MANTA RAY: CHARACTERISTICS, HABITAT, FEEDING, REPRODUCTION - BIOLOGY - 2025

The manta ray or giant manta (Manta birostris) is an elasmobranch belonging to the Mobulidae family. In this species its large pectoral fins stand out, which are shaped like a triangle and can measure up to 6.8 meters.

In addition, it has two cephalic fins, located on both sides of its mouth. To feed, these can be deployed, to channel as much water as possible into the oral cavity.

Stingray. Source: jon hanson from london, UK

Their skin is thick and in the dorsal region it is dark, and may be black, or grayish blue, with white spots on the “shoulders”. In contrast, the belly is white. A characteristic of this animal is the mouth. This is black and is located terminally, on the top of the head.

Regarding its distribution, it lives in temperate, tropical and subtropical waters worldwide, between latitudes 35 ° S and 35 ° N. They usually live at great depths, but nevertheless, they can be located in coastal regions

This cartilaginous fish does not rest on the ocean floor, as many flatfish do. This is because it needs to swim continuously, in order for water to enter its gills and in this way it can breathe.

Migration

The giant manta is a migratory species. In addition, it is usually a stationary visitor along the entire coastline, near underwater pinnacles, on the high seas and on some oceanic islands.

The length of stay in these regions may be associated with zooplankton abundance, tidal patterns and circulation, mating, and seawater temperature.

This is supported by significant seasonal sightings north of New Zealand, on the west coast of the United States, Uruguay and in the Similan Islands.

In investigations carried out, where satellite tracking and photo identification were used, the large migrations of Manta birostris are evident, at a distance greater than 1,100 kilometers. Thus, movements were registered from Mozambique to South Africa, with a total of 1,100 kilometers.

Also, it travels from Ecuador to Peru, with an approximate journey of 190 kilometers and from Yucatan to the Gulf of Mexico, traveling a distance of 448 kilometers.

I swim

Nanosanchez

The giant manta ray can swim alone or in groups, cruising slowly through the ocean. However, in some cases it has the ability to do so at a higher speed, as well as to dive to a depth of 1,000 meters.

Movement patterns

There are two models of swimming, which are related to the pectoral fins. One of these is wave locomotion. In it, the waves extend to the underside of the pectoral fins, from the anterior to the posterior area of ​​said body structure.

The other type of displacement is known as oscillatory, where these fins move up and down. This type of swim could be considered as a flight under water, with flapping being a movement analogous to the flight that birds make.

From the anatomical point of view, the pectoral girdle and the morphological configuration of the fins intervene in these movements. In addition, the muscles and a highly specialized nervous system take part, which can perfectly synchronize all movements.

Evolution

jon hanson from london, UK

The skeleton of the manta ray is cartilaginous, so conservation is more difficult than that of those animals that have bones. However, in some regions of North America fossil records have been located, dating back to the Oligocene, Miocene, and Pliocene periods.

Although the data on the evolution of this animal are not abundant, the specialists consider them quite clear. The first elasmobranchs inhabited the planet approximately 395 million years ago, in the mid-Devonian.

Based on analyzes of the fossilized samples, they likely arose from placoderms and spiny sharks. The first genus of the group of primitive sharks is known as Cladoselache. These include a species with smooth teeth, gills and a carnivorous diet, characteristics very similar to current elasmobranchs.

In the Silurian period, around 421 million years ago, the Elasmobranchii and Holocephala classes separated. Thus, the differentiation of chimeras with sharks occurred.

Adaptations

Data on the evolution of rays suggest that they originated from sharks, 170 million years ago. During the Carboniferous period, rays had separated from sharks. This stage was highly productive for cartilaginous fish, because they diversified abundantly.

The primitive rays, which were already abundant in the seas during the Jurassic period, progressively developed a series of adaptations that allowed them to develop on the seabed.

In this sense, the Cyclobatis is considered one of the first genera. Its body was circular and it had a tail with a sharp stinger.

The rays that originated the manta rays, approximately 20 million years ago, were benthic. In addition, to swim, they performed wave movements.

