Roughtail stingray
Encyclopedia
The roughtail stingray (Dasyatis centroura) is a species
of stingray
in the family
Dasyatidae, with separate populations in coastal waters of the northwestern, eastern, and southwestern Atlantic Ocean
. This bottom-dwelling species typically inhabits sandy or muddy areas with patches of invertebrate
cover, at a depth of 15–50 m (49.2–164 ft). It is seasonally migratory
, overwintering in offshore waters and moving into coastal habitat
s for summer. The largest stingray in the Atlantic, the roughtail stingray grows up to 2.6 m (8.5 ft) across and 300 kg (661.4 lb) in weight. It is plain in color, with an angular, diamond-shaped pectoral fin disc and a long, whip-tail tail bearing a subtle fin fold underneath. The many thorns on its back and tail serve to distinguish it from other stingrays that share its range
.
Often found lying on the bottom buried in sediment, the roughtail stingray is a generalist
predator that feeds on a variety of benthic invertebrate
s and bony fishes. It is aplacental viviparous, with the embryo
s receiving nourishment initially from yolk, and later from histotroph ("uterine milk") produced by the mother. In the northwestern Atlantic, females bear an annual litter of 4–6 young in fall and early winter, after a gestation period of 9–11 months. By contrast, in the Mediterranean there is evidence that females bear two litters of 2–6 young per year after a gestation period of only four months. Rays in the northwestern Atlantic are also larger at birth and sexual maturity
than those from the Mediterranean. The venom
ous tail spine of the roughtail stingray is potentially dangerous to humans. The International Union for Conservation of Nature (IUCN) has listed this species under Least Concern
overall and in the northwestern Atlantic, where it is not commercially utilized. However, in the Mediterranean and southwestern Atlantic it is subject to heavy fishing pressure and has been assessed as Near Threatened
.
Samuel Mitchell in one of the earliest North America
n works on ichthyology
, a short treatise on the fishes of New York
in the 1815 first volume of Transactions of the Literary and Philosophical Society of New York. Mitchell based his account on specimens caught off Long Island
, though did not designate any types, and named the new species Raja centroura, from the Greek
centoro ("pricker") in reference to its thorns. Subsequent authors moved this species to the genus Dasyatis. This ray may also be referred to as rough-tailed stingray, rough-tailed northern stingray, or thorny stingray.
The taxonomy
of the roughtail stingray is not fully resolved, with the disjunct
northwestern Atlantic, southwestern Atlantic, and eastern Atlantic populations differing in life history and perhaps representing a complex
of different species. Lisa Rosenberger's 2001 phylogenetic analysis of 14 Dasyatis species, based on morphology
, found that the roughtail stingray is the sister species to the broad stingray (D. lata), and that they form a clade
with the southern stingray
(D. americana) and the longtail stingray
(D. longa). The close relationship between the roughtail and southern stingrays was upheld by a genetic analysis published by Leticia de Almeida Leao Vaz and colleagues in 2006. The roughtail and broad stingrays are found in the Atlantic and Pacific Oceans respectively, and therefore likely diverged
before or with the formation of the Isthmus of Panama
(c. 3 Ma).
The roughtail stingray is broadly but discontinuously distributed in the coastal waters of the Atlantic Ocean. In the western Atlantic, it occurs from the Georges Bank
off New England
southward to Florida
, the Bahamas, and the northeastern Gulf of Mexico
; there are also scattered reports from Venezuela
to Argentina
. In the eastern Atlantic, it occurs from the southern Bay of Biscay
to Angola
, including the Mediterranean Sea
, Madeira
, and the Canary Islands
. A single record from Quilon
, India
was likely a misidentification.
One of the deepest-diving stingrays, the roughtail stingray has been recorded to a depth of 274 m (899 ft) in the Bahamas and regularly occurs down to 200 m (656.2 ft) in the Mediterranean. However, it is most common at a depth of 15–50 m (49.2–164 ft). This bottom-dwelling species favors live-bottom habitat (patches of rough terrain that are densely encrusted by sessile
invertebrate
s), and also frequents adjacent open areas of sand or mud. Rays in the northwestern Atlantic do not usually enter brackish water
, whereas those off West Africa
have been recorded from the lower reaches of large rivers.
