![M](https://upload.wikimedia.org/wikipedia/commons/2/27/M._Birostris_swimming_with_a_diver.jpg)
The giant oceanic manta ray, giant manta ray, or oceanic manta ray (''Mobula birostris'') is a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
of
ray
Ray may refer to:
Fish
* Ray (fish), any cartilaginous fish of the superorder Batoidea
* Ray (fish fin anatomy), a bony or horny spine on a fin
Science and mathematics
* Ray (geometry), half of a line proceeding from an initial point
* Ray (gr ...
in the
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Mobulidae
The Mobulidae (manta rays and devilfishes) are a family of rays consisting mostly of large species living in the open ocean rather than on the sea bottom.
Taxonomy
The Mobulidae have been variously considered a subfamily of the Myliobatidae by ...
, and the largest type of ray in the world. It is circumglobal and is typically found in tropical and subtropical waters, but can also be found in temperate waters.
Until 2017, the species was classified in the genus ''Manta'', along with the smaller
reef manta ray
The reef manta ray (''Mobula alfredi'')
is a species of ray in the family Mobulidae, one of the largest rays in the world. Among generally recognized species, it is the second-largest species of ray, only surpassed by the giant oceanic manta r ...
(''Mobula alfredi''). DNA testing revealed that both species are more closely related to rays of the genus ''Mobula'' than previously thought. As a result, the giant manta was renamed as ''Mobula birostris'' to reflect the new classification.
Description
![Manta birostris-Thailand](https://upload.wikimedia.org/wikipedia/commons/6/6e/Manta_birostris-Thailand.jpg)
The giant oceanic manta ray can grow up to in maximum length and to a disc size of across with a weight of about
but average size commonly observed is .
It is dorsoventrally flattened and has large, triangular
pectoral fins
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as see ...
on either side of the disc.
At the front, it has a pair of cephalic fins which are forward extensions of the
pectoral fins
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as see ...
. These can be rolled up in a spiral for swimming or can be flared out to channel water into the large, forward-pointing, rectangular mouth when the animal is feeding.
The teeth are in a band of 18 rows and are restricted to the central part of the lower jaw.
The eyes and the
spiracles are on the side of the head behind the cephalic fins, and the
gill slits are on the
ventral
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
(under) surface.
It has a small dorsal fin and the tail is long and whip-like. The manta ray does not have a spiny tail as do the closely related
devil rays (''Mobula'' spp.) but has a knob-like bulge at the base of its tail.
[Stevens, Guy (2011]
"Field guide to the identification of Mobulid rays (Mobulidae)"
. Manta Trust.
The skin is smooth with a scattering of conical and ridge-shaped
tubercle
In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal.
In plants
A tubercle is generally a wart-like projection ...
s. The colouring of the
dorsal
Dorsal (from Latin ''dorsum'' ‘back’) may refer to:
* Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism
* Dorsal, positioned on top of an aircraft's fuselage
* Dorsal c ...
(upper) surface is black, dark brown, or steely blue, sometimes with a few pale spots and usually with a pale edge. The ventral surface is white, sometimes with dark spots and blotches. The markings can often be used to recognise individual fish.
''Mobula birostris'' is similar in appearance to ''
Mobula alfredi
The reef manta ray (''Mobula alfredi'')
is a species of ray in the family Mobulidae, one of the largest rays in the world. Among generally recognized species, it is the second-largest species of ray, only surpassed by the giant oceanic manta r ...
'' and the two species may be confused as their distribution overlaps. However, there are
distinguishing features
''Distinguishing Features'' (german: Besondere Kennzeichen) is a German silent crime film directed by Edmund Heuberger. It was shot at the Staaken Studios in Berlin. The film's sets were designed by Gustav A. Knauer and Willy Schiller
Willy ...
.
Physical distinctions between oceanic manta ray and reef manta ray
![Giant Manta AdF](https://upload.wikimedia.org/wikipedia/commons/f/fc/Giant_Manta_AdF.jpg)
The oceanic manta ray is larger than the
reef manta ray
The reef manta ray (''Mobula alfredi'')
is a species of ray in the family Mobulidae, one of the largest rays in the world. Among generally recognized species, it is the second-largest species of ray, only surpassed by the giant oceanic manta r ...
, 4 to 5 metres in average against 3 to 3.5 metres. However, if the observed rays are young, their size can easily bring confusion. Only the colour pattern remains an effective way to distinguish them. The
reef manta ray
The reef manta ray (''Mobula alfredi'')
is a species of ray in the family Mobulidae, one of the largest rays in the world. Among generally recognized species, it is the second-largest species of ray, only surpassed by the giant oceanic manta r ...
has a dark dorsal side with usually two lighter areas on top of the head, looking like a nuanced gradient of its dark dominating back coloration and whitish to greyish, the longitudinal separation between these two lighter areas forms a kind of "Y". While for the oceanic manta ray, the dorsal surface is deep dark and the two white areas are well marked without gradient effect. The line of separation between these two white areas form meanwhile a "T".
