Copepods meaning “oar-feet” are a group of small crustaceans found in the sea
The body of an amphipod is divided into 13 segments
Amphipods are typically less than 10 millimeters
Mature females bear a marsupium, or brood pouch, which holds her eggs while they are fertilized and until the young are ready to hatch
Around 7,000 species of amphipods have so far been described
Most amphipods are detritivores or scavengers with some being grazers of algae, omnivores on small insects and crustaceans. Food is grasped with the front two pairs of legs which are armed with large claws
The name Amphipoda comes, via the New Latin amphipoda, from the Greek roots meaning different foot, in reference to the two kinds of legs that amphipods possess.
Copepods are sometimes used as bioindicators-Biological indicators are species used to monitor the health of an environment or ecosystem. An example of such a group are the copepods and other small water crustaceans present in many water bodies. Such organisms are monitored for changes (biochemical, physiological, or behavioral) that may indicate a problem within their ecosystem.
The copepod is typically 1 to 2 millimeters
Copepods typically have a short, cylindrical body, with a rounded or beaked head. The head is fused with the first one or two thoracic segments, while the remainder of the thorax has from three to five segments, each with limbs.
Because of their small size, copepods have no need of any heart or circulatory system
Many benthic copepods eat organic detritus or the bacteria that grow in it, and their mouth parts are adapted for scraping
They are usually the dominant members of the zooplankton, and are major food organisms for small fish, whales, seabirds and other crustaceans such as krill in the ocean
Live copepods are used in the saltwater aquarium hobby as a food source and are generally considered beneficial in most reef tanks. They are scavengers and also may feed on nuisance algae