The favored temperature range of the roughtail stingray is 15–22 °C (59–71.6 F), which is the most important factor determining its distribution. It conducts seasonal migrations
off the eastern United States
: from December to May, this ray is found over the middle and outer parts of the continental shelf
from Cape Hatteras
in North Carolina
to Florida, with larger rays occurring further south than smaller ones. In the spring, the population moves north of the Cape and towards the coast into bay
s, inlet
s, and saltier estuaries, though preserving the north-south gradient of body sizes. A similar migration, from shallow coastal waters in summer to deeper offshore waters in winter, apparently occurs in the Mediterranean. Pregnant females tend to be found apart from other individuals.
The roughtail stingray has a diamond-shaped pectoral fin disk 1.2–1.3 times as wide as long, with straight to gently sinuous margins, rather angular outer corners, and a moderately long, obtuse snout. The eyes are proportionally smaller than other stingrays in its range and immediately followed by larger spiracle
s. There is a curtain of skin between the nostril
s with a finely fringed posterior margin. The mouth is bow-shaped with a row of six papillae (nipple-like structures) across the floor. The seven upper and 12–14 lower tooth rows at the center are functional, though the total number of tooth rows is much greater. The teeth are arranged with a quincunx
pattern into flattened surfaces; each has a tetragonal base with a blunt crown in juveniles and females, and a pointed cusp in adult males.
The pelvic fins have nearly straight margins and angular tips. The tail is long and whip-like, measuring some 2.5 times the length of the disc. A long, saw-toothed spine is placed atop the tail at around half a disc length back from the tail base; sometimes one or two replacement spines are also present in front of the existing one. Behind the spine, there is a long ventral fin fold that is much lower than that of the southern stingray. Individuals under 46–48 cm (18.1–18.9 in) across have completely smooth skin. Larger rays develop increasing numbers of distinctive tubercle
s or bucklers (flat-based thorns) over the middle of the back from the snout to the tail base, as well as dorsal and lateral rows of thorns on the tail. The bucklers vary in size, with the largest of equal diameter to the eye, and may bear up to three thorns each. This species is a uniform dark brown or olive above, and off-white below without dark fin margins. Among the largest members of its family, the roughtail stingray can reach 2.6 m (8.5 ft) across, 4 m (13.1 ft) long, and 300 kg (661.4 lb) in weight. Females grow larger than males.
predator whose diet generally reflects the most available prey in its environment. It mainly captures prey off the bottom, but also opportunistically takes free-swimming prey. A variety of invertebrate
s, as well as bony fishes such as sand lance
and scup
, are known to be consumed. Off Massachusetts
, the main prey are crab
s (Cancer
), bivalves (Mya
), gastropods (Polinices
), squid
(Loligo
) and annelid worms. In Delaware Bay
, most of its diet consists of the shrimp
Cragon septemspinosa and the blood worm Glycera dibranchiata; the overall dietary composition there is nearly identical to that of bluntnose stingray
s (D. say) that share the bay. The shrimp Upogebia affinis is a major food source off Virginia
. Off Florida, crustacean
s (Rananoides, Ovalipes
, Sicyonia brevirostris
, and Portunus
) and polychaete worms are the most important prey.
Shark
s and other large fishes, in particular the great hammerhead
(Sphyrna mokarran), prey upon the roughtail stingray. The live sharksucker (Echeneis naucrates) is sometimes found attached to its body. Known parasites of this species include the tapeworms Acanthobothrium woodsholei, Anthocephalum centrurum, Lecanicephalum sp., Oncomegas wageneri, Polypocephalus sp., Pterobothrium senegalense, and Rhinebothrium maccallumi, the monogenea
n Dendromonocotyle centrourae, and the leech
Branchellion torpedinis.