Difference can also be made by their ventral coloration, the
reef manta ray
The reef manta ray (''Mobula alfredi'')
is a species of ray in the family Mobulidae, one of the largest rays in the world. Among generally recognized species, it is the second-largest species of ray, only surpassed by the giant oceanic manta r ...
has a white belly with often spots between the
branchial gill slits and other spots spread across trailing edge of
pectoral fins
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as see ...
and abdominal region. The oceanic manta ray has also a white ventral coloration with spots clustered around lower region of its abdomen. Its cephalic fins, inside of its mouth and its gill slits are often black.
Distribution and habitat
The giant oceanic manta ray has a widespread distribution in tropical and temperate waters worldwide. In the
Northern Hemisphere
The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...
, it has been recorded as far north as southern California and New Jersey in the United States,
Aomori Prefecture
is a prefecture of Japan in the Tōhoku region. The prefecture's capital, largest city, and namesake is the city of Aomori. Aomori is the northernmost prefecture on Japan's main island, Honshu, and is bordered by the Pacific Ocean to the eas ...
in Japan, the
Sinai Peninsula
The Sinai Peninsula, or simply Sinai (now usually ) (, , cop, Ⲥⲓⲛⲁ), is a peninsula in Egypt, and the only part of the country located in Asia. It is between the Mediterranean Sea to the north and the Red Sea to the south, and is a ...
in Egypt, and the
Azores
)
, motto =( en, "Rather die free than subjected in peace")
, anthem= ( en, "Anthem of the Azores")
, image_map=Locator_map_of_Azores_in_EU.svg
, map_alt=Location of the Azores within the European Union
, map_caption=Location of the Azores wi ...
in the northern Atlantic. In the Southern Hemisphere, it occurs as far south as Peru, Uruguay, South Africa, and New Zealand.
It is an ocean-going species and spends most of its life far from land, travelling with the currents and migrating to areas where upwellings of nutrient-rich water increase the availability of
zooplankton
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
. The oceanic manta ray is often found in association with offshore oceanic islands.
[
]
Evolution
Captivity
There are few public aquariums with giant manta ray in captivity. Since 2009, captive manta rays have been classified as ''Ꮇ. alfredi'' and there have been no facilities to display ''Ꮇ. birostris'' for some time.
Since late 2018 it has been exhibited at Nausicaä Centre National de la Mer in France and Okinawa Churaumi Aquarium
The , formerly known as the Okinawa Ocean Expo Aquarium, is located within the Ocean Expo Park in Okinawa, Japan. It is a member of the Japanese Association of Zoos and Aquariums (JAZA), and was the largest aquarium in the world until it was sur ...
in Japan.
There are also reports that they were kept at the Marine Life Park
The Marine Life Park is a part of Resorts World Sentosa, Sentosa, situated in southern Singapore. The 8-hectare (20-acre) park houses two attractions, the S.E.A. Aquarium and the Adventure Cove Waterpark, and featured the largest oceanarium in ...
, part of the Resorts World Sentosa
Resorts World Sentosa ( abbreviation: RWS) is an integrated resort on the island of Sentosa, which is located off the southern coast of Singapore. The key attractions within RWS include one of Singapore's two casinos, a Universal Studios Sing ...
in Singapore
Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, bor ...
.
Biology
When traveling in deep water, the giant oceanic manta ray swims steadily in a straight line, while further inshore it usually basks or swims idly around. Mantas may travel alone or in groups of up to 50 and sometimes associate with other fish species, as well as sea bird
Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same enviro ...
s and marine mammal
Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They are an informal group, unified only by their ...
s. About 27% of their diet is based on filter feeding
Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...
, and they will migrate to coastlines to hunt varying types of zooplankton such as copepod
Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic (inhabiting sea waters), some are benthic (living on the ocean floor), a number of species have ...
s, mysids, shrimp
Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are ref ...
, euphausiids, decapod larvae, and on occasion, varying sizes of fish. When foraging, it usually swims slowly around its prey, herding the planktonic creatures into a tight group before speeding through the bunched-up organisms with its mouth open wide. While feeding, the cephalic fins are spread to channel the prey into its mouth and the small particles are sifted from the water by the tissue between the gill arches. As many as 50 individual fish may gather at a single, plankton-rich feeding site.[ Research published in 2016 proved about 73% of their diet is mesopelagic (deep water) sources including fish. Earlier assumptions about exclusively filter feeding were based on surface observations.
