''Acartia tonsa'' is a species of marine

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

in the family

Acartiidae Acartiidae is a family of calanoid copepods distinguishable by the rostral margin not being extended. They are epipelagic, plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are u ...

Distribution

''Acartia tonsa'' is a species of

calanoid Calanoida is an order of copepods, a group of arthropods commonly found as zooplankton. The order includes around 46 families with about 1800 species of both marine and freshwater copepods between them. Description Calanoids can be distinguis ...

copepod that can be found in a large portion of the world's

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

and areas of

upwelling Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted surface water. The nutr ...

where food concentrations are high. Like many

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

common to estuarine

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

s, they can live in a wide range of temperatures and

salinities Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

. The wide distribution of ''Acartia tonsa'' may be a result of these copepods being transported as ballast in ships. Their tolerance to changes in salinity has likely contributed to their success as an invasive species in some regions.

Characteristics

''Acartia tonsa'' is translucent, and is usually between about in length in females, and from about in males. It " n be differentiated from closely related species by their long first antennae (at least half the length of their bodies) and biramous (branched) second antennae, as well as the presence of a joint between their fifth and sixth body segments".

Ecology and behavior

In estuaries and coastal waters which are warm throughout the year, ''A. tonsa'' is found year-round. In cooler climates including the North Atlantic, it is frequently the dominant

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

in the spring and summer. ''Acartia tonsa'' produces eggs in the winter in colder geographic regions. The eggs hatch when temperatures exceed . They are an important food source for many commercial fish species. Several studies indicate they aggregate near the ocean floor during the day and rise closer to the surface at night. This behavior likely helps ''A. tonsa'' avoid predators who rely on vision to locate and capture prey.

Feeding

''A. tonsa''

nauplii Nauplius, Nauplia or Nauplios , may refer to : Greece-related * Nauplius (mythology), in Greek mythology, the son of Poseidon and Amymone, the father of Palamedes, and also the name of an Argonaut * Nauplia Nafplio ( ell, Ναύπλιο) is a ...

and adults feed on phytoplankton as well as planktonic

ciliate The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a ...

s and

rotifer The rotifers (, from the Latin , "wheel", and , "bearing"), commonly called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic pseudocoelomate animals. They were first described by Rev. John H ...

s. It acts as a

suspension feeder Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

when feeding on phytoplankton. When feeding on motile prey it acts as an ambush feeder; it stays nearly motionless in the water, detects movement of its prey, and then jumps toward the prey. Moderate amounts of turbulence improve rates of ambush feedings.

References

External links

* {{Taxonbar, from=Q6550901 Calanoida Crustaceans described in 1849 Cosmopolitan arthropods Taxa named by James Dwight Dana