Sea devil (manta) — one of the largest fish in the world. Reaching a width of 8.8 m, manta rays are much larger than any other species of rays. For many decades there was only one known species, but scientists have divided it into two: oceanic, which prefers more open sea spaces, and reef, which is more coastal in nature. Now the giant manta ray is making a huge impact on tourism, creating a diving industry for tourists who want to swim along these gentle giants. Let's learn more about them.
View Origin and Description
The name “Manta” in Portuguese and Spanish means mantle (cloak or blanket). This is because the blanket-shaped trap has traditionally been used to catch rays. Historically, sea devils have been feared because of their size and strength. Sailors believed that they were dangerous to people and could sink boats by pulling on the anchors. This attitude changed around 1978 when divers in the Gulf of California found they were calm and people could interact with these animals.
Fun fact: Sea devils are also known as “cuttlefish” from — for their horn-shaped head fins, which give them an “evil” appearance. It was believed that they could sink a diver by wrapping him in their large “wings”.
Manta rays are members of the order Myliobatiformes, which consists of rays and their relatives. Sea devils developed from the lower slopes. M. birostris still has a vestigial remnant of a stinger in the form of a caudal spine. Manta rays — the only species of stingrays that have turned into filters. In a DNA study (2009), differences in morphology were analyzed, including color, phenogenetic variability, spine, skin teeth and teeth of different populations.
Two distinct species emerged:
- the smaller M. alfredi, found in the Indo-Pacific and tropical eastern Atlantic;
- large M. birostris found in tropical, subtropical and warm regions.
A 2010 DNA study near Japan confirmed morphological and genetic differences between M. birostris and M. alfredi. Several fossilized skeletons of manta rays have been found. Their cartilaginous skeletons do not retain well. Only three sedimentary beds are known to contain manta ray fossils, one from the Oligocene in South Carolina and two from the Miocene and Pliocene in North Carolina. They were originally described as Manta fragilis, but were later reclassified as Paramobula fragilis.
Appearance and Features
Sea devils move easily in the ocean thanks to their large pectoral “wings”. The manta birostris has tail fins and a small dorsal fin. They have two lobes of the brain that extend forward from the front of the head, and a wide, rectangular mouth containing small teeth exclusively in the lower jaw. The gills are located on the underside of the body. Manta rays also have a short, whip-like tail that, unlike many other rays, does not have a sharp barb.
Video: Sea Devil
Cubs of the Atlantic manta at birth weigh 11 kg. They grow very rapidly, doubling their body width from birth to the first year of life. Sea devils show slight dimorphism between the sexes with a wingspan of males ranging from 5.2 to 6.1 m and females ranging from 5.5 to 6.8 m. The largest specimen ever recorded was 9.1 m.
Interesting fact: Sea devils have one of the highest brain-to-body mass ratios and the largest brain size of all fish. that the entire skeleton is made of cartilage, allowing for a wide range of motion. These rays vary in color from black to greyish blue along the back and white underparts with greyish patches that are used to identify individual rays. The skin of the sea devil is rough and scaly, like most sharks.
Where does the sea devil live?
Sea devils are found in tropical and subtropical waters in all major oceans of the world (Pacific, Indian and Atlantic) and also enter temperate seas, typically between 35°N and South latitude. Their range includes the coasts of southern Africa, from southern California to northern Peru, from North Carolina to southern Brazil and the Gulf of Mexico.
The distribution area of giant manta rays is very extensive, although they are located in different parts of it in a fragmented way. They are commonly seen offshore, in ocean waters and near coastlines. Giant mantles are known to undergo long migrations and can visit colder waters for short periods of the year.
Fun fact: The fish that scientists have equipped with radio transmitters have traveled 1000 km from the place where they were caught and descended to depths of at least 1000 m. M. alfredi is a more resident and coastal species than M. birostris.
