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All About the Manta Ray

By Edited Jul 3, 2014 5 20

Giant Rays of the Deep

The Manta Ray

The manta ray was once believed to be a monotypic species – the only species in the genus Manta. They belong to the family Myliobatidae

However this taxonomy is likely to change as some authorities are pushing for a second species to be recognised. These two are called the giant manta (Manta birostris) and the reef manta (Manta alfredi). Other common names include Atlantic manta, Pacific manta and devilfish. The word 'manta' derives from the Spanish word for blanket or cloak.

It is the largest species of rays. The largest known representative had a width in excess of 7.6 metres and a weight of 1,300 kg. It has the largest brain-to-body ratio of the sharks, skates and rays and will dive as deep as 500 metres.

Manta Ray 1

The manta ray is a most graceful swimmer and has a gentle nature. Any snorkeler or diver fortunate enough to have an encounter with one of these giants is awed by its size, often describing the sensation of a dark cloud moving overhead and taking forever to go on its way.

Habitat
The manta ray is found throughout all oceans but typically around coral reefs and over continental shelves in tropical and subtropical regions.

Description
The manta ray has a skeleton composed of cartilage rather than bone.

The body shape of the manta ray is very distinctive with its triangular ‘wings’. Paddle-like lobes or feeding flaps extend in front of the mouth. These are fleshy extensions of the pectoral fins. At the top of the flaps are the eyes. On the underside of the eyes and to each side are five gill slits.

The upper surface may range from black to greyish-blue to brown and the undersides are pale. Each ray has a unique pattern of splotches and scars which can be used for identification purposes. The lower jaw has 18 rows of teeth but these are vestigial and almost hidden by skin. The cavernous mouth scoops up planktron and krill.

The spiracles are non-functional as all water is taken in through the mouth. Spiracles are small holes behind each eye. These open to the mouth but, as stated, are non-functional in the manta ray.

The body is covered with a thick mucous, much thicker than that found on other rays. Although the whip-like tail is similar to that of a stingray, there is no stinger and thus no danger to divers.

Behaviour
Manta rays are often seen in groups and spend a lot of time near the surface. Reef mantas have a stable population of 6,000 to 7,000 around the Maldives where the water is rich in plankton. Reef mantas may form a feeding vortex with whale sharks.

Cleaning Station

Mantas commonly visit cleaning stations, making slow circuits round an area while small fish ‘clean’ the manta of parasites and dead cells. Remoras, angelfish and wrasse swim in the gills and over the body, feeding off the dead tissue. Sucker fish have a large sucking disc on top of the head and may attach themselves to larger fish, picking up dropped prey .

Mantas will sometimes launch themselves from the ocean, hitting the water with a slap as they land again. This may be a way of communicating with others or just a play activity. Although they seem graceful and slow, they can move at fast speeds if the need arises. Groups of males sometimes perform acrobatic stunts for a female’s attention,

Nutrition
The manta ray is a filter feeder. It scoops in water and food through the mouth. Modified denticles on each gill arch filter plankton, fish and larvae from the water. They are bottom feeders, catching their prey on gill rakers. These rusty-coloured, spongy, flat plates of tissue fill the spaces between the gill bars. Around 20 to 30 kg (44 to 66 pound) of plankton may be ingested daily.

Manta Ray 2

On either side of the mouth, fleshy projections filter prey into the opening. These projections or lobes are closed or furled in front of the mouth when not feeding. Slow vertical loops when feeding are believed to concentrate prey.

Reproduction
Males may follow a female for up to half an hour. Mating patterns seem to be triggered by a full moon. Other males follow the first male in a 'mating train'. Mating takes place just below the surface. The male bites the pectoral fin, inserts the claspers into the cloaca and stays in place for a minute or two. The eggs may stay in the female for as long as 12 months. The eggs hatch internally and eventually the female has two young (on average). There may be a two year gap before she gives birth again. This process of hatching eggs inside the mother’s body is known as ovoviviparity.

Threats
The main natural threats to the manta ray are large sharks and, occasionally, orcas. Fishing and use of body parts, especially gill rakers, in Chinese medicines, has also resulted in a decline in manta ray populations. There is no data on manta rays being a significant form of by-catch from commercial fishing operations, certainly not in Australia. As they are more likely to be found near shallower waters, there doesn’t seem to be too many rays lost through misadventures with fishing nets and trawlers.

Threats are most likely to take the form of activities or processes which impact on water quality or which disturb the habitat in which they live.