Like other stingrays, the roughtail stingray is aplacental viviparous: the developing embryo
is initially sustained by yolk and later by histotroph ("uterine milk", containing protein
s, lipid
s, and mucus
) delivered by the mother through finger-like projections of the uterine
epithelium
called "trophonemata". Only the left ovary
and uterus
are functional in adult females. Off the eastern United States, reproduction occurs on an annual cycle with mating in winter and early spring. After a gestation period
of 9–11 months, females give birth to 4–6 (typically five) young in fall or early winter. The newborns measure 34–37 cm (13.4–14.6 in) across. Off North Africa
, birthing occurs in June and December, indicating either that females bear two litters per year with a four-month gestation period, or that there are two cohorts of females bearing one litter per year with a ten-month gestation period. The newborns are much smaller than those in the northwestern Atlantic at 8–13 cm (3.1–5.1 in) across, which would be consistent with a shorter gestation period. The size at maturity also differs between the two regions: off the eastern United States males and females mature at 130–150 cm (51.2–59.1 in) and 140–160 cm (55.1–63 in) across respectively, while off North Africa males and females mature at 80 cm (31.5 in) and 66–100 cm (26–39.4 in) across respectively.
ous spine, the roughtail stingray can inflict a severe wound and can be very dangerous for fishers to handle. However, it is not aggressive and usually occurs too deep to be encountered by beachgoers. It has been reported to damage farmed shellfish
beds. The pectoral fins or "wings" are sold for human consumption fresh, smoked, or dried and salted
; the rest of the ray may also be processed to obtain fishmeal and liver oil
. The International Union for Conservation of Nature (IUCN) has assessed the roughtail stingray as of Least Concern
worldwide, while noting that as a large, slow-reproducing species it is susceptible to population depletion.
In the northwestern Atlantic, the roughtail stingray is listed under Least Concern; it is not targeted or utilized by commercial fisheries, though inconsequential numbers are captured incidentally
in trawls and on demersal longlines. Historically, it was sometimes ground up for fertilizer
. In the Mediterranean, intensive fishing occurs in the habitat of the roughtail stingray, and it is caught incidentally by artisanal
and commercial fishers using trawls, longlines, gillnet
s, and handlines. Though no specific data is available on this species, declines of other species and its intrinsic susceptibility to depletion have led it to be assessed as Near Threatened
in the region. In the southwestern Atlantic, the roughtail stingray and other large rays are heavily fished using demersal trawls, gillnets, longlines, and hook-and-line; this fishing pressure is liable to increase due to growing commercial interest in using large stingrays for minced fish products. Anecdotal reports suggest that landings of this species are decreasing, leading to a regional assessment of Near Threatened.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of stingray
Myliobatiformes
Myliobatiformes is one of the four orders of batoids, cartilaginous fishes related to sharks. They were formerly included in the order Rajiformes, but more recent phylogenetic studies have shown that the myliobatiforms are a monophyletic group, and that its more derived members evolved their...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Dasyatidae, with separate populations in coastal waters of the northwestern, eastern, and southwestern Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. This bottom-dwelling species typically inhabits sandy or muddy areas with patches of invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
cover, at a depth of 15–50 m (49.2–164 ft). It is seasonally migratory
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
, overwintering in offshore waters and moving into coastal habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s for summer. The largest stingray in the Atlantic, the roughtail stingray grows up to 2.6 m (8.5 ft) across and 300 kg (661.4 lb) in weight. It is plain in color, with an angular, diamond-shaped pectoral fin disc and a long, whip-tail tail bearing a subtle fin fold underneath. The many thorns on its back and tail serve to distinguish it from other stingrays that share its range
Range (biology)
In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...
.
Often found lying on the bottom buried in sediment, the roughtail stingray is a generalist
Generalist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources . A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either...
predator that feeds on a variety of benthic invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s and bony fishes. It is aplacental viviparous, with the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
s receiving nourishment initially from yolk, and later from histotroph ("uterine milk") produced by the mother. In the northwestern Atlantic, females bear an annual litter of 4–6 young in fall and early winter, after a gestation period of 9–11 months. By contrast, in the Mediterranean there is evidence that females bear two litters of 2–6 young per year after a gestation period of only four months. Rays in the northwestern Atlantic are also larger at birth and sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
than those from the Mediterranean. The venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
ous tail spine of the roughtail stingray is potentially dangerous to humans. The International Union for Conservation of Nature (IUCN) has listed this species under Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
overall and in the northwestern Atlantic, where it is not commercially utilized. However, in the Mediterranean and southwestern Atlantic it is subject to heavy fishing pressure and has been assessed as Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
.