The sea devil stays closer to shore in warmer waters where food sources are plentiful, but can sometimes be found farther from shore. They are common near the coast from spring to autumn, but travel farther from the coast in winter. During the day they stay close to the surface and in shallow water, and at night they swim at great depths. Because of their wide range and sparse distribution across the world's oceans, there are still gaps in scientists' knowledge of the life history of giant devils.
Now you know where the sea devil stingray lives. Let's see what he eats.
What does the sea devil eat?
Manti are filter feeders. They constantly swim with large mouths open, filtering plankton and other small food from the water. To help with this strategy, giant manta rays have special valves known as cerebral lobes that help funnel more water and food into their mouths.
They swim slowly in vertical loops. Some researchers suggest that this is done in order to stay in the feeding area. Their large, gaping mouths and deployed brain lobes are used to herd planktonic crustaceans and small schools of fish. The manty filters the water through its gills and the organisms in the water are retained by the filtering device. The filtering adaptation consists of spongy plates at the back of the mouth, which are made of pinkish-brown tissue and extend between the supporting structures of the gills. The teeth of Manta birostris do not function during feeding.
Fun fact: With extremely high concentrations of food in manta feeding areas, they can, like sharks, succumb to food frenzy.
The basis of the diet is plankton and fish larvae. Sea devils are constantly moving after plankton. They use sight and smell to find food. The total weight of food eaten every day is about 13% of the weight. Manta rays leisurely swim around the prey, driving it into a heap, and then quickly swim with their mouths open through the accumulated marine organisms. At this time, the head fins, which are folded into a spiral tube, unfold during the feeding period, which helps the stingrays direct food into their mouths.
Character and Lifestyle Features
Manta rays are solitary, free swimmers that are not territorial. They use their flexible pectoral fins to gracefully swim across the ocean. The head fins of the sea devil are most active during the mating season. It has been recorded that mantas jump out of the water to a height of over 2 m, and then hit the surface. By doing this, the stingray can remove annoying parasites and dead skin from its large body.
In addition, sea devils visit a kind of “cleaning station”, where small remora fish (cleaners) swim near manti, collecting parasites and dead skin. Symbiotic interactions with sticky fish occur when they attach to and ride giant manta rays while feeding on parasites and plankton.
Fun fact: In 2016, scientists published a study that showed that sea devils exhibit behaviors associated with self-awareness. In a modified mirror test, individuals participated in contingency testing and unusual self-directed behavior.
Swimming behavior in mantas differs in different habitats: when traveling in depth, they move at a constant speed in a straight line, on the shore they usually bask or swim idle. Manta rays can travel alone or in groups of up to 50. They can interact with other fish species as well as seabirds and marine mammals. In a group, individuals can perform aerial jumps one after another.
Social Structure and Reproduction
Although giant manta rays are usually solitary animals, they come together to feed and mate. The sea devil becomes sexually mature at 5 years old. The mating season starts from the beginning of December and lasts until the end of April. Mating takes place in tropical waters (t 26-29 ° C) and around rocky reef zones 10-20 meters deep. Sea devil stingrays congregate in large numbers during the mating season, when several males court the same female. Males swim close behind the tail of the female at higher than usual speeds (9-12 km/h).
This courtship will last about 20-30 minutes, after which the female will decrease her swimming speed and the male will squeeze one side of the female's pectoral fin by biting it. He adjusts his body to the body of females. The male will then insert his clamp into the female's cloaca and inject his sperm, usually lasting about 90-120 seconds. The male then quickly swims away and the next male repeats the same process. However, after the second male, the female usually swims away, leaving the other males behind.
Fun fact: Giant sea devils have one of the lowest reproductive rates of any stingray lineage, typically giving birth to one fry every two to three years.
The gestation period for M. birostris is 13 months, after which females give birth to 1 or 2 live young. The babies are born wrapped in pectoral fins, but soon become free swimmers and fend for themselves. Manta puppies reach a length of 1.1 to 1.4 meters. There is evidence that sea devils live up to at least 40 years, but little is known about their growth and development.
