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| Spotted eagle ray | |
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| Spotted eagle ray atTurks and Caicos | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Order: | Myliobatiformes |
| Family: | Aetobatidae |
| Genus: | Aetobatus |
| Species: | A. narinari |
| Binomial name | |
| Aetobatus narinari | |
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| Range of spotted eagle ray as traditionally recognized, but seetext | |
| Synonyms[2] | |
Aetobatis latirostris | |
Thespotted eagle ray (Aetobatus narinari) is acartilaginous fish of theeagle ray family, Aetobatidae. As traditionally recognized, it is found globally in tropical regions, including theAtlantic,Pacific andIndian Oceans. Recent authorities have restricted it to the Atlantic (including theCaribbean andGulf of Mexico) with other populations recognized as theocellated eagle ray (A. ocellatus) andPacific white-spotted eagle ray (A. laticeps). Spotted eagle rays are most commonly seen alone, but occasionally swim in groups. They areovoviviparous, the female retaining the eggs then releasing the young as miniature versions of the parent.
This ray can be identified by its darkdorsal surface covered in white spots or rings. Near the base of the ray's relatively long tail, just behind thepelvic fins, are severalvenomous, barbed stingers. Spotted eagle rays commonly feed on small fish andcrustaceans, and will sometimes dig with their snouts to look for food buried in the sand of the sea bed. These rays are commonly observed leaping out of the water, and on at least two occasions have been reported as having jumped into boats, in one incident resulting in the death of a woman in theFlorida Keys. The spotted eagle ray is hunted by a wide variety of sharks. The rays are considerednear threatened on theIUCN Red List. They are fished mainly in Southeast Asia and Africa, the most common market being in commercial trade and aquariums. They are protected in theGreat Barrier Reef.
The spotted eagle ray was first described by Swedish botanistBengt Anders Euphrasén asRaja narinari in 1790 from a specimen collected at an unknown location (possibly the coast of Brazil) during a trip he made to theAntilles, and was later classified asStoasodon narinari.[1][2][3] Its current genus name isAetobatus, derived from the Greek wordsaetos (eagle) andbatis (ray). The spotted eagle ray belongs to the Myliobatidae, which includes the well knownmanta ray. Most rays in the family Myliobatidae swim in the open ocean rather than close to the sea floor.[2]
Although traditionally considered to have a circumglobal distribution in tropical oceans throughout the world, recent authorities have restricted the trueAetobatus narinari to the Atlantic Ocean based ongenetic andmorphologic evidence.[4][5][6][7] TheIndo-Pacific population isAetobatus ocellatus and the East Pacific isAetobatus laticeps.[6][7]
The spotted eagle ray has many different common names, including white-spotted eagle ray, bonnet skate, bonnet ray, duckbill ray and spotted duck-billed ray.[8][9][10]
Spotted eagle rays have flat disk-shaped bodies, deep blue or black with white spots on top with a white underbelly, and distinctive flat snouts similar to a duck's bill.[11] Their tails are longer than other rays and may have 2–6 venomous spines, behind the pelvic fins. The front of the wing-likepectoral disk has five small gills in its underside.[12]
Mature spotted eagle rays can be up to 5 meters (16 ft) in length; the largest spotted eagle rays have a wingspan of up to 3 meters (10 ft) and a mass of 230 kilograms (507 lb).[13][14]
One male, or sometimes several, will pursue a female. When one of the males approaches the female, he uses his upper jaw to grab herdorsum. The male will then roll the female over by grabbing one of herpectoral fins, which are located on either side of her body. Once he is on herventral side, the male puts aclasper into the female, connecting themventer to venter, with both undersides together. The mating process lasts for 30–90 seconds.[2]
The spotted eagle ray developsovoviviparously; the eggs are retained in the female and hatch internally, feeding off ayolk sac until live birth.[2] After a gestation period of one year the mother ray will give birth to a maximum of four pups.[1] When the pups are first born, their discs measure from 17–35 centimeters (6.7–13.8 in) across.[2] The rays mature in 4 to 6 years.[1][15] Genetic evidence indicates that the spotted eagle ray can undergo consecutive parthenogenesis.[16]
Spotted eagle ray preys mainly uponbivalves, crabs,whelks and otherbenthicinfauna. They also feed onmollusks (such as thequeen conch)[17] and crustaceans, particularlymalacostracans,[18][19] as well as echinoderms,polychaete worms,[20] hermit crabs,[21]shrimp, octopuses, and some smallfish.[22]
The spotted eagle ray's specializedchevron-shaped tooth structure helps it to crush the mollusks' hard shells.[13][14] The jaws of these rays have developedcalcified struts to help them break through the shells of mollusks, by supporting the jaws and preventing dents from hard prey.[23] These rays have the unique behavior of digging with their snouts in the sand of the ocean.[24] While doing this, a cloud of sand surrounds the ray and sand spews from its gills. One study has shown that there are no differences in the feeding habits of males and females or in rays from different regions of Australia and Taiwan.[19]
