains a staggering 30,907 genes—the most ever seen in an animal, and about 8,000 more than humans have. Andrew Moseman, Discover Magazine, 4 Feb. 2011 Species like the fishhook water flea and the bloody red shrimp — which could be even worse than invasive carp. Juanpablo Ramirez-Franco, Journal Sentinel, 26 Aug. 2022 The next year, in 1982, overseas ships were blamed for bringing into the lakes the spiny water flea that has ravaged native zooplankton and the little fish that depend upon them. Dan Egan, jsonline.com, 2 Sep. 2021

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'water flea.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1687, in the meaning defined above

Time Traveler
The first known use of water flea was in 1687

Dictionary Entries Near water flea

Cite this Entry

“Water flea.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/water%20flea. Accessed 13 Jun. 2024.

Kids Definition

water flea

: any of various small active dark or brightly colored freshwater crustaceans (as a daphnia)

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