Natural enemies of sea devils
manta rays have not developed much protection against predators, except for tough skin and a size that does not allow smaller animals to attack.
Only large sharks are known to attack rays, namely:
- bump-nosed shark;
- tiger shark;
- hammerhead shark;
- killer whales.
The greatest threat to stingrays is overfishing by humans, which is not evenly distributed across the oceans . It is concentrated in areas that provide the food resources it needs. Their distribution is very fragmented, so individual subpopulations are located at large distances, which does not give them the opportunity for mixing.
Both commercial and artisanal fisheries target the sea devil for its meat and other products. They are usually caught with nets, trawls and even harpoons. Many manta rays have been fished in California and Australia for their liver oil and skin. The meat is edible and eaten in some states, but less attractive than other fish.
Interesting fact: According to a study of fisheries in Sri Lanka and India, more than 1000 pieces of sea devils are sold annually in the fish markets of the country. By comparison, M. birostris populations in most key M. birostris sites worldwide are estimated to be well below 1,000 individuals.
The demand for their cartilage structures is driven by recent innovations in Chinese medicine. To meet the growing demand in Asia, target fishing has now developed in the Philippines, Indonesia, Madagascar, India, Pakistan, Sri Lanka, Mozambique, Brazil, Tanzania. Each year, thousands of rays, primarily M. birostris , are caught and killed solely for their gill arches.
Population and species status
The biggest threat to giant manta rays — this is a commercial business. Targeted manta ray fishing has significantly reduced populations. Due to their long lifespan and low reproduction rate, overfishing can seriously reduce local populations with little chance of replacement by individuals living elsewhere.
Fun Fact: While conservation measures have been put in place in many sea devil habitats, demand for manta ray arches and other body parts has skyrocketed in Asian markets. Fortunately, the interest of scuba divers and other tourists seeking to observe these large fish has also grown. This makes sea devils more valuable in living form than as fishermen's catch.
The tourism industry may provide more protection to the giant manta, but the value of the meat and for traditional medicinal purposes is still a danger to the species. Thus, it is important for scientists to continue to monitor manta populations to ensure the conservation of the species and to determine if other localized species exist.
In addition, sea devils are subject to other anthropogenic threats. Because manta rays must constantly swim to flush oxygen-rich water over their gills, they can become entangled and suffocate. These fish cannot swim backwards and their protruding head fins can cause them to become entangled in lines, nets, ghost nets and even mooring lines. Trying to free themselves, they become more entangled. Other threats or factors that may affect the number of manta rays are climate change, pollution from oil spills, and ingestion of microplastics.
Sea Devil Conservation
In 2011, manta rays became highly protected in international waters thanks to their inclusion in the Convention on Migratory Species of Wild Animals. Although manta rays are protected by individual countries, they often migrate through unregulated waters and are at increased risk. The IUCN designated M. birostris as “Vulnerable with increased risk of extinction” in November 2011. In the same year, M. alfredi was also classified as Vulnerable with local populations of less than 1000 individuals and little or no exchange between subgroups.
In addition to these international initiatives, some countries are taking their own actions. New Zealand has banned the capture of sea devils since 1953. In June 1995, the Maldives banned the export of all species of rays and their body parts, effectively ending manta catching and tightening controls in 2009. In the Philippines, manta catching was banned in 1998, but canceled in 1999 under pressure from local fishermen. After a survey of fish stocks in 2002, the ban was reintroduced.
The sea devil is protected, hunting in Mexican waters was banned back in 2007. However, this ban is not always respected. Tougher laws apply on Albox Island off the Yucatan Peninsula, where sea devils are used to attract tourists. In 2009, Hawaii became the first in the US to ban manta killing. In 2010, a law was passed in Ecuador prohibiting all types of fishing for these and other skates.