Bluntnose stingray
Encyclopedia
The bluntnose stingray or Say's stingray (Dasyatis say, often misspelled sayi) 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 habitat
s 1–10 m (3.3–32.8 ft) deep, and is migratory
in the northern portion of its range. Typically growing to 78 cm (30.7 in) across, the bluntnose stingray is characterized by a rhomboid pectoral fin disc with broadly rounded outer corners and an obtuse-angled snout. It has a whip-like tail with both an upper keel and a lower fin fold, and a line of small tubercle
s along the middle of its back.
More active at night than during the day when it is usually buried in sediment, the bluntnose stingray is a predator of small benthic invertebrate
s and bony fishes. This species is aplacental viviparous, in which the unborn young are nourished initially by yolk, and later histotroph ("uterine milk") produced by their mother. Females give birth to 1–6 pups every May after a gestation period
of 11–12 months, most of which consists of a period of arrested embryonic development
. The venom
ous tail spine of the bluntnose stingray is potentially dangerous to unwary beachgoers. The International Union for Conservation of Nature (IUCN) has listed this species under Least Concern
, as it is widely distributed, common, and minimally threatened by commercial fisheries
.
Charles Alexandre Lesueur
originally described the bluntnose stingray from specimens collected in Little Egg Harbor
off the U.S. State
of New Jersey
. He published his account in an 1817 volume of the Journal of the Academy of Natural Sciences of Philadelphia, and named the new species Raja say in honor of Thomas Say
, one of the founding members of the Academy
. The species was moved to the genus Dasyatis by subsequent authors. In 1841, German biologists Johannes Peter Müller
and Friedrich Gustav Jakob Henle
erroneously gave the specific epithet as sayi in their Systematische Beschreibung der Plagiostomen, which thereafter became the typical spelling used in literature. Recently, there has been a push to use the correct original spelling again, though it has also been proposed that the International Commission on Zoological Nomenclature
(ICZN) officially emend the spelling to sayi, for consistency with previous usage.
Lisa Rosenberger's 2001 phylogenetic analysis, based on morphological
characters, found that the bluntnose stingray is one of the more basal members of its genus, and that it is a sister species to the diamond stingray
(D. dipterura) of the western Pacific Ocean
. The two species likely diverged
before or with the formation of the Isthmus of Panama
, some three million years ago.
, from Chesapeake Bay
southward through the Florida Keys
, the northern Gulf of Mexico
, and the Greater
and Lesser Antilles
; on rare occasions it is found as far north as New Jersey
and Massachusetts
, as far south as Venezuela
, and as far west as Mexico
. It is absent from the southern Gulf of Mexico and the Caribbean
coast of Central America
. Reports of this species from off Brazil
and Argentina
likely represent misidentifications of the groovebelly stingray
(D. hypostigma).
Common in coastal habitat
s such as bay
s, lagoon
s, and estuaries, the bluntnose stingray is a bottom-dwelling species usually found at a depth of 1–10 m (3.3–32.8 ft), though it has been recorded from as deep as 20 m (65.6 ft). It frequents sandy or muddy flats, preferring water with a salinity
of 25–43 ppt
and a temperature of 12–33 °C (53.6–91.4 F). Adult bluntnose stingrays are seldom found in seagrass
meadows or shoals, though the latter serves as a habitat for young rays. Along the U.S. East Coast, schools of bluntnose stingrays migrate
long distances northward into bays and estuaries to spend the summer, and move back to southern offshore waters for winter.
(D. sabina), which has a longer, more acute snout. The mouth is curved, with a central projection on the upper jaw that fits into an indentation on the lower jaw. There is a row of five papilla
e across the floor of the mouth, with the outermost pair smaller and set apart from the others. There are 36–50 upper tooth rows; the teeth have quadrangular bases and are arranged with a quincunx
pattern into flattened surfaces. The tooth crowns are rounded in females and juveniles, while those of males in breeding condition are triangular and pointed. The pelvic fins are triangular with rounded tips.
The whip-like tail measures over one and a half times as long as the disc and bears one or two long, serrated stinging spines on top, about a quarter of the tail length back from the base. The second spine, if present, is a replacement that periodically grows in front of the existing spine. Behind the spine, there are well-developed upper and lower fin folds, with the lower fold longer and wider than the upper. Small thorns or tubercles are found in a midline row from behind the eyes to the base of the tail spine, increasing in number with age. Adults also have prickles before and behind the eyes and on the outer parts of the disc. The dorsal coloration is grayish, reddish, or greenish brown; some individuals also possess bluish spots, are darker towards the sides and rear, or have a thin white disc margin. The ventral surface is whitish, sometimes with a dark disc margin or dark blotches. A record off French Guyana gives the maximum disc width of this species as 1 m (3.3 ft), but that specimen may have been misidentified and other sources give a maximum disc width of no more than 0.78 m (2.6 ft). Females grow larger than males.
