BUTTERFLYFISH

The Chaetodontidae family - butterflyfish - is a large group of around
120 species and 10 genera. The exact number varies,depending
on what classification scheme you look at, but it comes down
to one thing - there’s rather a lot of these guys. They are fairly
small, generally up to 22 centimetres in length, however, the lined butterflyfish grows to 30 cm.

Their shape is always a deep-bodied disc, and thin from side to side, with a single dorsal fin. The family name derives from the Greek words for hair and tooth as they have rows of brush-like teeth found in their tiny protruding mouths. Many butterflies are confused with angelfish, and there are similarities, but angels can be spotted by noting the sharp spine that sits across the lower edge of their gills.

Most butterflyfish live in tropical seas in fairly shallow water and on coral reefs although some choose temperate or subtropical and head down to deeper water. The deepest species is found at 200 metres. It's thought that theseoutsiders settled around rocky reefs after drifting in open ocean long enough to remove them from their original breeding ground.

Having said that, once adult, most butterflyfish do stick to a particular home range. Coral eaters stay on coral reefs, forming a mating pair. They’ll even stake a claim to their own head of coral. Many live as heterosexual couples that swim in tandem around their private patch of reef. Just to be contrary, a couple of types form large groups that hang around together in swarms. At dusk they find shelter in a reef recess and become inactive. As they settle in for the night, daytime colours pale and markings change.

Like real butterflies, the fishy versions display impressive body decoration. Masks and false eyespots are a great costume, along with a variety of stripes, bands and checks in a myriad of colours. All this is used for both defensive and social reasons. Slight variations in patterns help members of a species to recognise a buddy and let potential predators know that they are bony and not really worth the trouble to eat. Confusing colours and patterns can also deflect a predator away. The four spot butterfly has what looks like four eyes which makes it much harder for predators to work out which end is the vulnerable head and which the tail.  Eye-bands also help camouflage the location of their eyes which makes it harder for potential predators to guess the direction the little chap will dart when attacked.

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