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Clownfish
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Clownfish and anemonefish are fish from the subfamily Amphiprioninae in the family Pomacentridae. About twenty eight species are recognized, one in the genus Premnas, while the remaining are in the genus Amphiprion. In the wild they all form symbiotic relationships with sea anemones. Depending on exact species, clownfish are overall yellow, orange, reddish, or blackish, and many show white bars or patches.
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Encyclopedia
Clownfish and anemonefish are fish from the subfamily Amphiprioninae in the family Pomacentridae. About twenty eight species are recognized, one in the genus Premnas, while the remaining are in the genus Amphiprion. In the wild they all form symbiotic relationships with sea anemones. Depending on exact species, clownfish are overall yellow, orange, reddish, or blackish, and many show white bars or patches. The largest species reach a length of 18 cm (7 in), while the smallest barely reach 10 cm (4 in).
Ecology and life history
Clownfish are native to wide ranges of the warm waters of the Indian and Pacific oceans, including the Great Barrier Reef and the Red Sea. While most species have restricted distributions, others are widespread. They are generally highly host specific, and especially the genera Heteractis and Stichodactyla, and the species Entacmaea quadricolor are frequent partners. The clownfish feeds on undigested matter which otherwise potentially could harm the sea anemone, and the faecal matter from the clownfish provides nutrients to the sea anemone. It has also been suggested that the activity of the clownfish results in greater water circulation around the sea anemone. In addition to providing food for the clownfish, the sea anemone also provides safety due to its poison.
Clownfish and certain [damselfish] are the only species of fishes that can avoid the potent poison of a sea anemone. There are several theories about how this is accomplished:
- The mucus coating of the fish may be based on sugars rather than proteins. This would mean that anemones fail to recognize the fish as a potential food source and do not fire their nematocysts, or sting organelles.
- The coevolution of certain species of clownfish with specific anemone host species and may have acquired an immunity to the nematocysts and toxins of their host anemone. Experimentation has shown that Amphiprion percula may develop resistance to the toxin from Heteractis magnifica, but it is not totally protected, since it was shown experimentally to die when its skin, devoid of mucus, was exposed to the nematocysts of its host.
Clownfish live in small groups inhabiting a single anemone. The group consist of a breeding pair, which cohabit with a few non-reproductive, "pre-pubescent", and smaller male clownfish. When the female dies, the dominant male changes sex and becomes the female. This life history strategy is known as sequential hermaphroditism. Because clownfish are all born as males, they are protandrous hermaphrodites (pro=first; androus=male).This is in contrast with another form of hermaphroditism, known as protogyny, in which all fish are born as females but can change to males later.
Clownfish lay eggs on any flat surface close to their host anemones. In the wild, clownfish spawn around the time of the full moon and the male parent guards them until they hatch about 6 to 10 days later, typically 2 hours after dusk. Clownfish are omnivorous: in the wild they eat live food such as algae, plankton, molluscs, and crustacea; in captivity they can survive on live food, fish flakes, and fish pellets. They feed mostly on copepods and mysids, and undigested food from their host anemones.
Depending on the species, clownfish can lay hundreds or thousands of eggs. Clownfish were the first type of marine ornamental fish to be successfully bred in captivity on a large scale. It is one of a handful of marine ornamentals whose life cycle has been closed in captivity.
In the aquarium
Clownfish are a popular fishes for the reef aquarium of 10 gallons or more. Clownfish are now tank-bred to lower the number taken from the wild. Wild-caught tropical fishes are more likely to die within a week of purchase, due to catching methods like dynamite fishing and nets with "rockhoppers." Compared to wild-caught clownfish, tank-bred clownfish are more disease resistant and also less affected by stress when introduced to the aquarium.
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When a sea anemone is not available in an aquarium, they may settle in some varieties of soft corals, or large polyp stony corals. If the fish settles in a coral, it could agitate the fish's skin, and, in some cases, may kill the coral. Once an anemone or coral has been adopted, the clownfish will defend it. As there is less pressure to forage for food in an aquarium, it is common for clownfish to remain within 2-4 inches of their host for an entire lifetime.
Clownfish that are far removed from their parents through captive breeding may not have the same instinctual behavior to live in an anemone. They may have to be coaxed into finding the anemone by the home aquarist. Even then, there is no guarantee that the anemone will host the clownfish.
Species
- Genus Amphiprion:
- Genus Premnas:
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