. It has been known to follow the rising tide
to forage in water barely deep enough to cover its body. This species preys upon small invertebrate
s, including crustacean
s, annelid worms, and bivalve and gastropod molluscs, and bony fishes. It mainly targets benthic and burrowing organism
s, but also opportunistically takes free-swimming prey. In Delaware Bay
, this species feeds predominantly on the shrimp
Cragon septemspinosa and the blood worm Glycera dibranchiata, and its overall dietary composition is virtually identical to that of the roughtail stingray
(D. centroura), with which it shares the bay. The bluntnose stingray is preyed upon by larger fishes such as the bull shark
(Carcharhinus leucas). Known parasites of this species include the tapeworms Acanthobothrium brevissime and Kotorella pronosoma, the monogenea
n Listrocephalos corona, and the trematodes Monocotyle pricei and Multicalyx cristata.
Like other stingrays, the bluntnose stingray is aplacental viviparous. with the embryo
s initially sustained by yolk. Later in development, finger-like extensions of the uterine epithelium
called "trophonemata" surround the embryo and deliver protein
and lipid
-rich histotroph ("uterine milk") produced by the mother. Only the left ovary
and uterus
in adult females are functional. Mating occurs during a well-defined period from April to June, peaking in May, with the males presumably using their pointed teeth to grasp the females for copulation. However, embryonic development halts at the blastoderm
stage, shortly after the formation of the zygote
, and does not resume for approximately ten months. In the spring of the following year, the embryos rapidly mature over a period of 10–12 weeks. This period of embryonic diapause
may reflect the greater availability of food in the spring.
Including the extended period of diapause, the gestation period
lasts around 11–12 months, with 1–6 young being born in mid to late May. In 1941, in a shallow channel between Chincoteague Island and Cape Charles
, Virginia
, several large bluntnose stingrays were observed repeatedly breaking the surface and swimming rapidly in straight lines, some with their tails thrashing in the air; others were seen rising slowly to the surface and "hanging" for several minutes. One of the rays was hooked and the shock of capture caused it to release five near-term fetus
es, suggesting that this activity may have been related to parturition. The aborted young were pale with small yolk sac
s, and a swelling in the place of their tail spines. Females begin ovulating
a new batch of eggs immediately after giving birth, indicating that they have an annual reproductive cycle. Newborn rays measure 15–17 cm (5.9–6.7 in) across and weigh 170–250 g (6–8.8 oz). Males mature sexually
at disc width of 30–36 cm (11.8–14.2 in) and a weight of 3–6 kg (6.6–13.2 lb), while females mature at a disc width of 50–54 cm (19.7–21.3 in) and a weight of 7–15 kg (15.4–33.1 lb).
or rubber
footwear. The paralytic
venom
delivered may have potentially life-threatening effects on those with heart or respiratory problems, and is the subject of biomedical and neurobiological research. This species is popular with ecotourist
divers. Abundant and widespread, the bluntnose stingray is caught incidentally
by commercial
trawl and gillnet
fisheries operating in nearshore U.S. waters; these activities are not a threat to its population, as most captured rays are released alive. The impact of fishing in the southern parts of its range is uncertain, but is unlikely to significantly affect the species as a whole as these activities occur outside its centers of distribution. As a result, the International Union for Conservation of Nature has listed the bluntnose stingray as of Least Concern
.
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, native to the coastal waters of the western 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...
from the U.S. state
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...
of 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...
to 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...
. It is a bottom-dwelling species that prefers sandy or muddy 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 1–10 m (3.3–32.8 ft) deep, and is 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...
in the northern portion of its range. Typically growing to 78 cm (30.7 in) across, the bluntnose stingray is characterized by a rhomboid pectoral fin disc with broadly rounded outer corners and an obtuse-angled snout. It has a whip-like tail with both an upper keel and a lower fin fold, and a line of small 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 along the middle of its back.
