Acartia tonsa

By Robert Muñoz

Also commonly known as Cyclops 

Acartia tonsa are translucent copepod species that can be found in most of the worlds estuaries and coastal waters. Many plankton are common to estuarine ecosystem and can live in a wide range of temperatures and salinities. Acartia tonsa can be found in estuaries and coastal waters that are warm all year-round. In colder climates like the North Atlantic it is the dominant zooplankton in both spring and summer. In the winter Acartia tonsa produce eggs in colder geographic regions. When the temperature passes 15°C (59°F) the eggs hatch.

Acartia tonsa TaxonomieAcartia tonsa in red tide

Class           Maxillopoda 
Subclass     Copepoda 
Order           Calanoida            
Family         Acartiidae 
Genus          Acartia 
Species       Acartia tonsa                        

Maxillopoda are generally small animals with barnacles being the exception to this rule. They commonly have shortened bodies, with a smaller abdomen that normally doesn’t have appendages. The most abundant and diverse groups within the Maxillopoda are Ostracods, copepods, and barnacles. Copepoda (meaning “oar-feet”) are a group of small crustaceanss found in the sea and almost in every freshwater habitat. Some species are benthic (living on the ocean floor), some are planktonic (drifting in sea waters), and some continental species may live in limnoterrestrial habitats and other wet terrestrial places. Calanoida is a kind of zooplankton that include 40 families with about 1800 species of both marine and freshwater copepods. Acartiidae is a calanoid copepods there are over 100 described species distributed throughout the world’s oceans, mainly in temperate areas. Acartia is a genus of marine calanoid copepods. They are epipelagic, estuarine, zooplanktonic found throughout the oceans of the world.

Acartia tonsa is a widely spread species: Indian Ocean, Malay Archipelago, Cayenne, Atlantic and Pacific coasts of the North and South Americas, Black, Azov and Mediterranean Seas (Kurashova, 2002). Acartia tonsa is found throughout the water column, but mainly occurs in surface layers, a water temperature of at least + 10°C is required for successful reproduction. The species does best at salinities between 15 and 22 psu, but in laboratory experiments has survived everything from 0 to 77 psu. In the Caspian Sea, however, maximum growth occurs at 7-8 psu. In other types of seas worldwide, the species is associated with a belt of subtropical, tropical and other warm waters. Its distribution could be influenced by shipping as it occurs in estuarine sites of less than 33 ‰ salinity, which are also of higher temperatures than off-shore waters and provide the temperatures required for reproduction. This species produces diapause eggs which may have helped with transport in ballast water (Eno et al. 1997).

Acartia tonsa are important in many food webs, taking in energy from phytoplankton and algae then ‘repackaging’ it for consumption by higher trophic level predators. Many commercial fish are dependent on calanoid copepods for diet in either their larval or adult forms. Baleen whales such as bowhead whales, sei whales, right whales and fin whales eat calanoid copepods. These pelagic copepods can represent 55-95% of the copepod populations in some areas. They also play an important role in the mixing and cycling of nutrients and energy in marine ecosystems, forming a trophodynamic link connecting primary (phytoplankton) and tertiary (e.g., planktivorous fish) production, and are considered a keystone species. They are also important regulators of the marine nitrogen cycle, excreting both inorganic nitrogen (as ammonium) and organic (urea). (Holste and Peck, 2005; Mauchline, 1998; Miller and Roman, 2008; Turner, et al., 1979)


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  7. Turner, J., M. Postek, S. Collard. 1979. Infestation of the Estuarine Copepod Acartia tonsa with the Ciliate Epistylis. Transactions of the American Microscopical Society, 98/1: 136-138.