UV2 Mysis Shrimp- Mysida are small, shrimp like crustaceans in the malacostracan superorder Peracarida. These opossum shrimps have a brood pouch or "marsupium" in females. The fact that the larvae are reared in this pouch and are not free-swimming characterizes the order. They are found in shallow and deep marine waters but they are also important in freshwater. They are filter feeders and omnivores that feed on algae, detritus and zooplankton. This is an important pattern on streams like the Frying Pan in Colorado due to the large reservoir above. Size 18.