Conservation
Because of their size, manta rays are rarely kept in captivity. However there are a few. Nandi now resides in a 6.2 million gallon exhibit, the Ocean Voyager, at Georgia Aquarium after outgrowing her previous home at uShaka Marine World, Durban, South Africa.

In Okinawa Churaumi Aquarium, several manta rays have been born in captivity.

In 2011, the manta ray was included in the Convention of Migratory Species of Wild Animals (CMS) and is now strictly protected on a global scale. The International Union for Conservation of Nature (IUCN) has listed the giant manta ray as ‘vulnerable with an elevated risk of extinction’. This happened in October 2011.

The manta ray can be seen in the wild at the world heritage listed Ningaloo Reef off Western Australia's coast.

 

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Comments

Apr 2, 2012 4:37am
askformore
The Manta Ray is very elegant when it moves. Thank you for a beautiful article. Thumbs up!
Apr 2, 2012 5:10am
JudyE
Thanks askformore. Glad you enjoyed it. They are something special, aren't they?
Apr 10, 2012 6:00am
eileen
Very interesting article on the Manta ray I have learned more from this. Great pictures too. It amazes me how people swim with rays especially after the Australian croc guy (just cannot think of his name at moment) was killed through one.
Apr 10, 2012 8:55am
JudyE
Hi Eileen. Glad you enjoyed the article. Steve Irwin (if that's who you are thinking of) died from a barb from a stingray which is a bit different. The manta ray doesn't have a stinger so is not a danger to swimmers.
Apr 10, 2012 7:12pm
aidenofthetower
I was going to say the same thing. :-P I also wanted to add that while getting stung by a sting ray isn't fun, it very rarely results in fatality. It really was a freak accident that Steve Irwin died of the sting ray. If it wouldn't have punctured his heart it is very unlikely that it would have killed him and some even say that if he hadn't of pulled the barb out on the boat he may have survived. These sorts of accidents are very rare (just like shark attacks are rare considering the number of people, the number of sharks, and how often people swim with sharks).
Apr 10, 2012 1:11pm
Deborah-Diane
Fascinating article! Thanks for the info. One of our daughters has going swimming with manta rays on a trip. I was glad to read more about them!
Apr 10, 2012 6:34pm
JudyE
Thanks Deb. A couch-surfer who staye with us and dived with them in West Aust was blown away with the experience. They were all given a video of their swim. There were quite strict regulations on how close they could get etc which was good.
Apr 10, 2012 7:07pm
aidenofthetower
Very cool article about manta rays. They are so beautiful in a weird kinda way as they gracefully "fly" through the waters. Thanks!
Apr 10, 2012 8:19pm
JudyE
Thanks for the comments Aidenofthetower. It's always nice to know someone liked an article.
May 11, 2012 3:25pm
Misskate
We recently went to Sea World, and they have a tank there where you can touch them, i was very surprised at how soft they were. Still a bit scary, but they were actually coming up to the surface to be touched, although in the wild this would be very dangerous. Interesting article. :)
May 26, 2012 12:54am
adragast
I saw them in Okinawa! The way they move is effectively fascinating.
May 26, 2012 2:54am
toebunkers
I've seen them a few times in sea life centres. They are so graceful when they swim. Liked the article!
May 26, 2012 7:01am
JudyE
Thanks for the comments, folks.
Misskate - sorry I didn't reply sooner. Somehow I missed your comment.
I find the size of them quite incredible. A friend swam with them and said when it swam over the top of her, the whole area just went black. Glad you enjoyed the article.
May 27, 2012 5:21am
Jack_Luca
What a beautiful animal. I would love to swim with manta rays. I like the way they move -- they almost remind me of butterflies. Pinning this!
May 27, 2012 6:58am
JudyE
Thanks very much Jack - and also for pinning it. I'm pleased you enjoyed the article.
May 27, 2012 10:55am
Sherlockian
Great, informative article! I really love sea creatures. : )
May 30, 2012 10:37pm
cabmgmnt
Had hands on experience with manta rays in the Florida Keys.They are magnificent!
May 31, 2012 1:00am
JudyE
Thanks Sherlockian and cabmgmnt. It's kind of you both to comment. Lucky you cabmgmnt - having hands on! I bet you won't forget that for a while!
Feb 26, 2013 8:18pm
aguy
Manta Rays are beautiful. It is amazing that something that big can survive by being a filter feeder. I can watch them all day!
Mar 9, 2013 10:57pm
JudyE
Thanks for the comment, aguy. Sorry for the late response. We've been away. Manta rays are certainly fascinating.
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