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Copepods

Illustration of copepods from Ernst Haeckel.
Ernst Haeckel, Kunstformen der Natur / Biodiversity Heritage Library

Copepods are aquatic crustaceans found in every marine habitat, from surface waters to the deep sea. With over 13,000 described species, they are among the most abundant of all multicellular animals. About half are parasites; the rest are free-living and make up much of the ocean's zooplankton. Figures 6 and 7 are particularly intriguing, as they portray various ways that female copepods carry fertilized eggs in egg sacs attached to their bodies.