Hemimysis anomala
Encyclopedia
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
.
, the Azov Sea and the eastern Caspian Sea
. It has historically occurred in the lower reaches of the Don
, Danube
, Dnieper and Dniester
rivers. In Europe, it has recently spread north west, reaching the Baltic Sea
in 1992 and the United Kingdom
in 2004. The mysid's spread has been facilitated via its deliberate introduction into reservoirs on the Volga and Dnieper rivers in the 1950s and 1960s to serve as fish food. Despite its spread throughout Europe, it is considered to be endangered in some parts of its indigenous range (Ukraine
).
The species has entered the Great Lakes via the ballast water exchange; it was reported for the first time in 2006 from two disjunct regions: southeastern Lake Ontario
at Nine Mile Point near Oswego, New York
in May 2006, and from a channel connecting Muskegon Lake
to Lake Michigan
in November 2006. Specimens resembling H. anomala have also been found in the stomach contents of a white perch
collected near Port Dover, Lake Erie
in August 2006. The species was discovered in the Saint Lawrence River
in July 2008; it is now found in all the major Great Lakes waterbodies, except for Lake Superior
.
and telson
. The intensity of colouration, believed to be associated with the species' crepuscular
behaviour, varies with contraction or expansion of the chromatophores in response to light and temperature conditions; in shaded areas, individuals tend to have a deeper red colour. Juveniles are more translucent than adults. Preserved individuals lose their colour, becoming opaque. H. anomala is distinguishable from other mysid species including the Great Lakes' native opossum shrimp Mysis diluviana
by its truncated telson with a long spine at both corners; by contrast, M. diluviana has a forked telson.
that feeds primarily on zooplankton
, particularly cladocerans, but also consumes detritus
, phytoplankton
(particularly green algae
and diatom
s), and insect larvae, and is occasionally cannibalistic
. Younger individuals feed mainly on phytoplankton. The proportion of zooplankton consumed in the mysid's diet increases with its body size. A bloody-red mysid feeds using its thoracic limbs, either by capturing prey with its endopods or by removing food particles from its body that are filtered from incoming currents by its exopods.
s to the upper water column at twilight, then return to the profundal zone at dawn. Only males tend to undergo these migrations. Juvenile H. anomala often inhabit different positions (usually higher) in the water column than adults, possibly to avoid cannibalism. Being more transparent, juveniles may be less at risk of fish predation than adults. The adults are fast swimmers, moving at several centimetres per second when alarmed. Bloody-red mysids generally avoid areas where other mysid species are found. Their tendency to aggregate creates locally dense swarms up to several square meters in area. During daylight hours, especially in late summer, these reddish swarms can be observed in the shadows of piers, boats, or breakwalls; at night, the swarms disperse. The species is also reported to spend daylight hours hiding in rocky crevices and boulder cavities.
s per year. Brood size is correlated with female length and ranges from 6 to 70 embryos per individual.
, while H. anomala is best adapted to warmer conditions. In Europe, the species has been observed to disrupt food web
s and alter nutrient and contaminant cycles of environments into which it was introduced. The mysid has been associated with reduction of zooplankton biomass and biodiversity, while having an opposite effect on phytoplankton. Pelagic fish in many ecosystems have been negatively affected by the species' introduction; however, salmonids and benthic fish seem to benefit from the new food source. The species' routine vertical migration through the water column results in continuous cycling of pollutants, such as heavy metals
, that would otherwise be confined to the benthic zone.
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 the Ponto-Caspian region, which has been spreading across 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...
since the 1950s. In 2006, it was discovered to have invaded
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
the North American
North American
North American generally refers to an entity, people, group, or attribute of North America, especially of the United States and Canada together.-Culture:*North American English, a collective term used to describe American English and Canadian English...
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...
.
Distribution
The species is native to freshwater margins of the Black SeaBlack Sea
The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...
, the Azov Sea and the eastern Caspian Sea
Caspian Sea
The Caspian Sea is the largest enclosed body of water on Earth by area, variously classed as the world's largest lake or a full-fledged sea. The sea has a surface area of and a volume of...