The giant oceanic manta ray sometimes visits a ]cleaning station
A cleaning station is a location where aquatic life congregate to be cleaned by smaller creatures. Such stations exist in both freshwater and marine environments, and are used by animals including fish, sea turtles and hippos, referred to as cli ...
on a coral reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of Colony (biology), colonies of coral polyp (zoology), polyps held together by calcium carbonate. Most coral reefs are built from stony corals, wh ...
, where it adopts a near-stationary position for several minutes while cleaner fish
Cleaner fish are fish that show a specialist feeding strategy by providing a service to other species, referred to as clients, by removing dead skin, ectoparasites, and infected tissue from the surface or gill chambers. This example of cleaning ...
consume bits of loose skin and external parasites
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...
. Such visits occur most frequently at high tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another.
Tide tables ...
. It does not rest on the seabed as do many flat fish
A flatfish is a member of the ray-finned demersal fish order Pleuronectiformes, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migratin ...
, as it needs to swim continuously to channel water over its gill
A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they ar ...
s for respiration
Respiration may refer to:
Biology
* Cellular respiration, the process in which nutrients are converted into useful energy in a cell
** Anaerobic respiration, cellular respiration without oxygen
** Maintenance respiration, the amount of cellul ...
.
Males become sexually mature when their disc width is about , while females need to be about wide to breed. When a female is becoming receptive, one or several males may swim along behind her in a "train". During copulation
Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetra ...
, one of the males grips the female's pectoral fin with his teeth and they continue to swim with their ventral surfaces in contact. He inserts his claspers
In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating.
Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's c ...
into her cloaca and these form a tube through which the sperm is pumped. The pair remains coupled together for several minutes before going their own way.
The fertilized eggs
Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...
develop within the female's oviduct
The oviduct in mammals, is the passageway from an ovary. In human females this is more usually known as the Fallopian tube or uterine tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, o ...
. At first, they are enclosed in an egg case and the developing embryos feed on the yolk
Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example ...
. After the egg hatches, the pup remains in the oviduct and receives nourishment from a milky secretion.[ As it does not have a ]placenta
The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mate ...
l connection with its mother, the pup relies on buccal pumping
Buccal pumping is "breathing with one's cheeks": a method of ventilation used in respiration in which the animal moves the floor of its mouth in a rhythmic manner that is externally apparent.Brainerd, E. L. (1999). New perspectives on the evolutio ...
to obtain oxygen. The brood size is usually one but occasionally two embryos develop simultaneously. The gestation period is thought to be 12–13 months. When fully developed, the pup is in disc width, weighs and resembles an adult. It is expelled from the oviduct, usually near the coast, and it remains in a shallow-water environment for a few years while it grows.
Brain size and intelligence
The oceanic manta has one of the largest brains, weighing up to 200 g, (five to ten times larger than a whale shark brain) and the largest brain-to-mass ratio of any fish. It heats the blood going to its brain and is one of the few animals (land or sea) that might pass the mirror test
The mirror test—sometimes called the mark test, mirror self-recognition (MSR) test, red spot technique, or rouge test—is a behavioral technique developed in 1970 by American psychologist Gordon Gallup Jr. as an attempt to determine whether an ...
, seemingly exhibiting self-awareness.
Status and threats
Natural predation
Because of its large size and velocity in case of danger (24 km/h escape speed), the oceanic manta ray has very few natural predators that could be fatal to it. Only large sharks and dolphins, such as the tiger shark
The tiger shark (''Galeocerdo cuvier'') is a species of requiem shark and the last extant member of the family Galeocerdonidae. It is a large macropredator, capable of attaining a length over . Populations are found in many tropical and tempera ...
(''Galeocerdo cuvier''), the great hammerhead shark (''Sphyrna mokarran''), the bullshark (''Carcharhinus leucas''), the false killer whale
The false killer whale (''Pseudorca crassidens'') is a species of oceanic dolphin that is the only extant representative of the genus '' Pseudorca''. It is found in oceans worldwide but mainly in tropical regions. It was first described in 184 ...
(''Pseudorca crassidens''), and the killer whale
The orca or killer whale (''Orcinus orca'') is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. It is the only extant species in the genus ''Orcinus'' and is recognizable by its black-and-white ...
(''Orcinus orca''), are capable of preying on the ray. Nonlethal shark bites are very common occurrences, with a vast majority of adult individuals bearing the scars of at least one attack.