Taxonomy and phylogeny
The first description of the roughtail stingray was published by American naturalistNaturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Samuel Mitchell in one of the earliest North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n works on ichthyology
Ichthyology
Ichthyology is the branch of zoology devoted to the study of fish. This includes skeletal fish , cartilaginous fish , and jawless fish...
, a short treatise on the fishes of New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
in the 1815 first volume of Transactions of the Literary and Philosophical Society of New York. Mitchell based his account on specimens caught off Long Island
Long Island
Long Island is an island located in the southeast part of the U.S. state of New York, just east of Manhattan. Stretching northeast into the Atlantic Ocean, Long Island contains four counties, two of which are boroughs of New York City , and two of which are mainly suburban...
, though did not designate any types, and named the new species Raja centroura, from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
centoro ("pricker") in reference to its thorns. Subsequent authors moved this species to the genus Dasyatis. This ray may also be referred to as rough-tailed stingray, rough-tailed northern stingray, or thorny stingray.
The taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
of the roughtail stingray is not fully resolved, with the disjunct
Disjunct distribution
In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but widely separated from each other geographically...
northwestern Atlantic, southwestern Atlantic, and eastern Atlantic populations differing in life history and perhaps representing a complex
Species complex
A species complex is a group of closely related species, where the exact demarcation between species is often unclear or cryptic owing to their recent and usually still incomplete reproductive isolation. Ring species, superspecies and cryptic species complex are example of species complex...
of different species. Lisa Rosenberger's 2001 phylogenetic analysis of 14 Dasyatis species, based on morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
, found that the roughtail stingray is the sister species to the broad stingray (D. lata), and that they form a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
with the southern stingray
Southern stingray
The southern stingray, Dasyatis americana, is a stingray of the family Dasyatidae found in tropical and subtropical waters of the Western Atlantic Ocean from New Jersey to Brazil. It has a flat, diamond-shaped disc, with a mud brown, olive, and grey dorsal surface and white underbelly...
(D. americana) and the longtail stingray
Longtail stingray
The longtail stingray , is a species of stingray in the family Dasyatidae, found in the eastern Pacific Ocean from Baja California to Colombia. It inhabits sandy habitats down to a depth of...
(D. longa). The close relationship between the roughtail and southern stingrays was upheld by a genetic analysis published by Leticia de Almeida Leao Vaz and colleagues in 2006. The roughtail and broad stingrays are found in the Atlantic and Pacific Oceans respectively, and therefore likely diverged
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
before or with the formation of the Isthmus of Panama
Isthmus of Panama
The Isthmus of Panama, also historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It contains the country of Panama and the Panama Canal...
(c. 3 Ma).
Distribution and habitat
Georges Bank
Georges Bank is a large elevated area of the sea floor which separates the Gulf of Maine from the Atlantic Ocean and is situated between Cape Cod, Massachusetts and Cape Sable Island, Nova Scotia ....
off New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
southward to Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
, the Bahamas, and the northeastern Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
; there are also scattered reports from Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
to Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. In the eastern Atlantic, it occurs from the southern Bay of Biscay
Bay of Biscay
The Bay of Biscay is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Brest south to the Spanish border, and the northern coast of Spain west to Cape Ortegal, and is named in English after the province of Biscay, in the Spanish...
to Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
, including the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
, Madeira
Madeira
Madeira is a Portuguese archipelago that lies between and , just under 400 km north of Tenerife, Canary Islands, in the north Atlantic Ocean and an outermost region of the European Union...
, and the Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
. A single record from Quilon
Quilon
Quilon may refer to,* Venad, a former state on Malabar Coast, India* Kollam , Kerala state, India* Kollam district, Kerala state...
, India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
was likely a misidentification.
