Made famous by the movies “Finding Nemo” and “Finding Dory” clownfish are about 9cm in length with rounded fins. The most common type of clownfish are orange in colour with three white bands outlined in black across their bodies. These fish were given the name 'clown fish' because of their bright colours and because they always appear to be 'clowning around'. They are very active fish that often appear to be doing all sorts of acrobatics. Monay types of colwnfish live in the Great Barrier Reef off the north-eastern coast of Australia.
The clownfish, with its distinctive orange with white stripes, depicted in the movie 'Finding Nemo' was an ocellaris clownfish (Amphiprion ocellaris), also known as the false percula clownfish or common clownfish. These fish are found on the Great Barrier Reef.
Clownfish live in small groups dominated by the largest female and one or more smaller male clownfish. They are aggressive and territorial by nature and will fiercely defend their home, the sea anemone against other clownfish and predators.
Clownfish are hermaphrodites. All clownfish are born male. The dominant fish in the group, usually the largest, will always be female. The second most dominant will be a male, and her breeding partner. All other members of the group will remain male. If this dominant female dies, then the next most dominate member of the group, in this case her former partner the dominant male, will morph into a female. And the next most dominant member of the group will become her breeding partner.
Clownfish are referred to as anemonefish because they make their home only amongst sea anemones whose poisonous tentacles offer them protection from predators. It is for this reason that the clownfish is known as an 'anemone-fish'. Of the more than 1000 types of sea anemone in the ocean only 10 are used by anemonefish.
Since sea anemones prefer the shallower waters of the Great Barrier Reef where there is ample sunlight this is where clownfish are found too. A single familial group of clownfish may occupy a sea anemone and always stay in very close proximity to it.
Although the sea anemone paralyses and kills fish that touches it, it does not kill the clownfish. The clownfish it seems is immune to the sea anemone's poison. The clownfish attains this immunity because of a thick layer of mucus that covers its entire body. This mucus layer is three to four times thicker than on other similar fish and bears a very close resemblance to the sea anemone’s own mucus chemistry.
One theory is that a young clownfish builds up immunity by gently brushing against the sea anemone and being stung mildly. This causes the clownfish’s body to secrete a special soothing, protective mucus as a reaction to this. In the process it is possible that some of the sea anemone’s mucus acquired with the sting is incorporated into the clownfish’s mucus better helping it mimic the sea anemone’s own mucus chemistry. The clownfish now covered in its protective mucus amour, does not trigger the nematocyst discharge response in the sea anemone. It can then swim through the tentacles the sea anemone with ease, living in a well-armed fortress protected against predators.
The clownfish and its sea anemone host live in a mutually beneficial symbiotic relationship. The sea anemone provides the little clownfish with a home and protection, and the clownfish in turn provides the sea anemone a number of services. This relationship is called mutualism because both parties gain a benefit from their cooperation. There is no evidence to suggest that the sea anemone definitely needs the clownfish or that the clownfish needs the sea anemone for survival. They have just figured out that life is much better when they both help each other.
The small colourful clown fish attracts predators towards itself as its darts in and out of the sea anemone. The sea anemone then ensnares and consumes these predators. Scraps from the meal are ejected by the sea anemone and these in turn are eaten by the clownfish.
A clownfish may take bits of food too large for it to consume itself and feed these to the sea anemone. There are even reports that it may capture a prey and drag it into the grasping tentacles of a waiting sea anemone.
The see anemone ejects much uneaten material. The clownfish happily eats this food debris effectively cleaning house for the sea anemone but getting a free meal in exchange for its cleaning services. The clownfish also performs other maintenance services such as removing dead tentacles.
The clownfish being very territorial and aggressive will defend its home from predator, such as butterfly fish, that are likely to harm its host sea anemone.
The clownfish’s busybody darting in and out of the sea anemone's tentacles serves a useful purpose of aerating between the sea anemone’s tentacles but more importantly this constant movement also dislodges debris which may be lodged between its tentacles.
Clownfish are omnivorous, eating both animal and plant matter. Besides eating the dead tentacles of their sea anemone host and any leftovers from the sea anemone's meals, clownfish also eat plankton, mollusc, zooplankton, phytoplankton, small crustaceans and various algae.
Clownfish in the more tropical waters of the Great Barrier Reef spawn all year round and seem to be linked to the lunar cycle. At this time the male attracts the female by courting her by dancing in front of her, biting and extending his fins. The male then readies a patch of rock at the base of their host sea anemone. Spawning begins when the female swims over the patch cleaned for her by the male and deposits 100 to 1000 eggs. The male follows her and fertilises them. The female will then return to take care of the sea anemone while the male stays behind to guard the eggs until they hatch. He will remove debris and dead eggs and fan the eggs with his fins and mouth to keep them well oxygenated. The eggs will hatch in 6 to 7 days and the juvenile clownfish will remain in the vicinity for a few more days until they develop the protective mucus coating necessary for them to venture into the sea anemone.
Even through clownfish are reasonably well protected by their sea anemone host the do fall prey to large fish especially sharks and eels. One of the most insidious threats to these fish come from human who capture them to keep as pets in tanks and aquariums. Presently they are one of the most popular aquarium fishes.
The clownfish is not considered to be endangered.
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