More active at night than during the day when it is usually buried in sediment, the bluntnose stingray is a predator of small 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. This species is aplacental viviparous, in which the unborn young are nourished initially by yolk, and later histotroph ("uterine milk") produced by their mother. Females give birth to 1–6 pups every May 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 11–12 months, most of which consists of a period of arrested embryonic development
Embryonic diapause
Delayed Implantation or Embryonic Diapause is a reproductive strategy used by approximately 100 different mammals in seven or eight different orders. In embryonic diapause, the embryo does not immediately implant in the uterus, but is maintained in a state of dormancy. Little to no development...
. 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 bluntnose stingray is potentially dangerous to unwary beachgoers. 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...
, as it is widely distributed, common, and minimally threatened by commercial fisheries
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
.
Taxonomy and phylogeny
French naturalistNaturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Charles Alexandre Lesueur
Charles Alexandre Lesueur
Charles Alexandre Lesueur was a French naturalist, artist and explorer.Pictured here is the oil portrait by Charles Willson Peale of Charles-Alexandre Lesueur...
originally described the bluntnose stingray from specimens collected in Little Egg Harbor
Little Egg Harbor
Little Egg Harbor is a brackish bay along the coast of southeast New Jersey. It was originally called Egg Harbor by the Dutch sailors because of the eggs found in nearby gull nests.The bay is part of the Intracoastal Waterway.-External links:...
off the U.S. State
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...
of New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
. He published his account in an 1817 volume of the Journal of the Academy of Natural Sciences of Philadelphia, and named the new species Raja say in honor of Thomas Say
Thomas Say
Thomas Say was an American naturalist, entomologist, malacologist, herpetologist and carcinologist. A taxonomist, he is often considered to be the father of descriptive entomology in the United States. He described more than 1,000 new species of beetles and over 400 species of insects of other...
, one of the founding members of the Academy
United States National Academy of Sciences
The National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine." As a national academy, new members of the organization are elected annually by current members, based on their distinguished and...
. The species was moved to the genus Dasyatis by subsequent authors. In 1841, German biologists Johannes Peter Müller
Johannes Peter Müller
Johannes Peter Müller , was a German physiologist, comparative anatomist, and ichthyologist not only known for his discoveries but also for his ability to synthesize knowledge.-Early years and education:...
and Friedrich Gustav Jakob Henle
Friedrich Gustav Jakob Henle
Friedrich Gustav Jakob Henle was a German physician, pathologist and anatomist. He is credited with the discovery of the loop of Henle in the kidney. His essay "On Miasma and Contagia" was an early argument for the germ theory of disease...
erroneously gave the specific epithet as sayi in their Systematische Beschreibung der Plagiostomen, which thereafter became the typical spelling used in literature. Recently, there has been a push to use the correct original spelling again, though it has also been proposed that the International Commission on Zoological Nomenclature
International Commission on Zoological Nomenclature
The International Commission on Zoological Nomenclature is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 28 members from 20 countries, mainly practicing zoological taxonomists...
(ICZN) officially emend the spelling to sayi, for consistency with previous usage.
Lisa Rosenberger's 2001 phylogenetic analysis, based on morphological
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....
characters, found that the bluntnose stingray is one of the more basal members of its genus, and that it is a sister species to the diamond stingray
Diamond stingray
The diamond stingray is a species of stingray in the family Dasyatidae. It is found in the coastal waters of the eastern Pacific Ocean from southern California to northern Chile, and around the Galápagos and Hawaiian Islands...
(D. dipterura) of the western Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. The two species 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...
, some three million years ago.
Distribution and habitat
The bluntnose stingray is found in the western Atlantic OceanAtlantic 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...
, from Chesapeake Bay
Chesapeake Bay
The Chesapeake Bay is the largest estuary in the United States. It lies off the Atlantic Ocean, surrounded by Maryland and Virginia. The Chesapeake Bay's drainage basin covers in the District of Columbia and parts of six states: New York, Pennsylvania, Delaware, Maryland, Virginia, and West...
southward through the Florida Keys
Florida Keys
The Florida Keys are a coral archipelago in southeast United States. They begin at the southeastern tip of the Florida peninsula, about south of Miami, and extend in a gentle arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry...
, the northern 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...
, and the Greater
Greater Antilles
The Greater Antilles are one of three island groups in the Caribbean. Comprising Cuba, Jamaica, Hispaniola , and Puerto Rico, the Greater Antilles constitute almost 90% of the land mass of the entire West Indies.-Greater Antilles in context :The islands of the Caribbean Sea, collectively known as...
and Lesser Antilles
Lesser Antilles
The Lesser Antilles are a long, partly volcanic island arc in the Western Hemisphere. Most of its islands form the eastern boundary of the Caribbean Sea with the Atlantic Ocean, with the remainder located in the southern Caribbean just north of South America...