Fishery
The oceanic manta ray is considered to be endangered
An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and in ...
by the IUCN’s Red List of Endangered Species
The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biologi ...
because its population has decreased drastically over the last twenty years due to overfishing. Because ''M. birostris'' feeds in shallow waters, there is a higher risk of them getting caught in fishing equipment, especially in surface drift gillnets and bottom set nets. Whatever the type of fishing (artisanal, targeted or bycatch), the impact on a population which has a low fecundity rate, a long gestation period with mainly a single pup at a time, and a late sexual maturity can only be seriously detrimental to a species that cannot compensate for the losses over several decades.
Since the 1970s, fishing for manta rays has been significantly boosted by the price of their gill rakers on the traditional Chinese medicine market. In Chinese culture, they are the main ingredient in a tonic that is marketed to increase immune system function and blood circulation, though there is no strong evidence that the tonic is actually beneficial to health. For this reason and others, gill rakers are sold at relatively high prices – up to $400 per kilogram – and are sold under the trade name ''pengyusai''. In June 2018 the New Zealand Department of Conservation
An environmental ministry is a national or subnational government agency politically responsible for the environment and/or natural resources. Various other names are commonly used to identify such agencies, such as Ministry of the Environment ...
classified the giant oceanic manta ray as "Data Deficient" with the qualifier "Threatened Overseas" under the New Zealand Threat Classification System.
Pollution
There is also the threat of microplastics
Microplastics are fragments of any type of plastic less than in length, according to the U.S. National Oceanic and Atmospheric Administration (NOAA) and the European Chemicals Agency. They cause pollution by entering natural ecosystems from a v ...
in the diets of oceanic manta rays. A 2019 study in Indonesia's Coral Triangle was performed to determine if the filter-feeding megafauna of the area were accidentally ingesting microplastics, which can be eaten by filter-feeders either directly (by ingesting layers of plastic polymers that float on the surface of the water in feeding areas) or indirectly (by eating plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
that previously ate microplastics). The results of the study provided ample evidence that filter feeders, such as oceanic manta rays, that lived in the area were regularly consuming microplastics. Though it was also proven via stool samples that some of the plastic simply passed through the digestive systems of manta rays, the discovery is a concern because microplastics create sinks for persistent organic pollutants like dichloro-diphenyl-trichloroethanes (DDTs) and polycyclic aromatic hydrocarbon
A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. ...
s (PAHs). Manta rays that consume microplastics harboring these pollutants can suffer from a variety of health effects that range from short-term negative effects such as the reduction of bacteria in their guts, or long-term effects including pollutant-induced weakening of the population's reproductive fitness
Fitness (often denoted w or ω in population genetics models) is the quantitative representation of individual reproductive success. It is also equal to the average contribution to the gene pool of the next generation, made by the same individ ...
over future generations, which could negatively affect population levels of the rays in the future.
''M. birostris'' are also victims of bioaccumulation in certain regions. There has been at least one study that has shown how heavy metals such as As, Cd, and Hg can be introduced to the marine environment via pollution and can travel up the trophic chain. For example, there was a study in Ghana
Ghana (; tw, Gaana, ee, Gana), officially the Republic of Ghana, is a country in West Africa. It abuts the Gulf of Guinea and the Atlantic Ocean to the south, sharing borders with Ivory Coast in the west, Burkina Faso in the north, and To ...
that involved the testing of tissue samples from six ''M. birostris'' carcasses; all of them showed evidence of high concentrations of As and Hg (about 0.155–2.321 μg/g and 0.001–0.006 μg/g respectively). While the sample size was not the most ideal, it is a first step towards further understanding the true amount of bioaccumulation that ''M. birostris'' undergoes due to human pollution. These high levels of metals can cause harm to the people who consume ''M. birostris'', and could also cause health problems for the ''M. birostris'' species itself. More studies need to be done in order to further confirm the negative health effects of bioaccumulation on ''M. birostris''.
Climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
combined with rising temperatures, are projected to cause a 10% decrease in the global population of phytoplankton with a potential 50% decrease in tropical areas. With these reductions could come a decrease in ''M. birostris'' populations.
See also
* Threatened rays
References
External links
*
*
*
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Articles containing video clips
giant oceanic manta ray
The giant oceanic manta ray, giant manta ray, or oceanic manta ray (''Mobula birostris'') is a species of ray in the family Mobulidae, and the largest type of ray in the world. It is circumglobal and is typically found in tropical and subtropica ...
giant oceanic manta ray
The giant oceanic manta ray, giant manta ray, or oceanic manta ray (''Mobula birostris'') is a species of ray in the family Mobulidae, and the largest type of ray in the world. It is circumglobal and is typically found in tropical and subtropica ...
Pantropical fish
Fish of the Dominican Republic
Taxa named by Johann Julius Walbaum
Vulnerable fish