How small can water fleas and copepods be?

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crustacean The American lobster (*Homarus americanus*) is among the largest crustaceans.

Water fleas and copepods are both members of the subphylum Crustacea, which falls under the phylum Arthropoda. Both groups contain exceptionally small species:

Water fleas: While most species typically measure between 0.2 and 3.0 millimetres, some, such as those in the genus Alonella, can reach lengths of less than 0.25 millimetres (0.009 inch).12
Copepods: Most species range from 0.5 to 2 millimetres in length, though many are less than one millimetre long. The males of the species Sphaeronellopsis monothrix, which are parasitic on marine ostracods, are among the smallest known copepods, attaining lengths of only 0.11 millimetres.32