; on rare occasions it is found as far north as New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
and 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...
, as far south as 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...
, and as far west as Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. It is absent from the southern Gulf of Mexico and the Caribbean
Caribbean Sea
The Caribbean Sea is a sea of the Atlantic Ocean located in the tropics of the Western hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles, and to the east by the Lesser Antilles....
coast of Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
. Reports of this species from off Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
and 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...
likely represent misidentifications of the groovebelly stingray
Groovebelly stingray
The groovebelly stingray, Dasyatis hypostigma, called the butter stingray by fishery workers, is a species of stingray in the family Dasyatidae. It is found over sandy or muddy bottoms in shallow coastal waters off southern Brazil, and probably Uruguay and Argentina...
(D. hypostigma).
Common in 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 such as 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, lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...
s, and estuaries, the bluntnose stingray is a bottom-dwelling species usually found at a depth of 1–10 m (3.3–32.8 ft), though it has been recorded from as deep as 20 m (65.6 ft). It frequents sandy or muddy flats, preferring water with a salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
of 25–43 ppt
Parts-per notation
In science and engineering, the parts-per notation is a set of pseudo units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement...
and a temperature of 12–33 °C (53.6–91.4 F). Adult bluntnose stingrays are seldom found in seagrass
Seagrass
Seagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully saline environments.-Ecology:...
meadows or shoals, though the latter serves as a habitat for young rays. Along the U.S. East Coast, schools of bluntnose stingrays migrate
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...
long distances northward into bays and estuaries to spend the summer, and move back to southern offshore waters for winter.
Description
The bluntnose stingray has a diamond-shaped pectoral fin disc about a sixth wider than long, with broadly rounded outer corners. The leading margins of the disc are nearly straight and converge at the tip of the snout at up to a 130° angle; the anterior disc shape distinguishes this species from the similar Atlantic stingrayAtlantic stingray
The Atlantic stingray is a species of stingray in the family Dasyatidae, common along the Atlantic coast of North America from Chesapeake Bay to Mexico, including brackish and freshwater habitats. It may be distinguished from other stingrays in the area by its relatively elongated snout...
(D. sabina), which has a longer, more acute snout. The mouth is curved, with a central projection on the upper jaw that fits into an indentation on the lower jaw. There is a row of five papilla
Papilla (fish mouth structure)
The papilla, in certain kinds of fish, particularly rays, sharks, and catfish, are small lumps of dermal tissue found in the mouth, where they are "distributed uniformly on the tongue, palate, and pharynx"...
e across the floor of the mouth, with the outermost pair smaller and set apart from the others. There are 36–50 upper tooth rows; the teeth have quadrangular bases and 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. The tooth crowns are rounded in females and juveniles, while those of males in breeding condition are triangular and pointed. The pelvic fins are triangular with rounded tips.
The whip-like tail measures over one and a half times as long as the disc and bears one or two long, serrated stinging spines on top, about a quarter of the tail length back from the base. The second spine, if present, is a replacement that periodically grows in front of the existing spine. Behind the spine, there are well-developed upper and lower fin folds, with the lower fold longer and wider than the upper. Small thorns or tubercles are found in a midline row from behind the eyes to the base of the tail spine, increasing in number with age. Adults also have prickles before and behind the eyes and on the outer parts of the disc. The dorsal coloration is grayish, reddish, or greenish brown; some individuals also possess bluish spots, are darker towards the sides and rear, or have a thin white disc margin. The ventral surface is whitish, sometimes with a dark disc margin or dark blotches. A record off French Guyana gives the maximum disc width of this species as 1 m (3.3 ft), but that specimen may have been misidentified and other sources give a maximum disc width of no more than 0.78 m (2.6 ft). Females grow larger than males.
Biology and ecology
The bluntnose stingray has generally nocturnal habits and spends much of the day buried in the substrateSubstrate (marine biology)
Stream substrate is the material that rests at the bottom of a stream. There are several classification guides. One is:*Mud – silt and clay.*Sand – Particles between 0.06 and 2 mm in diameter.*Granule – Between 2 and 4 mm in diameter....
. It has been known to follow the rising tide
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
to forage in water barely deep enough to cover its body. This species preys upon small 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, including 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, annelid worms, and bivalve and gastropod molluscs, and bony fishes. It mainly targets benthic and burrowing organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
s, but also opportunistically takes free-swimming prey. 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...
