Cumacea: Key to Families and References

No species of the Cumacea is known to be truly planktonic, most of their lives being spent on the sea bottom. Many species from shallow water, however, become pelagic at certain times, usually during the night, when the adult males especially leave the bottom and swim upwards. They may then be caught in tow-nets and in traps containing a  submerged light of low intensity (Fage, 1933; Sheard, 1941). Where they are attracted to a  light it is usually found that males greatly exceed females in number, and the species caught most abundantly are those with well developed eyes, particularly species of the Bodotriidae and the genera Nannastacus, Cumella, and Pseudocuma. In tow-nets used without illumination the disparity between the sexes of those captured is less apparent (Hale, 1952). It is not known whether there is any vertical migration among the species inhabiting deep water, and not all the species from shallow water have been caught above the bottom; however, since this may be merely a consequence of neglect of the group, all species for which records exist of capture in depths of less than 50 m. within the area dealt with are included in the keys.