. It has historically occurred in the lower reaches of the Don
Don River (Russia)
The Don River is one of the major rivers of Russia. It rises in the town of Novomoskovsk 60 kilometres southeast from Tula, southeast of Moscow, and flows for a distance of about 1,950 kilometres to the Sea of Azov....
, Danube
Danube
The Danube is a river in the Central Europe and the Europe's second longest river after the Volga. It is classified as an international waterway....
, Dnieper and Dniester
Dniester
The Dniester is a river in Eastern Europe. It runs through Ukraine and Moldova and separates most of Moldova's territory from the breakaway de facto state of Transnistria.-Names:...
rivers. In Europe, it has recently spread north west, reaching the 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...
in 1992 and the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
in 2004. The mysid's spread has been facilitated via its deliberate introduction into reservoirs on the Volga and Dnieper rivers in the 1950s and 1960s to serve as fish food. Despite its spread throughout Europe, it is considered to be endangered in some parts of its indigenous range (Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
).
The species has entered the Great Lakes via the ballast water exchange; it was reported for the first time in 2006 from two disjunct regions: southeastern Lake Ontario
Lake Ontario
Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north and southwest by the Canadian province of Ontario, and on the south by the American state of New York. Ontario, Canada's most populous province, was named for the lake. In the Wyandot language, ontarío means...
at Nine Mile Point near Oswego, New York
Oswego, New York
Oswego is a city in Oswego County, New York, United States. The population was 18,142 at the 2010 census. Oswego is located on Lake Ontario in north-central New York and promotes itself as "The Port City of Central New York"...
in May 2006, and from a channel connecting Muskegon Lake
Muskegon Lake
Muskegon Lake is a fresh-water lake in Muskegon County, Michigan, USA. Located in the lower peninsula at the mouth of the Muskegon River, Muskegon Lake forms a broad harbor along the eastern shoreline of Lake Michigan, approximately wide by long....
to Lake Michigan
Lake Michigan
Lake Michigan is one of the five Great Lakes of North America and the only one located entirely within the United States. It is the second largest of the Great Lakes by volume and the third largest by surface area, after Lake Superior and Lake Huron...
in November 2006. Specimens resembling H. anomala have also been found in the stomach contents of a white perch
White perch
The white perch, Morone americana, is not a true perch but is, rather, a fish of the temperate bass family, Moronidae, notable as a food and game fish in eastern North America.The name "white perch" is sometimes erroneously applied to the white crappie....
collected near Port Dover, Lake Erie
Lake Erie
Lake Erie is the fourth largest lake of the five Great Lakes in North America, and the tenth largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also has the shortest average water residence time. It is bounded on the north by the...
in August 2006. The species was discovered in the Saint Lawrence River
Saint Lawrence River
The Saint Lawrence is a large river flowing approximately from southwest to northeast in the middle latitudes of North America, connecting the Great Lakes with the Atlantic Ocean. It is the primary drainage conveyor of the Great Lakes Basin...
in July 2008; it is now found in all the major Great Lakes waterbodies, except for Lake Superior
Lake Superior
Lake Superior is the largest of the five traditionally-demarcated Great Lakes of North America. It is bounded to the north by the Canadian province of Ontario and the U.S. state of Minnesota, and to the south by the U.S. states of Wisconsin and Michigan. It is the largest freshwater lake in the...
.
Anatomy and morphology
Mature individuals reach 6–13 mm (0.236220472440945–0.511811023622047 ) in length; females are slightly larger than males. The species can be ivory-yellow in colour or translucent, but exhibits pigmented red chromatophores in the carapaceCarapace
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...
and 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...
. The intensity of colouration, believed to be associated with the species' crepuscular
Crepuscular
Crepuscular animals are those that are active primarily during twilight, that is during dawn and dusk. The word is derived from the Latin word crepusculum, meaning "twilight." Crepuscular is, thus, in contrast with diurnal and nocturnal behavior. Crepuscular animals may also be active on a bright...
behaviour, varies with contraction or expansion of the chromatophores in response to light and temperature conditions; in shaded areas, individuals tend to have a deeper red colour. Juveniles are more translucent than adults. Preserved individuals lose their colour, becoming opaque. H. anomala is distinguishable from other mysid species including the Great Lakes' native opossum shrimp 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...
by its truncated telson with a long spine at both corners; by contrast, M. diluviana has a forked telson.