Today's manta rays evolved around 5 million years ago. Their large and triangular pectoral fins, a distinctive aspect of this group, gradually developed.

Likewise, the dangerous stinger present in the stripes, disappeared. However, they kept their elongated body and long tail, similar to a whip.

Habitat and distribution

jon hanson from london, UK

The giant manta is widely distributed in temperate and tropical waters globally. In the northern hemisphere, it can be found on the west and east coasts of the United States, in New Jersey and in California, respectively.

Also, it lives in Aomori and in the bay of Mutsu (Japan), Sinai (Egypt) and in the Azores islands. Likewise, she lives in countries of the southern hemisphere, such as New Zealand, South Africa, Uruguay and Peru.

In some regions, such as Mozambique, the habitat overlaps that of Manta alfredi. However, they exhibit different uses of space and have their own scrolling patterns.

Manta birostris could behave like a seasonal visitor, sighted at specific times of the year. This occurs in some places of aggregation, such as in the North Island (New Zealand), in the Similan Islands (Thailand), in Isla de la Plata (Ecuador), the Laje de Santos marine park (Brazil) and in Holbox Island in Mexico.

Also, there is a group that presents a certain degree of philopatry with some regions. An example of this is the frequency of these animals on Socorro Island (Mexico), Malpelo Island (Colombia), Coco Island (Costa Rica), Laje de Santos (Brazil) and Galapagos Island in Ecuador.

Habitat

The Manta birostris lives in subtropical, temperate and tropical waters of the Pacific, Atlantic and Indian oceans. This species spends much of its life traveling with the currents. Likewise, it migrates to areas where the water is rich in nutrients, thus increasing the possibility of capturing zooplankton.

It could be located in cold waters, with a temperature of 19 ° C. However, the preference for certain temperatures may vary by region.

In this regard, on the east coast of the United States, this species lives in waters of 19 ° C to 22 ° C. On the contrary, in Indonesia and Yucatan, they are found in bodies of water with a temperature between 25 and 30 ° C.

Likewise, they can be distributed in estuarine waters, close to oceanic entrances. This is possibly for the purpose of using them as breeding areas.

Furthermore, this species can be seen in seamounts and pinnacles offshore, on shallow reefs, and occasionally on seagrass beds and sandy bottoms. Also, you could visit areas near the coast, where the prey that make up its diet abound.

Feeding

The manta ray is a filter feeder animal, as well as a macro predator. At the water surface level, it consumes a large amount of zooplankton, while in the depths it hunts medium and small fish.

Among the planktonic organisms that they consume are the larvae of decapods, euphausiids, copepods, crabs and mysids. Also, some fish eggs and ketognaths are included in their diet.

The Manta birostris could show plasticity in the use of the different depths of the water where it lives.

In relation to this, it could navigate shallow waters, less than 10 meters. Also, studies show that this cartilaginous fish dives between 200 and 450 meters and dive to more than 1000 meters.

Filtering process

When filter feeding, it unwinds the head fins. In this way, it helps more water enter the mouth. The filter is located in the throat portion.

This structure is made up of a series of cartilaginous tubules located in a parallel way, between which there are small holes. These lobes direct the water to a turbulent flow, before it is expelled from the fish's mouth.

Large particles are filtered. However, much of the plankton is so small that it could slip between the gaps, while other types can bounce off the tubules. Thus, they reach the esophagus and are swallowed.

Finally, the water where the nutrients were found, leaves the mouth through the oropharyngeal cavity, through the gill slits.

Feeding method

The giant blanket uses different techniques to obtain its food. Thus, it seeks to maximize plankton intake, while minimizing energy expenditure related to the hunting and trapping process.

One of these strategies is to create a kind of food chain with other blankets. When they swim together at high speed, a kind of cyclone forms, thus maximizing food intake.

Also, they can swim slowly around the prey, thus agglomerating the planktonic species in a group. After this, she accelerates her swim and goes through the pool with her mouth open. If the mass of plankton is very dense, the stingray may make an abrupt leap over it.