One of the deepest-diving stingrays, the roughtail stingray has been recorded to a depth of 274 m (899 ft) in the Bahamas and regularly occurs down to 200 m (656.2 ft) in the Mediterranean. However, it is most common at a depth of 15–50 m (49.2–164 ft). This bottom-dwelling species favors live-bottom habitat (patches of rough terrain that are densely encrusted by sessile
Sessility (zoology)
In zoology, sessility is a characteristic of animals which are not able to move about. They are usually permanently attached to a solid substrate of some kind, such as a part of a plant or dead tree trunk, a rock, or the hull of a ship in the case of barnacles. Corals lay down their own...
invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s), and also frequents adjacent open areas of sand or mud. Rays in the northwestern Atlantic do not usually enter brackish water
Brackish water
Brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root "brak," meaning "salty"...
, whereas those off West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
have been recorded from the lower reaches of large rivers.
The favored temperature range of the roughtail stingray is 15–22 °C (59–71.6 F), which is the most important factor determining its distribution. It conducts seasonal migrations
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
off the eastern United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
: from December to May, this ray is found over the middle and outer parts of the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
from Cape Hatteras
Cape Hatteras
Cape Hatteras is a cape on the coast of North Carolina. It is the point that protrudes the farthest to the southeast along the northeast-to-southwest line of the Atlantic coast of North America...
in North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
to Florida, with larger rays occurring further south than smaller ones. In the spring, the population moves north of the Cape and towards the coast into bay
Bay
A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...
s, inlet
Inlet
An inlet is a narrow body of water between islands or leading inland from a larger body of water, often leading to an enclosed body of water, such as a sound, bay, lagoon or marsh. In sea coasts an inlet usually refers to the actual connection between a bay and the ocean and is often called an...
s, and saltier estuaries, though preserving the north-south gradient of body sizes. A similar migration, from shallow coastal waters in summer to deeper offshore waters in winter, apparently occurs in the Mediterranean. Pregnant females tend to be found apart from other individuals.
Description
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...
s. There is a curtain of skin between the nostril
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s with a finely fringed posterior margin. The mouth is bow-shaped with a row of six papillae (nipple-like structures) across the floor. The seven upper and 12–14 lower tooth rows at the center are functional, though the total number of tooth rows is much greater. The teeth are arranged with a quincunx
Quincunx
A quincunx is a geometric pattern consisting of five points arranged in a cross, that is five coplanar points, four of them forming a square or rectangle and a fifth at its center...
pattern into flattened surfaces; each has a tetragonal base with a blunt crown in juveniles and females, and a pointed cusp in adult males.
The pelvic fins have nearly straight margins and angular tips. The tail is long and whip-like, measuring some 2.5 times the length of the disc. A long, saw-toothed spine is placed atop the tail at around half a disc length back from the tail base; sometimes one or two replacement spines are also present in front of the existing one. Behind the spine, there is a long ventral fin fold that is much lower than that of the southern stingray. Individuals under 46–48 cm (18.1–18.9 in) across have completely smooth skin. Larger rays develop increasing numbers of distinctive tubercle
Tubercle
A tubercle is generally a wart-like projection, but it has slightly different meaning depending on which family of plants or animals it is used to refer to....
s or bucklers (flat-based thorns) over the middle of the back from the snout to the tail base, as well as dorsal and lateral rows of thorns on the tail. The bucklers vary in size, with the largest of equal diameter to the eye, and may bear up to three thorns each. This species is a uniform dark brown or olive above, and off-white below without dark fin margins. Among the largest members of its family, the roughtail stingray can reach 2.6 m (8.5 ft) across, 4 m (13.1 ft) long, and 300 kg (661.4 lb) in weight. Females grow larger than males.
Biology and ecology
The roughtail stingray is reportedly not highly active, spending much time buried in the sediment. It is a generalistGeneralist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources . A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either...
predator whose diet generally reflects the most available prey in its environment. It mainly captures prey off the bottom, but also opportunistically takes free-swimming prey. A variety of invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s, as well as bony fishes such as sand lance
Sand lance
A sand lance or sandlance is a fish belonging to the family Ammodytidae. Several species of sand lance are commonly known as "sand eels" or "sandeels", though they are not related to true eels. Another variant name is launce, and all names of the fish are references to its slender body and...
and scup
Scup
The scup, Stenotomus chrysops, is a fish which occurs primarily in the Atlantic from Massachusetts to South Carolina. Along with many other fish of the family Sparidae, it is also commonly known as porgy....
