Mysis diluviana is a mysid crustacean

Crustacean

Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

 (opossum shrimp) that inhabits freshwater lakes of northern North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

.

Appearance

Mysis is a small, transparent shrimp

Shrimp

Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...

-like crustacean, of less than 25 millimetre (0.984251968503937 in) length. It has two pairs of relatively long antenna

Antenna (biology)

Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....

e, associated with rounded antennal plates; large, stalked compound eyes; the thorax

Thorax

The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...

 covered by a coat-like carapace

Carapace

A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...

; a muscular, cylindrical abdomen

Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...

; and a tail fan featuring a telson

Telson

The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...

 with a V-shaped terminal cleft.

Reproducing females bear a prominent brood pouch (marsupium) between their thoracal legs. The pleopods (abdominal legs) of Mysis are reduced, except for a specialized pair of mating legs in males.

Distribution and related species

The natural distribution of Mysis diluviana comprises the Great Lakes

Great Lakes

The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...

 of North America, and many other coldwater lakes across Canada and in northern parts of the United States, including Wisconsin

Wisconsin

Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...

 (e.g. Green Lake, Trout Lake

Trout Lake (Wisconsin)

Trout Lake is one of the largest lakes in Vilas County, Wisconsin. It is located near the town of Boulder Junction, Wisconsin. It is known in the area for having good fishing, and a relatively large amount of undeveloped shoreline. Trout Lake is one of the few inland lakes in Wisconsin to host lake...

, and Geneva Lake

Geneva Lake

Geneva Lake is a body of freshwater in southeastern Wisconsin in Walworth county. On its shores are the city of Lake Geneva, and the villages of Fontana-on-Geneva-Lake, and Williams Bay....

) and northern New York State

New York

New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

 (e.g. Finger Lakes

Finger Lakes

The Finger Lakes are a pattern of lakes in the west-central section of Upstate New York in the United States. They are a popular tourist destination. The lakes are long and thin , each oriented roughly on a north-south axis. The two longest, Cayuga Lake and Seneca Lake, are among the deepest in...

, Lake Champlain

Lake Champlain

Lake Champlain is a natural, freshwater lake in North America, located mainly within the borders of the United States but partially situated across the Canada—United States border in the Canadian province of Quebec.The New York portion of the Champlain Valley includes the eastern portions of...

). As it inhabits the areas covered by ice sheet

Ice sheet

An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...

s during the last glacial period, the species has been called a glacial relict

Relict

A relict is a surviving remnant of a natural phenomenon.* In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas....

.

Mysis diluviana has also been transferred to lakes outside its native range, to provide a new fish-food object, e.g. to Lake Tahoe

Lake Tahoe

Lake Tahoe is a large freshwater lake in the Sierra Nevada of the United States. At a surface elevation of , it is located along the border between California and Nevada, west of Carson City. Lake Tahoe is the largest alpine lake in North America. Its depth is , making it the USA's second-deepest...

 (Nevada

Nevada

Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...

, California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

) and Kootenay Lake

Kootenay Lake

Kootenay Lake is a lake located in British Columbia, Canada and is part of theKootenay River. The lake has been raised by the Corra Linn Dam and has a dike system at the southern end, which, along with industry in the 1950s-70s, has changed the ecosystem in and around the water...

 (British Columbia

British Columbia

British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...

).

Mysis diluviana is the only mysid species native in the Great Lakes and adjacent waterbodies. Recently however another, invasive mysid of European origin, Hemimysis anomala

Hemimysis anomala

The bloody-red mysid, Hemimysis anomala, is a shrimp-like crustacean in the Mysida order, native to the Ponto-Caspian region, which has been spreading across Europe since the 1950s. In 2006, it was discovered to have invaded the North American Great Lakes.-Distribution:The species is native to...

, has rapidly spread in the Great Lakes. The two species live in different habitat

Habitat

* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...

s.

The native mysids in freshwater lakes of the Canadian Arctic and in coastal lagoons of Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

 belong to another, closely related species Mysis segerstralei. Both M. diluviana and M. segerstralei were previously called Mysis relicta

Mysis relicta

Mysis relicta is a shrimp-like crustacean in the Mysida order, native to lakes of Northern Europe and to the brackish Baltic Sea.-Appearance:Mysis is a small, transparent shrimp-like crustacean, of less than 2.5 cm length...

, which was until recently considered a circumpolar taxon. After revision in 2005, Mysis relicta is considered a purely European species.

Ecology

Mysis diluviana is found in deep, cold oligotrophic lakes with high levels of dissolved oxygen, where is stays mainly below the thermocline

Thermocline

A thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below...

.

Mysis is an opportunistic feeder with both predatorial and filter feeding habits. When zooplankton

Zooplankton

Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...

 are abundant, they serve as the primary food source; when scarce, it will feed on phytoplankton

Phytoplankton

Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...

, suspended organic detritus

Detritus

Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...

 or from the surface of benthic organic deposits.