, this species feeds predominantly on 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, and its overall dietary composition is virtually identical to that of the roughtail stingray
Roughtail stingray
The roughtail stingray 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...
(D. centroura), with which it shares the bay. The bluntnose stingray is preyed upon by larger fishes such as the bull shark
Bull shark
The bull shark, Carcharhinus leucas, also known as Zambezi shark or unofficially known as Zambi in Africa and Nicaragua shark in Nicaragua, is a shark common worldwide in warm, shallow waters along coasts and in rivers...
(Carcharhinus leucas). Known parasites of this species include the tapeworms Acanthobothrium brevissime and Kotorella pronosoma, 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 Listrocephalos corona, and the trematodes Monocotyle pricei and Multicalyx cristata.
Like other stingrays, the bluntnose stingray 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 initially sustained by yolk. Later in development, finger-like extensions of the uterine 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" surround the embryo and deliver 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...
and 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...
-rich histotroph ("uterine milk") produced by the mother. 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...
in adult females are functional. Mating occurs during a well-defined period from April to June, peaking in May, with the males presumably using their pointed teeth to grasp the females for copulation. However, embryonic development halts at the blastoderm
Blastoderm
-In amniotes:A blastoderm is the layer of cells formed at one pole of macrolecithal eggs such as the yolky egg of birds. The yolk prevents the division from taking place through the egg, resulting in meroblastic cleavage during the many cleavage divisions...
stage, shortly after the formation of the zygote
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...
, and does not resume for approximately ten months. In the spring of the following year, the embryos rapidly mature over a period of 10–12 weeks. This period of embryonic diapause
Embryonic diapause
Delayed Implantation or Embryonic Diapause is a reproductive strategy used by approximately 100 different mammals in seven or eight different orders. In embryonic diapause, the embryo does not immediately implant in the uterus, but is maintained in a state of dormancy. Little to no development...
may reflect the greater availability of food in the spring.
Including the extended period of diapause, the 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:...
lasts around 11–12 months, with 1–6 young being born in mid to late May. In 1941, in a shallow channel between Chincoteague Island and Cape Charles
Cape Charles
Cape Charles may refer to:*Cape Charles, Virginia, a town in Northampton County, Virginia*Cape Charles , headland or cape in Northampton County, Virginia...
, 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...
, several large bluntnose stingrays were observed repeatedly breaking the surface and swimming rapidly in straight lines, some with their tails thrashing in the air; others were seen rising slowly to the surface and "hanging" for several minutes. One of the rays was hooked and the shock of capture caused it to release five near-term fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
es, suggesting that this activity may have been related to parturition. The aborted young were pale with small yolk sac
Yolk sac
The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...
s, and a swelling in the place of their tail spines. Females begin ovulating
Ovulation
Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...
a new batch of eggs immediately after giving birth, indicating that they have an annual reproductive cycle. Newborn rays measure 15–17 cm (5.9–6.7 in) across and weigh 170–250 g (6–8.8 oz). Males mature sexually
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...
at disc width of 30–36 cm (11.8–14.2 in) and a weight of 3–6 kg (6.6–13.2 lb), while females mature at a disc width of 50–54 cm (19.7–21.3 in) and a weight of 7–15 kg (15.4–33.1 lb).
Human interactions
The bluntnose stingray is not aggressive, though it will defend itself if stepped on or otherwise incited. Its tail spine can inflict an excruciating injury, and can easily pierce leatherLeather
Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide. It can be produced through different manufacturing processes, ranging from cottage industry to heavy industry.-Forms:...
or rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
footwear. The paralytic
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
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...
delivered may have potentially life-threatening effects on those with heart or respiratory problems, and is the subject of biomedical and neurobiological research. This species is popular with ecotourist
Ecotourism
Ecotourism is a form of tourism visiting fragile, pristine, and usually protected areas, intended as a low impact and often small scale alternative to standard commercial tourism...
divers. Abundant and widespread, the bluntnose stingray is caught 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...
by commercial
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
trawl and 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...
fisheries operating in nearshore U.S. waters; these activities are not a threat to its population, as most captured rays are released alive. The impact of fishing in the southern parts of its range is uncertain, but is unlikely to significantly affect the species as a whole as these activities occur outside its centers of distribution. As a result, the International Union for Conservation of Nature has listed the bluntnose 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...
.