When the stingray feeds alone, it usually stands upright while rolling backward. Also, it can ingest both the plankton that is settled below the surface of the water, and that found on the seabed, covered by sand.

Another technique is “cyclonic” feeding, where up to 150 giant manta rays swim together, in a spiral fashion. Thus, a column of water is created that operates like a centrifuge, throwing the plankton out.

Reproduction

The female has a uterus and the male has two structures similar to the penis, known as claspers. These sperm transmitting organs develop in the inner pelvic part and have an opening through which this fluid exits and is transferred to the female.

In relation to sexual maturity, the female can reach it when she is 6 to 8 years old, while in the male it occurs between 5 and 6 years of age.

Some specialists estimate that one of the signs of being able to reproduce is the width of the disc. In the case of the male, its dimension could be 380 centimeters and in the female it could be 413 centimeters. This could vary in the habitats where it is found.

Thus, for example, in Mozambique the male matures when his disk measures around 400 centimeters and the female matures when it measures more than 400 centimeters.

Courtship

The moment the Manta birostris can mate, the female excretes a chemical known as a pheromone. This is captured by the male, alerting him to the reproductive status of the female, thus being able to locate and follow her.

The courtship of this species is known as "the train of the stingray." This is because several males are chasing a female at the same time to try to mate.

When a male is successful, he bites the female on her pectoral fin. Having firmly grasped her, he turns around, pressing his body against hers. At that time, she inserts one of her claspers into the female's cloaca, staying together for 60 to 90 seconds.

Mating

Before the sperm is transmitted, the gland at the base of the classicper secretes a dense fluid, made up of lipids and proteins. Specialists attribute a lubricating function of the male copulatory organ to it. Also, this fluid could prevent the loss of sperm during copulation.

While the clasper pushes the seminal fluid into the female's body, the male continues to cling to the pectoral fin for a few more minutes, while both continue to swim together.

Fertilized eggs hatch inside the female, for a period of 9 to 12 months. Embryos develop in the uterus, but placental formation does not occur.

To feed, they initially do so from the yolk and after hatching, they receive nutrients from a substance known as histotroph or uterine milk.

This is rich in low molecular weight metabolites, glycogen and fat. It is produced by glandular trophonemes, villi that exist on the inner surface of the uterus.

Without the presence of the placenta and umbilical cord, the embryo obtains oxygen through oral pumping. In this process, open and close your mouth repeatedly, performing a rhythmic breathing.

The babies

The birth of one or two young at a time occurs in shallow waters, where the young may remain for a long time, before moving away from the coast.

The newborn weighs approximately 9 kilograms and its disk is 1.4 meters wide. According to its size, it is one of the largest within the elasmobranch group.

The manta ray is born wrapped by its pectoral fins, but in a short time it can swim alone. They do it first in shallow waters and then in deeper ones.

State of conservation

Manta birostris is part of the group of animals protected by the IUCN. This is because in the last 20 years its population has drastically decreased.

The fact that this species is considered vulnerable to extinction raises the alarm worldwide. In this way, actions have been generated in order to investigate the causes of the problem and the actions to be taken to solve the situation.

-Causes

Habitat destruction

In the different stages of the life of the manta ray, the coral reefs play a very important role. This is because they provide a breeding area, food and are cleaning stations.

Due to ocean acidification, a product of high levels of CO2 in the atmosphere, the chemistry of the seas has changed. This results in corals not being able to form the calcite crystals that make up their skeletons.

Therefore, reef disturbances pose a serious threat to the giant manta. Another factor that affects this cartilaginous fish is oil spills, which degrade the habitat and alter the different aquatic biomes.

Plastics intake

Worldwide, the production of plastics has increased disproportionately and with this, waste. According to some research, between 4.8 and 12.7 million tons of waste reach the oceans annually.

The giant blanket is a filter feeder animal, so it is likely to ingest plastic debris, including microplastics, in this way. This brings serious consequences to the animal, including its death.

Climate change

Recent studies indicate that the Manta birostris is one of the pelagic species most vulnerable to climatic variations. The main reason is that plankton, one of its primary sources of nutrients, is adversely affected by changing sea temperatures.

