Amphiprion ocellaris - Ocellaris clownfish

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The Ocellaris Clownfish, Common Clownfish or False Percula Clownfish (Amphiprion ocellaris) is a popular aquarium fish, even more so after it rose to stardom in Finding Nemo. It is very closely related to A. percula, the Orange Clownfish or "True Percula Clownfish", and often lives in association with the sea anemone Heteractis magnifica, using them for shelter and protection. Generally, Ocellaris clownfish are hardier, and slightly less aggressive than its Percula counterpart. Both species are found in coral reefs of the Indo-Pacific, particularly in the Fiji and Tonga regions.

Description

This clown anemonefish can be recognised by its orange colour with three white bars and black markings on the fins. It grows to about eight centimeters (three inches) in length. One can differentiate between Percula (true) and Ocellaris (false) by their respective colors and patterns. Ocellaris are usually less vibrantly colored, and have 11 dorsal fin-spines instead of 10, as on the Percula. Also the species have different eye arrangements, Percula have bright orange irises, making their eyes appear smaller whereas Ocellaris have grey/orange irises which make the species eyes appear bigger. There is a rare melanistic variety hailing from the reefs around Darwin, Australia, that is a dark black colour with the normal white stripes. Although not common in the wild, they are becoming more and more popular in the aquarium hobby. This species feeds on remnants that its home, the sea anemone, does not eat and nibbles on the tentecles of the anemone.

Phylogeny

The species Amphiprion Ocellaris are related to the class Osteichthyes which contains bony fish and ray-finned fish. A. Ocellaris is the most basal species in the genus Amphiprion which is closely related to the genera Premnas. The species most closely related ancestor is Amphiprion Percula, the Orange Clownfish. It is thought that A. Ocellaris specialized after diverging from the Premnas genera, scientific evidence confirms that all clownfish belonging to the genus Amphiprion could withstand the stings of only one type of anemone, after further diverging the 28 different species of clownfish including A. Ocellaris specialized to be able to resist the poisonous stings of many different species of anemone.

Analogous Structures

Clownfish have many structures which are analogous with other species, the distinctive stripes found on the clownfish can be seen in few animals. Lampropeltis triangulum elapsoidesor otherwise known as the Scarlet King Snake has a well-defined pattern of red, black and yellow bands. These two structures both have characterises that are similar in use, the bands of each species help warn off predators if the animal is in danger. These bands also help camouflage both organisms in each of their different environments. The bright orange base striped with white found on the clownfish allows it to be undetected in its surroundings of florescent corals and anemones. The red, black and yellow stripes on the Scarlet King Snake help it slither through pine woodland unnoticed.

Homologous Structures

All fish have a mucus membrane surrounding their scales. The mucus usually contains high amounts of lipids and glycoprotein’s, however the family Pomacentridae (anemone fish) have a special adaptation where the mucus coating the species is a great deal thicker. Also the protective layer lacks a specific substance that triggers nematocysts (the stings of an anemone); this allows the fish immunity against the toxic stings. Little is known about the mucus except it is genetic and passed through the generations of each species, scientists have many theories to why it is effective but none have been proven. In other families of fish, the mucus is used as protection against harmful bacteria, an osmotic regulator and also aids the fish in nest making. The difference in mucus’s has led to the divergent path of anemone fish and other species.

In Popular Culture

Nemo, an Ocellaris Clownfish is the lead character the 2003 Pixar-Disney film, Finding Nemo, and was voiced by Alexander Gould. Other Ocellaris clownfish characters that appear in the movie are Nemo's father, Marlin (voiced by Albert Brooks) and Nemo's mother, Coral (voiced by Elizabeth Perkins).