Spotted eagle rays prefer to swim in waters of 24 to 27 °C (75 to 81 °F). Their daily movement is influenced by thetides; one tracking study showed that they are more active during high tides. Uniquely among rays they dig with their snouts in the sand,[24] surrounding themselves in a cloud of sand that spews from their gills. They also exhibit two motions in which theabdomen and thepectoral fins are moved rapidly up and down: the pelvic thrust and the extreme pelvic thrust. The pelvic thrust is usually performed by a solitary ray, and repeated four to five times rapidly. The extreme pelvic thrust is most commonly observed when the ray is swimming in a group, from which it will separate itself before vigorously thrusting with itspectoral fins. The rays also performs dips and jumps; in a dip the ray will dive and then come back up rapidly, perhaps as many as five times consecutively. There are two main types of jump: in one, the ray propels itself vertically out of the water, to which it returns along the same line; the other is when the ray leaps at a 45 degree angle, often repeated multiple times at high speeds. When in shallow waters or outside their normal swimming areas the rays are most commonly seen alone, but they do also congregate in schools. One form of travelling is called loose aggregation, which is when three to sixteen rays are swimming in a loose group, with occasional interactions between them. A school commonly consists of six or more rays swimming in the same direction at exactly the same speed.[25]
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The dorsal spots make the spotted eagle ray an aquarium attraction, although because of its large size it is likely kept only atpublic aquariums.[8] There are no target fisheries for the spotted eagle ray, but it is often eaten after being caught unintentionally asbycatch.[8] There have been several reported incidents of spotted eagle rays leaping out of the water onto boats and landing on people.[26][27] Nevertheless, spotted eagle rays do not pose a significant threat to humans, as they are shy and generally avoid human contact.[2] Interactions with an individual snorkeler in the Caribbean has been reported especially in Jamaica involving one, two and even three spotted eagle rays. The rays may exhibit a behavior similar to human curiosity which allows the snorkeler to observe the eagle ray who may slow down so as to share more time with the much slower human observer if the human observer appears to be unthreatening or interesting to the spotted eagle ray.
Spotted eagle rays, in common with many other rays, often fall victim to sharks such as thetiger shark, thelemon shark, thebull shark, thesilver tip shark, and thegreat hammerhead shark.[28][29] A great hammerhead shark has been observed attacking a spotted eagle ray in open water by taking a large bite out of one of itspectoral fins, thus incapacitating the ray. The shark then used its head to pin the ray to the bottom and pivoted to take the ray in its jaws, head first.[30] Sharks have also been observed to follow female rays during the birthing season, and feed on the newborn pups.[2]
As other rays, spotted eagle rays are host to a variety ofparasites. Internal parasites include thegnathostomatidnematodeEchinocephalus sinensis in thespiral intestine.[31] External parasites include themonocotylidmonogeneansDecacotyle octona,[32]Decacotyle elpora[32] andThaumatocotyle pseudodasybatis[32][33] on thegills.
As traditionally defined, spotted eagle rays are found globally in tropical regions from theIndo-Pacific region from the westernPacific Ocean, theIndian Ocean, and the westernAtlantic Ocean.[34]
They are found in shallow coastal water bycoral reefs and bays, in depths down to 80 meters (262 ft).[13]Spotted eagle rays are found in warm and temperate waters worldwide. In the westernAtlantic Ocean it is found off the eastern coast ofUnited States of America, theGulf Stream, theCaribbean, and down past the southern part ofBrazil. In theIndian Ocean, it is found from theRed Sea down toSouth Africa and eastward to theAndaman Sea. In the WesternPacific Ocean it can be found near Japan and north of Australia.[2] In the Central Pacific Ocean, it can be found throughout the Hawaiian Islands. In the Eastern-Pacific Ocean, it is found in theGulf of California down throughPuerto Pizarro, an area that includes theGalapagos Islands. Spotted eagle rays are most commonly seen in bays and reefs. They spend much of their time swimming freely in open waters, generally in schools close to the surface, and can travel long distances in a day.[2]
Within these regions, there are significant variations ingenetics andmorphology.[6][4][5] As a consequence, recent authorities have split it into three: This restricts the true spotted eagle ray (A. narinari) to the Atlantic, while theIndo-Pacific population is theocellated eagle ray (A. ocellatus) and the East Pacific is thePacific white-spotted eagle ray (A. laticeps).[6][7]
The spotted eagle ray is included in theIUCN's Red List as "near threatened". The rays are caught mainly in Southeast Asia and Africa. They are also common in commercial marine life trade and are displayed in aquariums. Among the many efforts to help protect this species, South Africa's decision to deploy fewer protectiveshark nets has reduced the number of deaths caused by entanglement. South Africa has also placed restrictions on the number of rays that can be bought per person per day. In the U.S. state of Florida, the fishing, landing, purchasing and trading of spotted eagle ray are outlawed. This ray is also protected in theGreat Barrier Reef on the eastern coast of Australia.[1]
In Europe there is a breeding program managed by theEAZA for spotted eagle rays to reduce the amount of wild caught individuals needed by public aquaria. From the start until 2018Burgers' Zoo in the Netherlands kept thestudbook. Since 2018,Wroclaw Zoo in Poland is the new studbook keeper. Burgers' Zoo was also the first place in Europe to breed with the species and in 2018 was the most successful breeder worldwide with over 55 births.[35][36][37]
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