Fishing

artisanal fishing

In some regions, such as Mozambique and Tasmania, there is artisanal fishing for manta rays. This is done through trawl nets and longlines. Also, due to their slow swim, some can be harpooned.

The meat is generally consumed dry and is part of various traditional dishes of the town.

All along the coast of Ghana there is a seasonal fishing, as the giant manta goes to this area in search of food.

Incidental fishing

These animals are often caught in steel and gill nets, as is the case in purse seine fishing for tuna in the oceanic waters of the Atlantic. Also, on the beaches of KwaZulu-Natal (South Africa), the manta ray is caught accidentally in shark protection nets.

In the Machalilla National Park, in Ecuador, the illegal use of the trawl gear to fish for Acanthocybium solandri, results in the capture of the Manta birostris.

Directed fishing

This species is highly valued in the international market. Gill filter plates are used in the manufacture of some traditional Asian medicines. Likewise, meat is sold as food and liver is used in medicine.

Thus, this elasmobranch is captured, despite the fact that in many countries doing so is an illegal activity. To do this, hunters use their slow swimming speed, their large size and their gregarious behavior.

In addition, this is also influenced by the easy prediction of the habitat where it is found and how friendly it could be to the human presence.

Actions

Manta birostris is legally protected in many countries, such as Hawaii, Maldives and New Zealand, where since 1953 it has been under the protection of the Wildlife Law.

Likewise, it is included in the Convention on Migratory Species. This intergovernmental treaty is covered by the United Nations Environment Program. It currently has more than 100 signatory countries from Central and South America, Africa, Europe, Oceania and Asia.

Behavior

Jumps

The giant blanket is an animal that can weigh up to 2 tons. However, it is capable of jumping out of the water. Thus, it can jump and land on its head or do it forward and sink into the sea, first inserting its tail.

Also, when getting out of the water, you can do a movement similar to a somersault. When found in groups, each stingray executes this aerial maneuver, one after another.

Such particular movements in a fish could be associated as part of courtship behaviors. Likewise, they are used to escape from a predator or as a demonstration of strength, by males.

Also, they serve to eliminate parasites attached to your body or commensal remoras.

Some researchers indicate that these stunts can possibly be used as a communicative element. This is because when the animal's body collides with the water it produces a loud noise, which could be heard from a long distance.

Cleaning

Manta birostris can be affected by various marine parasites. Also, it suffers bites from its predators, consisting of killer whales and sharks. Due to this, on some occasions this elasmobranch visits “cleaning stations”, located on coral reefs.

Small fish, such as butterflyfish, live in these areas, feeding on dead or parasite-infected meat. For this, the manta ray adopts a stationary position for several minutes, while the fish consume the dead skin.

Another symbiotic interaction is with the remora fish. This travels attached to the giant blanket, thus feeding on its parasites and plankton.

Social behavior

The manta ray has solitary habits, but nevertheless, on several occasions it forms groups. For example, during courtship, large numbers of males often swim together behind a female. Also, during the reproductive period, the couple can spend a long time together.

Giant manta rays often form large groups to hunt or around areas where plankton abound. Similarly, when they migrate, up to 50 giant mantas can gather, swimming in a straight line in the ocean.

In these social interactions there is no territoriality or hierarchy. M. birostris can share its habitat with other filter feeders, such as the whale shark and blue whale.

Sting and toxicity

The stingray evolved from the stingray, so they have a very similar, long and thin tail, similar to a whip. However, there is a big difference: Manta birostris lacks the thorn or stinger and the venom gland, which are present in the stingray.

For this reason, the giant blanket is not dangerous for humans, as far as bites are concerned. However, its large size and stingray-like appearance could intimidate people.

Although the giant manta is unlikely to come close to divers, it can show some aggressiveness if it feels threatened or is caught in a net.

References

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9. Threatened, Species Pursuant to the Endangered Species Act and for the Concurrent Designation of Critical Habitat. Recovered from defenders.org.
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