#mysida

A few species of mysid, mostly in the subfamily Heteromysinae, are commensal (a form of symbiosis in which members of one species gain benefits while those of the other species neither benefit nor are harmed) and are associated with sea anemones and hermit crabs.

The species Mysidium integrum has a mutualistic relationship with Longfin Damselfish (Stegastes diencaeus), with the mysid providing nutrients for the algae farms the fish tends to and feeds on, and the fish providing protection from predators. The interaction has been described as a form of domestication, with the fish caring for the crustaceans as livestock.

The freshwater species of the genus Mysis have been referred to as “glacial relicts”, species whose range was once much wider in previous epochs. Mysis relicta (image 3) is a freshwater species now relegated to boreal lakes of Northern Europe, though it is also present in the Baltic Sea. The North American lakes, including the Great Lakes, are inhabited by Mysis diluviana. Various species of Mysis are found in lakes of the South Swedish highlands, like Lake Sommen, that were never connected to the sea or the Baltic Ice Lake. This have led to theories that claim a natural lock system existed in the area during the Younger Dryas (12,900 to 11,700 years Before Present).

Possibly the cutest mysids, species of the genus Idiomysis are just few millimeters in length, with a rounded cephalothorax and a characteristic curled-up abdomen (image 2 and gif). When compared with other mysids, Idiomysis species have short antennae, relatively big eyes and a small, usually unarmed telson. They live in small groups of 5 to more than 40 individuals, which hover over the sea bottom, looking like a swarm of tiny orbs with big eyes.

The Chameleon Shrimp (Praunus flexuosus) (image 1) is named for its highly variable coloration, ranging from brown or red to green.

Male Mysids have a pair of long penises (penii?), which are both inserted into the female’s marsupium during sex. His release of sperm into the marsupium stimulates the female, who releases eggs usually within an hour. The young are fertilized and retained within the marsupium until they emerge, as miniature adults. Follow for more Penis Facts.

Mysids form an important part of the diet of many fish, such as as shad (family Alosidae) and flounder (suborder Pleuronectoidei).