Sunday, 13 February 2011

Manta Ray

Image via Wikipedia
Oh wow! Look, there's a Manta Ray! Manta rays are exceptionally elegant and extremely large oceanic fish. They don't so much swim as glide gracefully through the sea looking all beautiful and wonderful and lovely. They're also known as Devilfish, which certainly seems like a reasonable description for a humongous fish with huge wings and a massively gaping mouth between two cephalic lobes. Especially if you didn't realise that they are basically harmless so long as you don't stand in their way and ask them to go around. Mantas are related to sharks, and like sharks they have a skeleton made of cartilage and lack a swim bladder, achieving buoyancy with a great, big, oily liver instead.

Image via Wikipedia
Mantas usually reach about 6.7 metres (22 feet) across from tip of gigantic pectoral fin to tip of gigantic pectoral fin, with a weight of 2,300 kilograms (5,100 lb). This makes them the biggest of all rays. They can be found all around the world, sticking close to the warmth of the equator, the light of surface waters and, usually, the abundant food of coral reefs.

While mantas have a similarly flattened body as other skates and rays (batoids), they enjoy a completely different lifestyle. Most batoids (isn't that a wonderfully descriptive name? Better than deviloid anyway.) spend their lives at the bottom of the sea, seeking out molluscs and crustaceans to crush and eat. Mantas on the other hand, live the high life, soaring over their kin (looking all refined and dignified and sophisticated). The tough teeth that once would have crunched through shells and exoskeletons are reduced to tiny pin heads on the lower jaw and are absent entirely on the upper. Instead, mantas swim around (gracefully) with their mouth agape to a preposterous and rather revealing degree (not so graceful). Tiny plankton gets caught up in the gills and provides this giant with all the food it needs. It seems like those devilish lobes at the head are used to funnel and sweep plankton toward the mouth.


Image via Wikipedia
Mantas also have a thicker coating of mucus than do most other bottom-feeding skates and rays. Yuck! It probably protects them in their lofty heights, but still, yuck! Indeed, genteel and urbane and estimable they may be, but mantas are still capable of boisterous behaviour. They can occasionally be seen leaping out of the water, attaining heights of some 3 metres before making splash-down. How high do these guys want to get!? The splash is so loud that some believe it's some kind of communication, perhaps to potential mates. It could also help in dislodging parasites, which I guess is a risk when you swim around with your mouth wide open in search of tiny little creepy crawlies. Mantas are frequent visitors of cleaner fish who swim around the skin and right into the mouth and gill slits in search of dead skin and parasites to eat.

Image via Wikipedia
There is another difference between mantas and other rays. First I should say that recent studies suggest there are 2 different species of manta ray. One is slightly smaller and stays near reefs, the other is larger and retains a vestigial sting of a stingray. It's tiny and useless like their teeth, but it's there, while the reef manta has none at all. The bigger mantas also undertake a vast 700 mile (1,100km) journey from Mozambique, near Madagascar, to the Maldives, south of India. This is the longest journey undertaken in the Indian Ocean and it appears to have something to do with breeding. Females give birth to just one pup after a 1 year gestation. That youngster can be 1.2 metres (4 feet) across at birth, so you can see where all that time goes!

Before 2 species it was thought that there was just one. Before that, it was thought there were several. That gigantic journey half way across the Indian Ocean is a recent discovery. It's remarkable how many secrets such a massive and charismatic and renowned animal has managed to keep.

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