Wednesday 10 November 2010

African Butterflyfish

Image: Toniher
Also known as the Freshwater Butterflyfish. Thus, we are immediately told that they are an African freshwater fish. They aren't however, related to marine butterflyfish, those ridiculously colourful tropical inhabitants of coral reefs. No, these butterflyfish have a gothic beauty all of their own.

Their dark colours would leave them drab were it not for the flowing veil of most of their fins, and the unique, rather dangerous looking spikiness of the pelvic fins as they splay out in rigid tendrils of morbid pink colour and dark stripes. I can't help but think of some recently used medieval torture device when I see those particular fins. That might just be me, though.

African Butterflyfish are found in lakes and slow moving rivers near the centre of Africa, like the Congo basin, Lake Chad, Niger and Cameroon. They are a specialised surface dwelling predator, constantly looking skyward, its upward facing jaws ready to grapple with the insects and fish that become dinner.

They have sensors on their skin which can sense the tiny waves emitted by an insect at the surface as it struggles or moves around. They can tell both the distance and the direction of the source and waste no time in getting there.

African butterflyfish actually have three jaws, one lower and two upper. This means one jaw can grip onto prey, while the other goes about the whole crushing and mashing and eating stuff.

They can even breathe air if need be and, if they can gather enough speed, they can break the surface and glide through the air a short distance and away from predators. It has large pectoral fins at its sides which are wriggled around as they go, while those tough, spiky pelvic fins act as stabilisers. It is this that gives them their name.

Reaching around 13 centimetres in length, the African butterflyfish makes for a popular aquarium fish, so long as you have a strong lid!

This little fish holds a secret though. They are the only species in their family, but the groups in Cameroon and Niger are separated by miles and don't meet up. This isn't an unheard of situation and one would usually expect them to remain genetically similar, with just a 2 or 3% difference between the lot of them. They still look the same after all. Instead, it has been discovered that they differ by as much as 15%! This is the kind of difference we would expect to see within an entire family of fishes. Characidae is a fish family, it includes piranhas and all the tiny little tetras that can be found in aquariums all over the world. That's the difference 15% can make. Just not in the case of African butterflyfish.

It has been estimated that the two groups became divided some 57 million years ago and yet, through all this time, they have scarcely changed. You can therefore consider them living fossils. Scientists are now trying to find out more about their behaviour to see if there are any big differences on that front and if they are now actually two separate species. That would be nice, another African butterflyfish! Even if they would pretty much be twins.

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