Animal Zooplankton











Zooplankton are the animal members of the plankton community.  In Chesapeake Bay, the zooplankton can be composed of rotifers and barnacle nauplii on the smallest end of the size scale (less than 1/10th of a millimeter for some of the smallest species), Copepods and Cladocerans at the intermediate or mesozooplankton size scale, on up to macrozooplankton that include the ctenophores and true jellyfish, the Cnidarians.  Copepods are clearly segmented with generally elongate body divided into a head, thorax and abdomen.

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Copepods are often the most abundant mesozooplankters in the main stem of the Bay during the year but copepods as a group can be found in fresh and salt water areas. The species Paracyclops timbriatus (top) and Cyclops vernalis (right) pictured here are filter feeders. Adult copepods range in size from approximately 0.4 mm to about 2.5 mm in length. Some copepods are filter feeders that use their antennae to produce a current that draws food to their mouthparts. Other types of copepods exhibit raptorial feeding behavior and seize prey with their mouthparts.






The Cladocerans have a distinct head and a bivalve carapace. Most cladocerans feed by filtering food that passes through the valves by the action of their legs. Adult cladocerans generally range in size from 0.1 mm to 4 mm. Cladocerans also occupy fresh and saltwater and can dominate the plankton community in freshwater areas in the tidal Bay during some seasons. Two species found in the Bay are pictured, Alona costata (right) and Scapholeberis kingi (above left).

*Pictures provided by Versar, Inc.

For more information, please contact Peter Tango at (410) 260-8651.

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