| Atlantic stingray | |
|---|---|
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Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Order: | Myliobatiformes |
| Family: | Dasyatidae |
| Genus: | Hypanus |
| Species: | H. sabinus |
| Binomial name | |
| Hypanus sabinus (Lesueur, 1824) | |
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| Range of the Atlantic stingray | |
| Synonyms[2] | |
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TheAtlantic stingray (Hypanus sabinus) is aspecies ofstingray in thefamilyDasyatidae, common along theAtlantic coast ofNorth America fromChesapeake Bay toMexico, includingbrackish andfreshwaterhabitats. It may be distinguished from other stingrays in the area by its relatively elongated snout.[3] This species is of littlecommercial importance,[4] other than for sale in theaquarium industry.
The Atlantic stingray was described by FrenchnaturalistCharles Alexandre Lesueur asTrygon sabina, in an 1824 volume of theJournal of the Academy of Natural Sciences of Philadelphia. He based his account on a damaged male specimen collected by American naturalistTitian Ramsay Peale during theAcademy's 1817 expedition toFlorida.[5] Since then, various authors have included this species in the obsolete generaPastinaca,Dasybatus (or the variantsDasibatis andDasybatis), andAmphotistius, all of which were eventuallysynonymized with the genusDasyatis.[6]
A 2001 phylogenetic analysis by Lisa Rosenberger, based onmorphology, found that the Atlantic stingray is one of the morebasal members of itsgenus. It is theoutgroup to a largeclade that contains, amongst others, thesouthern stingray (H. americana), theroughtail stingray (Bathytoshia centroura), thelongnose stingray (H. guttata), and thepearl stingray (Fontitrygon margaritella).[7]
The Atlantic Stingray is found in the westernAtlantic Ocean fromChesapeake Bay southward toFlorida and theGulf of Mexico, to as far asCampeche,Mexico.[1] Records of this species fromGrenada,Suriname, andBrazil are doubtful and may represent other species. The Atlantic stingray is capable of tolerating varyingsalinities and can enterfreshwater; it has been reported from theMississippi River,Lake Pontchartrain, and theSt. Johns River inFlorida.[8] The stingrays in the St. Johns River system represent the only permanent freshwaterelasmobranch population in North America.[3][9][10]
This species inhabits shallow coastal waters over sandy or silty bottoms,estuaries, andlakes. They prefer water temperatures over 15 °C (59 °F) and can tolerate temperatures over 30 °C (86 °F). These stingrays conduct seasonal migrations to stay in warmer water: they are only present in the northerly Chesapeake bay in the summer and fall, and elsewhere they migrate to deeper water in the winter. When inshore, they usually stay at depths of 2–6 m (6.6–19.7 ft), and after migrating offshore they may be found as deep as 25 m (82 ft).[3]
One of the smallest stingray species, the Atlantic stingray attains a maximum length of 61 cm (24 in) and a weight of 4.9 kg (11 lb).[4] It has a spade-shapedpectoral fin disk 1.1 times as wide as long, with rounded corners and concave anterior margins. Thesnout is relatively long. There are three stoutpapillae on the floor of the mouth; theteeth are rounded, with a flat, blunt surface. During the reproductive season, the teeth of mature males change to feature long, sharp cusps that curve towards the corners of the mouth, for gripping onto females during mating. Thetail is long and whip-like, with a serrated spine measuring a quarter of the width of the disk. The spine is replaced annually between June and October. Dorsal and ventral fin folds are present on the tail.[3][8]
Larger Atlantic stingrays develop tubercles or thorns along the midline of the back to the origin of the tail spine. Some larger females also develop tubercles around theeyes andspiracles. The coloration is brown or yellowish brown above, becoming lighter towards the margin of the disk and sometimes with a dark stripe along the midline, and white or light gray below. The tail fin folds are yellowish. In larger individuals the tail may be flecked with gray near the base and completely dark towards the tip.[3][8]
The Atlantic stingray feeds mostly onbenthicinvertebrates such asbivalves,tube anemones,amphipods,crustaceans, andnereid worms, which they locate using theirelectroreceptiveampullae of Lorenzini. The exact composition of their diet varies by geographical location. When feeding, these rays will position themselves facing the current so that the sediment will be washed away.[11] Numerous species ofsharks, such as thetiger shark (Galeocerdo cuvier) and thebull shark (Carcharhinas leucas), are major predators of the Atlantic stingray. In freshwater habitats, they may be preyed upon byAmerican alligators (Alligator mississippiensis). A knownparasite of freshwater Atlantic stingrays isArgulus, afish louse that feeds on skinmucus.[3]
Despite having a regular freshwater presence, the Atlantic stingray is physiologicallyeuryhaline and no population has evolved the specializedosmoregulatory mechanisms found in theriver stingrays of the familyPotamotrygonidae. This may be due to the relatively recent date of freshwater colonization (under one million years), and/or possibly incomplete genetic isolation of the freshwater populations, as they remain capable of surviving insalt water. Freshwater Atlantic stingrays have only 30–50% the concentration ofurea and otherosmolytes in their blood compared to marine populations. However, theosmotic pressure between their internal fluids and external environment still causes water todiffuse into their bodies, and they must produce large quantities of diluteurine (at 10 times the rate of marine individuals) to compensate.[9]
Like other stingrays, the Atlantic stingray isviviparous. Both marine and freshwater populations inFlorida have an annual mating season from September or October to April, thoughovulation does not occur until late March or early April. Courtship involves the male following the female and biting at her body and fins, and the male will grip onto the female's pectoral fin to assist incopulation. Theembryos are sustained by ayolk sac until around day 60, after which they are nourished by uterine milk secreted by the mother (histotrophy). Litters of 1–4 young are born from late July to early August, after agestation period of 4–4.5 months. Newborns measure 10–13 centimetres (3.9–5.1 in) wide. Marine males mature at a disk width of 20 cm (7.9 in) and females at a disk width of 24 cm (9.4 in). Freshwater males mature at a disk width of 21 cm (8.3 in) and females at a disk width of 22 cm (8.7 in).[3][12]
If stepped on, the Atlantic stingray can inflict a painful, though rarely life-threatening wound. Large numbers of Atlantic stingrays are caught asbycatch ingillnets targetingflounder offNorth Carolina, but most are released alive. They are also caught as bycatch in small numbers in recreational and commercialtrout gillnets,sharkdrift nets, and nearshoretrawls. As there is nofishery targeting this species and bycatch mortality appears to be low, it was assessed as ofLeast Concern by theWorld Conservation Union.[1] However, some localized freshwater populations have shown reduced health and reproduction due to declining water quality.[3]
