III. Protostomia
          IV. Ecdysozoa
            V. Arthropoda
               VI. Crustacea
                 VII. Malacostraca
                   VIII. Eumalacostraca
                     IX. Peracarida
                        X. Mysida
                           XI. Mysis
                             XII. relicta
(Taken from: Integrated Taxonomic Information System, 2005)
The Opossum Shrimp (Mysida)
Their common name opossum shrimp comes from the presence of brood pouch in females, where they carry their larvae which are not free-swimming. This crustacean is like the kangaroo of the sea!Â
They can be found in many types of aquatic environment, in freshwater and marine, deep sea, shallow coastal waters, lakes, rivers and underground waters. Mysids are utilized commercially in Japan, Southeast Asia, China and Korea, and can be found in different marine habitats such as Pelagic, Coastal and estuarine. Worldwide, there are 160 genera and over 1000 described species. (Porter 2016; Jones 2003)
       Map of stations in Southeast Asia where Mysid specimens were recorded (Sawamoto 2013)
Mysid Shrimp have mechanisms that help them in mating. In some species, receptive females release pheromones in the water to attract males. Mating takes place during copulation at night, where males deposit their sperm inside the brood pouch of a female. After mating, eggs are also deposited in the brood pouch and are fertilized. Depending on the species and water temperature, females brood the eggs that take weeks to several months to hatch. Young mysids are not released until they turn into well-developed juveniles.. Mysis relicta, one of the most studied mysid shrimp found in freshwater lakes, have a 1 to 2 year life cycle depending on the productivity of the lake. Eggs of Mysis hatch into fully developed young after 3-4 months. Typical lengths are observed in each stage or instar: I â 4.5 mm, II â 9 mm, III â 12 mm, IV â 16 mm. At stage IV, individuals reach sexual maturity. Some females have a fifth instar or stage, but males do not have. Fifth instar females have 22 mm total length. (Rudstam 2009)
Mysids are generally small and transparent crustaceans, ranging from about 6 to 350 mm in length, where the length of the majority of species is less than 25 mm. They have a pair of stalked eyes and two pairs of antennae on their head fused with up to four of the thoracic segments, and covered with a well-developed carapace. One of their distinct characteristics is the number of their thoracic appendages, where they have six to eight. Their pereopods are biramous or separated into two branches. Also, they have a distinctive pair of statocyst located in their tail fan or uropods. Statocyst is a sac-like organ that helps them maintain their balance and provide a sense on how they can orient themselves in their environment. Their common name Opossum Shrimp comes from their distinct characteristic or feature, having a marsupium or brood pouch. This is where the Mysids keep their eggs until they hatch and are released after reaching an early juvenile stage of development. The marsupium is a chamber formed by lamellae or oostegites on all or some of the second to eighth pairs of thoracic legs. (Lenihan 2017)
Photo from âMysid (Americamysis bahia) Survival, Growth, and Fecundity Toxicity Testsâ (EPA 2009)
Mysids are present in almost all types of aquatic environment and are filter feeders and generally classified as omnivores, feeding on algae, detritus and zooplankton. They are very important in maintaining the balance of the aquatic ecosystem. Many fish and several species rely primarily on Mysids as their food. Mysids are rich in essential fatty acids that help in the survival of fishes. In cold regions, Mysids are a source of Polyunsaturated fatty acids that are important for fishes to have over-winter survival. Their abundance can form large shoals making them an important diet of several fish. Species like the Mysis relicta were introduced in the Kootenay lake in Canada, and it increased the growth rate and population of kokanee salmon. (Rudstam, 2009)
Sensitivity with a purpose
Mysids are very sensitive to a wide variety of contaminants. They are good indicators of harmful substances in the water. They are used as test organisms in monitoring the water quality. They are great help in wastewater management and ensuring a good quality of water in the estuarine and coastal areas since this is used in several water quality tests like the Mysid (Americamysis bahia) Survival, Growth, and Fecundity Toxicity Tests. This test is used by the U.S. Environmental Protection Agency to evaluate effluents in terms of its toxicity to biota and their impact on the natural environment. (Anderson et al. 2016; EPA 2009)
Mysids are very important especially in the aquaculture industry. They are used as food for different species of fish and a good source of nutrients for fishes being cultured like trout in the lakes of North America and Europe. Some species of Mysid are utilized as ingredients for fermented fish products. Shousuru is a Japanese fish sauce produced from fish meat added to 10% mysid, where the shrimp and mysid are used to color the sauce. (Ohshima et al. 2014)Â
Mysids have cannibalistic behavior, where some eat weaker individuals. In fact, some parents may eat some of their babies!
Hemimysis anomala or bloody-red shrimp is a species of Mysid Shrimp that can form reddish swarms in the shadows of piers and boats. They can spread and multiply rapidly and are considered âhigh-risksâ for invasion of inland lakes in the US.
 Invasion!
 Tragic Honeymoon
After mating, male Mysid (Mysis relicta) dies and the female lives for several months. A little sacrifice for the next generation.
NOAA. n.d. Great Lakes New Invader: Bloody Red Shrimp (Hemimysis anomala). GLANSIS. Rretrieved from: https://www.glerl.noaa.gov/res/Programs/glansis/hemi_brochure.html#:~:text=Mysids%20are%20often%20called%20opossum,larger%20shrimps%20and%20other%20decapods.Â
Sawamoto, Shozo. 2013. Current Status of Mysid Taxonomy in Southeast Asia. Researchgate.net. Available from: https://www.researchgate.net/publication/307791935_CURRENT_STATUS_OF_MYSID_TAXONOMYIN_SOUTHEAST_ASIAÂ
Rudstam, L.G. 2009. Other Zooplankton. Encyclopedia of Inland Waters. Science Direct. Available from: https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/mysisÂ
Anderson B., Philips B. 2016. Saltwater Toxicity Test. Science Direct. Available from: https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/mysidaÂ
Jones, D.A. 2003. Characteristics of Crustacea. Science Direct. Available from: https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/mysidaÂ
Porter, M.L. 2016. Collecting and Processing Mysids, Stygiomysids, and Lophogastrids. Journal of Crustacean Biology. Available at: https://academic.oup.com/jcb/article/36/4/592/2735746Â
Ohshima T, Giri A. 2014. FERMENTED FOODS-Traditional Fish Fermentation Technology and Recent Developments. Science Direct. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/neomysisÂ
Lenihan, Jamie. 2017. Opossum Shrimp. Vic High Marine. Available at: https://www.vichighmarine.ca/opossumshrimp/Â
EPA. 2009. Mysid (Americamysis bahia) Survival, Growth, and Fecundity Toxicity Tests. U.S. Environmental Protection Agency. Office of Wastewater Management. 1200 Pennsylvania Ave., NW Washington DC
Zooplankton of the Great Lakes. Central Michigan University. Available at: http://people.cst.cmich.edu/mcnau1as/zooplankton%20web/mysis/mysis.htmlÂ
Order Mysidacea. Key to Australian Freshwater and Terrestrial Invertebrates. https://keys.lucidcentral.org/keys/v3/TFI/start%20key/key/crustacea%20key/Media/HTML/Mysidacea.html
