Any member of the order Isopoda. Isopods are
segmented crustaceans, the best known
of which are woodlice, pill bugs, sow bugs, and other land-dwelling species.
In caves, aquatic isopods are often studied because many are troglobitic
and depend on caves for survival. Most isopods are small; however, there
are about nine species of so-called giant isopods in the genus Bathynomus.