Mysis relicta
Encyclopedia
Mysis relicta is a shrimp
-like crustacean
in the Mysida order
, native to lakes of Northern Europe
and to the brackish Baltic Sea
.
-like crustacean, of less than 2.5 cm length. It has two pairs of relatively long antenna
e, associated with rounded antennal plates; large, stalked compound eyes; the thorax
covered by a coat-like carapace
; a muscular, cylindrical abdomen
; and a tail fan featuring a telson
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.
, Finland
, Sweden
, south-east of Norway
, and parts of Germany
, Poland
and Lithuania
.
Previously M. relicta was treated as a circumpolar taxon also present in North America and the Eurasian Arctic. A revision in 2005 divided these circumpolar freshwater Mysis populations into four distinct species. Apart from the North European M. relicta, these include Mysis diluviana
in lakes of the United States
and Canada
, Mysis segerstralei in the circumpolar Arctic, and Mysis salemaai in some European lakes and the Baltic.
. M. relicta is a benthopelagic species, which in the nighttime performs vertical migration towards the surface. In the Baltic Sea, M. relicta is only found in the most diluted marginal parts of the basin, where it also stays in deeper water. In the open sea it is replaced by M. salemaai.
are abundant, they serve as the primary food source; when scarce, M. relicta will feed on phytoplankton
, suspended organic detritus
or from the surface of benthic organic deposits.
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
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...
in the Mysida order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
, native to lakes of Northern Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and to the brackish Baltic Sea
Baltic Sea
The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and...
.
Appearance
Mysis is a small, transparent shrimpShrimp
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 2.5 cm 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
The distribution of Mysis relicta is restricted to previously glaciated regions in Northern Europe, including North-West RussiaRussia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
, Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...
, Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
, south-east of Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
, and parts of Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
and Lithuania
Lithuania
Lithuania , officially the Republic of Lithuania is a country in Northern Europe, the biggest of the three Baltic states. It is situated along the southeastern shore of the Baltic Sea, whereby to the west lie Sweden and Denmark...
.
Previously M. relicta was treated as a circumpolar taxon also present in North America and the Eurasian Arctic. A revision in 2005 divided these circumpolar freshwater Mysis populations into four distinct species. Apart from the North European M. relicta, these include Mysis diluviana
Mysis diluviana
Mysis diluviana is a mysid crustacean that inhabits freshwater lakes of northern North America.-Appearance:Mysis is a small, transparent shrimp-like crustacean, of less than length...
in lakes of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, Mysis segerstralei in the circumpolar Arctic, and Mysis salemaai in some European lakes and the Baltic.
Habitat
The species is found in relatively deep, cold and often oligotrophic lakes with sufficient dissolved oxygen, where is stays mainly below the thermoclineThermocline
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...
. M. relicta is a benthopelagic species, which in the nighttime performs vertical migration towards the surface. In the Baltic Sea, M. relicta is only found in the most diluted marginal parts of the basin, where it also stays in deeper water. In the open sea it is replaced by M. salemaai.
Food
M. relicta is an opportunistic feeder with both predatorial and filter feeding habits. When zooplanktonZooplankton
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, M. relicta 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.