, are known to be consumed. Off Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
, the main prey are crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s (Cancer
Cancer (genus)
Cancer is a genus of marine crabs in the family Cancridae. It includes 8 extant species and 3 extinct species, including familiar crabs of the littoral zone, such as the European edible crab , the Jonah crab and the red rock crab...
), bivalves (Mya
Mya (genus)
Mya is a genus of bivalve molluscs, including seven species:*Mya arenaria Linnaeus, 1758*Mya baxteri Coan & Scott, 1997*Mya eideri Hopner Petersen, 1999*Mya neoovata Hopner Petersen, 1999*Mya neouddevallensis Hopner Petersen, 1999...
), gastropods (Polinices
Polinices
Polinices is a genus of sea snails, marine gastropod molluscs in the family Naticidae known as moon shells. Glossaulax Pilsbry, 1929 is a synonym or a subgenus of Polinices.-Species:Species within the genus Polinices include:...
), squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
(Loligo
Loligo
Loligo is a genus of squids and one of the most representative and widely distributed groups of myopsid squids.The genus was first described by Jean Baptiste Lamarck in 1798. However, the name had been used earlier than Lamarck and might even have been used by Pliny...
) and annelid worms. In Delaware Bay
Delaware Bay
Delaware Bay is a major estuary outlet of the Delaware River on the Northeast seaboard of the United States whose fresh water mixes for many miles with the waters of the Atlantic Ocean. It is in area. The bay is bordered by the State of New Jersey and the State of Delaware...
, most of its diet consists of the shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
Cragon septemspinosa and the blood worm Glycera dibranchiata; the overall dietary composition there is nearly identical to that of bluntnose stingray
Bluntnose stingray
The bluntnose stingray or Say's stingray is a species of stingray in the family Dasyatidae, native to the coastal waters of the western Atlantic Ocean from the U.S. state of Massachusetts to Venezuela. It is a bottom-dwelling species that prefers sandy or muddy habitats deep, and is migratory in...
s (D. say) that share the bay. The shrimp Upogebia affinis is a major food source off Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
. Off Florida, crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s (Rananoides, Ovalipes
Ovalipes
Ovalipes is a genus of crabs in the family Portunidae, containing 11 extant species:*Ovalipes australiensis Stephenson & Rees, 1968*Ovalipes catharus *Ovalipes elongatus Stephenson & Rees, 1968...
, Sicyonia brevirostris
Sicyonia brevirostris
Sicyonia brevirostris, the brown rock shrimp, is a species of prawn. It is found along the coasts of the western Atlantic Ocean and Gulf of Mexico from Norfolk, Virginia to Yucatán, including Cuba and the Bahamas....
, and Portunus
Portunus
Portunus is a genus of crab which includes several important species for fisheries, such as the blue swimming crab, Portunus pelagicus and the Gazami crab, P. trituberculatus . The genus Portunus contains more than 90 extant species and over 40 further species known only from fossils ....
) and polychaete worms are the most important prey.
Shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
s and other large fishes, in particular the great hammerhead
Great hammerhead
The great hammerhead is the largest species of hammerhead shark, family Sphyrnidae, attaining a maximum length of 6.1 m . It is found in tropical and warm temperate waters worldwide, inhabiting coastal areas and the continental shelf...
(Sphyrna mokarran), prey upon the roughtail stingray. The live sharksucker (Echeneis naucrates) is sometimes found attached to its body. Known parasites of this species include the tapeworms Acanthobothrium woodsholei, Anthocephalum centrurum, Lecanicephalum sp., Oncomegas wageneri, Polypocephalus sp., Pterobothrium senegalense, and Rhinebothrium maccallumi, the monogenea
Monogenea
Monogenea are a group of largely ectoparasitic members of the flatworm phylum Platyhelminthes, class Monogenea.-Characteristics:Monogenea are very small parasitic flatworms mainly found on skin or gills of fish....
n Dendromonocotyle centrourae, and the leech
Leech
Leeches are segmented worms that belong to the phylum Annelida and comprise the subclass Hirudinea. Like other oligochaetes such as earthworms, leeches share a clitellum and are hermaphrodites. Nevertheless, they differ from other oligochaetes in significant ways...
