The other six pairs of thoracic appendages are biramous (branching) limbs known as pereopods, and are used for swimming, as well as for wafting water towards the maxillipeds for feeding.

This brood pouch is enclosed by the large, flexible oostegites, bristly flaps which extend from the basal segments of the pereopods and which form the floor of a chamber roofed by the animal's sternum.

These help the animal orient itself in the water and are clearly seen as circular vesicles: together with the pouch the statocysts are often used as features that distinguish mysids from other shrimp-like organisms.

[2] Some benthic species, especially members of the subfamily Erythropinae, have been observed feeding on small particles which they collected by grooming the surfaces of their bodies and legs.

Here they are fertilised and retained, development of the embryos in the brood pouch being direct with the young hatching from the eggs as miniature adults.

[2] The size of a mysid brood generally correlates with body length and environmental factors such as density and food availability.

[11] The young are released soon afterwards, and although their numbers are usually low, the short reproductive cycle of mysid adults means a new brood can be produced every four to seven days.

[3][11][12] Some species of mysids are easy to culture on a large scale in the laboratory as they are highly adaptive, and can tolerate a wide range of conditions.

[13] In flow-through systems, juvenile mysids are continuously separated from the adult brood stock in order to reduce mortality due to cannibalism.

[9] Artemia (brine shrimp) juveniles (incubated for 24 hours) are the most common food in mysid cultures, sometimes enriched with highly unsaturated fatty acids to increase their nutritional value.

They are often fed to cephalopods, fish larvae, and commercial farmed shrimp due to their small size and low cost.

[9][14][15][16] Their high protein and fat content also makes them a good alternative to live enriched Artemia when feeding juveniles (especially those that are difficult to maintain such as young seahorses) and other small fauna.

Although in many respects mysids appear similar to some shrimps, the main characteristic separating them from the superorder Eucarida is their lack of free-swimming larvae.

[5] Traditionally, Mysida were united with another, externally similar group of pelagic crustaceans, the Lophogastrida, into a broader order Mysidacea, but that classification is generally abandoned at present.