Aquatic animal

Longfin sculpin (Jordania zonope)

An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life.^[1] It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that live in them can be categorized as aquatic (water) or terrestrial (land).

The term aquatic can in theory be applied to animals that live in either fresh water (fresh water animals) or salt water (marine animals). However, the adjective marine is most commonly used for animals that live in saltwater, i.e. in oceans, seas, etc.

Aquatic animals (especially freshwater animals) are often of special concern to conservationists because of the fragility of their environments. Aquatic animals are subject to pressure from overfishing, destructive fishing, marine pollution and climate change.

Air breathing aquatic animals

In addition to water breathing animals, e.g., fishes, mollusks etc., the term "aquatic animal" can be applied to air-breathing aquatic or sea mammals such as those in the orders Cetacea (whales) and Sirenia (sea cows), which cannot survive on land, as well as to the pinnipeds (true seals, eared seals, and the walrus). The term "aquatic mammal" is also applied to four-footed mammals like the river otter (Lontra canadensis) and beavers (family Castoridae), although these are technically amphibious.

Amphibians, like frogs (the order Anura), while requiring water, are separated into their own environmental classification. The majority of amphibians (class Amphibia) have an aquatic larval stage, like a tadpole, but then live as terrestrial adults, and may return to the water to mate.

Certain fish also evolved to breathe air to survive oxygen-deprived water, such as arapaima (family Osteoglossidae) and walking catfish.

See also

• Aquatic mammal
• Aquatic plant
• Freshwater snail
• List of semiaquatic tetrapods
• Marine biology
• Marine invertebrates
• Marine mammal

References

External links

• "Annelids." Nonindigenous Aquatic Species. Web. 2 May 2012. <http://nas.er.usgs.gov/taxgroup/Annelids/>.
• National Invasive Species Information Center. Web. 2 May 2012. <http://www.invasivespeciesinfo.gov/aquatics/main.shtml>.

Aquatic ecosystem topics
Aquatic ecosystems – general and freshwater components General Acoustic ecology Adaptation Agent-based models Algal bloom Anoxic waters Aquatic animals (Insects Mammals) Aquatic plants Aquatic science Benthos Biodiversity research Bioluminescence Biomass Biomonitoring Cascade effect Colored dissolved organic matter Camouflage and mimicry Dead zone Ecohydrology Ecosystems Eutrophication Fisheries science Food chain Food web GIS and aquatic science Hydrobiology Hypoxia Isotope analysis Microbial ecology Microbial food web Microbial loop Nekton Neuston Particle Pelagic zone Photic zone Phytoplankton Plankton Pleuston Predation Productivity Ramsar Convention Respiration Schooling Sediment trap Siltation Spawning Substrate Thermal pollution Toxicology Trophic level Water column Zooplankton More... Freshwater Biology Biomes Ecosystems freshwater lake river Fish Hyporheic zone Limnology Lake stratification Macrophyte Pond Fish pond Rheotaxis Stream bed Stream pool Trophic state index Upland and lowland Water garden Wetland brackish marsh freshwater marsh swamp bog fen Environmental quality More... Ecoregions Freshwater (List) Marine (List) The Everglades Maharashtra The North Pacific Subtropical Gyre The San Francisco Estuary
Aquatic ecosystems – marine components Marine Marine biology Marine chemistry Deep scattering layer Diel vertical migration Ecosystems large marine marine) f-ratio Iron fertilization Marine snow Ocean nourishment Oceanic physical-biological process Ocean turbidity Photophore Thorson's rule Upwelling Whale fall More... Marine life Bacteriophages Census Fish coastal coral reef deep sea demersal pelagic Deep sea communities Deep sea creature Deep-water coral Invertebrates Larvae Mammals Marine life Microorganisms Paradox of the plankton Reptiles Seabirds Seashore wildlife Vertebrates Wild fisheries Marine habitats Bay mud Black smokers Coastal biogeomorphology Cold seeps Coral reefs Davidson Seamount Estuaries Intertidal ecology Intertidal wetlands Kelp forests Hydrothermal vents Lagoons Mangroves Marine biomes Marine habitats Mudflats Rocky shores Salt marshes Salt pannes and pools Seagrass meadows Sponge reefs Tide pools Issues Ecological values of mangroves Fisheries and climate change HERMIONE Marine conservation Marine conservation activism Marine pollution Marine Protected Area