Branchellion torpedinis.
Like other stingrays, the roughtail stingray is aplacental viviparous: the developing embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
is initially sustained by yolk and later by histotroph ("uterine milk", containing protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s, lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
s, and mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
) delivered by the mother through finger-like projections of the uterine
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
epithelium
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...
called "trophonemata". Only the left ovary
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
and uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
are functional in adult females. Off the eastern United States, reproduction occurs on an annual cycle with mating in winter and early spring. After a gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
of 9–11 months, females give birth to 4–6 (typically five) young in fall or early winter. The newborns measure 34–37 cm (13.4–14.6 in) across. Off North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
, birthing occurs in June and December, indicating either that females bear two litters per year with a four-month gestation period, or that there are two cohorts of females bearing one litter per year with a ten-month gestation period. The newborns are much smaller than those in the northwestern Atlantic at 8–13 cm (3.1–5.1 in) across, which would be consistent with a shorter gestation period. The size at maturity also differs between the two regions: off the eastern United States males and females mature at 130–150 cm (51.2–59.1 in) and 140–160 cm (55.1–63 in) across respectively, while off North Africa males and females mature at 80 cm (31.5 in) and 66–100 cm (26–39.4 in) across respectively.
Human interactions
With its large size and long, venomVenom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
ous spine, the roughtail stingray can inflict a severe wound and can be very dangerous for fishers to handle. However, it is not aggressive and usually occurs too deep to be encountered by beachgoers. It has been reported to damage farmed shellfish
Aquaculture
Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...
beds. The pectoral fins or "wings" are sold for human consumption fresh, smoked, or dried and salted
Salting (food)
Salting is the preservation of food with dry edible salt. It is related to pickling . It is one of the oldest methods of preserving food, and two historically significant salt-cured foods are dried and salted cod and salt-cured meat.Salting is used because most bacteria, fungi and other potentially...
; the rest of the ray may also be processed to obtain fishmeal and liver oil
Shark liver oil
Shark liver oil is obtained from sharks that are caught for food purposes and are living in cold, deep oceans. The liver oil from sharks has been used by fishermen for centuries as a folk remedy for general health...
. The International Union for Conservation of Nature (IUCN) has assessed the roughtail stingray as of Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
worldwide, while noting that as a large, slow-reproducing species it is susceptible to population depletion.
In the northwestern Atlantic, the roughtail stingray is listed under Least Concern; it is not targeted or utilized by commercial fisheries, though inconsequential numbers are captured incidentally
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
in trawls and on demersal longlines. Historically, it was sometimes ground up for fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
. In the Mediterranean, intensive fishing occurs in the habitat of the roughtail stingray, and it is caught incidentally by artisanal
Artisan fishing
Artisan fishing is a term used to describe small scale low-technology commercial or subsistence fishing practices. The term particularly applies to coastal or island ethnic groups using traditional techniques such as rod and tackle, arrows and harpoons, throw nets and drag nets, and traditional...
and commercial fishers using trawls, longlines, gillnet
Gillnet
Gillnetting is a common fishing method used by commercial and artisanal fishermen of all the oceans and in some freshwater and estuary areas. The gillnet also is used by fisheries scientists to monitor fish populations. Because gillnets can be so effective their use is closely monitored and...
s, and handlines. Though no specific data is available on this species, declines of other species and its intrinsic susceptibility to depletion have led it to be assessed as Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
in the region. In the southwestern Atlantic, the roughtail stingray and other large rays are heavily fished using demersal trawls, gillnets, longlines, and hook-and-line; this fishing pressure is liable to increase due to growing commercial interest in using large stingrays for minced fish products. Anecdotal reports suggest that landings of this species are decreasing, leading to a regional assessment of Near Threatened.