Habitat
The bloody-red mysid favours hard bottom surfaces, including rocks and shells and avoids soft bottoms and areas of dense vegetation or high siltation. In its native range, the species is found in water depths ranging from 0.5 to 50 m (1.6 to 164 ft), although they generally inhabit depths of 6 metre. The species is normally found in lentic waters, although it has successfully established in European rivers; it has also been found along rocky, wave-exposed shorelines. It tolerates salinity concentrations of 0–19 ppt and prefers water temperatures of 9–20 °C (48.2–68 F). Populations may survive temperatures of 0 °C (32 °F) over winter, but not without substantial mortality.Food
H. anomala is an opportunistic omnivoreOmnivore
Omnivores are species that eat both plants and animals as their primary food source...
that feeds primarily on 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"...
, particularly cladocerans, but also consumes 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...
, 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...
(particularly green algae
Green algae
The green algae are the large group of algae from which the embryophytes emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic...
and diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
s), and insect larvae, and is occasionally cannibalistic
Cannibalism (zoology)
In zoology, cannibalism is the act of one individual of a species consuming all or part of another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded for more than 1500 species...
. Younger individuals feed mainly on phytoplankton. The proportion of zooplankton consumed in the mysid's diet increases with its body size. A bloody-red mysid feeds using its thoracic limbs, either by capturing prey with its endopods or by removing food particles from its body that are filtered from incoming currents by its exopods.
Behaviour
Individuals remain near profundal sediments during the day, migrate in swarmSwarm
Swarm behaviour, or swarming, is a collective behaviour exhibited by animals of similar size which aggregate together, perhaps milling about the same spot or perhaps moving en masse or migrating in some direction. As a term, swarming is applied particularly to insects, but can also be applied to...
s to the upper water column at twilight, then return to the profundal zone at dawn. Only males tend to undergo these migrations. Juvenile H. anomala often inhabit different positions (usually higher) in the water column than adults, possibly to avoid cannibalism. Being more transparent, juveniles may be less at risk of fish predation than adults. The adults are fast swimmers, moving at several centimetres per second when alarmed. Bloody-red mysids generally avoid areas where other mysid species are found. Their tendency to aggregate creates locally dense swarms up to several square meters in area. During daylight hours, especially in late summer, these reddish swarms can be observed in the shadows of piers, boats, or breakwalls; at night, the swarms disperse. The species is also reported to spend daylight hours hiding in rocky crevices and boulder cavities.
Life history
H. anomala breeds from April to September / October. Sexual maturity occurs in 45 days; life span is about 9 months. Females become ovigerous at 8–9 °C (46.4–48.2 F) and produce 2 to 4 broodOffspring
In biology, offspring is the product of reproduction, of a new organism produced by one or more parents.Collective offspring may be known as a brood or progeny in a more general way...
s per year. Brood size is correlated with female length and ranges from 6 to 70 embryos per individual.
Impact as an invasive species
Given the species' very recent introduction into the Great Lakes, its impact is yet to be established. It is not expected to compete with the native M. relicta, as it prefers the cold water environments below the lakes' 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...
, while H. anomala is best adapted to warmer conditions. In Europe, the species has been observed to disrupt food web
Food web
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
s and alter nutrient and contaminant cycles of environments into which it was introduced. The mysid has been associated with reduction of zooplankton biomass and biodiversity, while having an opposite effect on phytoplankton. Pelagic fish in many ecosystems have been negatively affected by the species' introduction; however, salmonids and benthic fish seem to benefit from the new food source. The species' routine vertical migration through the water column results in continuous cycling of pollutants, such as heavy metals
Heavy metals
A heavy metal is a member of a loosely-defined subset of elements that exhibit metallic properties. It mainly includes the transition metals, some metalloids, lanthanides, and actinides. Many different definitions have been proposed—some based on density, some on atomic number or atomic weight,...
, that would otherwise be confined to the benthic zone.