Sharpsnout stingray
Encyclopedia
The sharpsnout stingray or wingfin stingray, Dasyatis geijskesi, is a species
of stingray
in the family
Dasyatidae, found from off Venezuela
to northern Brazil
. It inhabits shallow, brackish water
, shifting towards the coast in the dry season
and away from it in the rainy season. Typically measuring 70 cm (27.6 in) across, this dark brown ray is easily identifiable by its long, projecting snout and elongated, acutely pointed pelvic fins. Its diet consists of bottom-dwelling invertebrate
s. Reproduction is aplacental viviparous, with females bearing 1–3 pups annually. Naturally uncommon and slow-reproducing, the sharpnose stingray is under pressure by both artisanal
and commercial fisheries
, leading the International Union for Conservation of Nature (IUCN) to assess it as Near Threatened
.
Zoologische Mededelingen, based on a juvenile male caught off Suriname
with a disc length of 36 cm (14.2 in). The whereabouts of this type specimen is presently unknown. In a 2001 phylogenetic analysis based on morphological characters
, Lisa Rosenberger found that the longnose stingray
(D. guttata) is the sister species of the sharpsnout stingray, and that the two form a clade
with the pale-edged stingray
(D. zugei), the pearl stingray
(D. margaritella), the sharpnose stingray
(Himantura gerrardi), and the smooth butterfly ray
(Gymnura micrura, included in the study as an outgroup
). These results support the growing consensus that neither Dasyatis
nor Himantura
are monophyletic.
, the sharpsnout stingray is found in nearshore, brackish water
s along the northeastern coast of South America
, from Venezuela
and Trinidad and Tobago
to northern Brazil
; many occur in the estuarine
area affected by the freshwater
discharge of the Amazon River
. It favors muddy habitats 5–25 m (16.4–82 ft) deep, with low visibility. However, Uyeno et al (1983) gave a depth of 810 m (2,657.5 ft) for this species. The sharpsnout stingray conducts annual movements that are affected by salinity
, entering coastal bays such as Marajó Bay during the rainy season and shifting to offshore waters during the rainy season.
s. There is a flap of skin between the nares, with a finely fringed posterior margin. The line of the mouth is slightly indented at the center. The upper and lower jaws both contain 56–68 tooth rows; the teeth are blunt and arranged with a quincunx
pattern. A transverse row of 5 papilla
e are present on the floor of the mouth.
The pelvic fins are distinctive, being over twice as long as wide with a gently sinuous trailing margin, and tapering to an acute tip that sometimes extends past the disc. The whip-like tail measures over twice the length of the disc and bears 1–2 serrated spines on top. Posterior to the spines are a subtle dorsal keel and a ventral fin fold about half as long as the disc. A band of small tubercles runs along the dorsal midline from behind the eyes to the base of the tail (excluding a posterior portion of the disc), with larger tubercles in a central row and on each "shoulder". More conical tubercles are scattered over the upper surface of the tail past the spines. The coloration is a uniform brown above, and white below darkening towards the disc margin. This species typically attains a disc width of 70 cm (27.6 in), but individuals up to 1.5 m (4.9 ft) across have been recorded.
s such as worm
s, crustacean
s, and molluscs, excavating them from the substrate and grinding them apart with its pavement-like teeth. Like other stingrays, this species is aplacental viviparous, with females giving birth to 1–3 young every year. Similarly to the Colares stingray
(D. colarensis), the annual movements of this ray may relate to reproduction as most females found near the coast are newly impregnated. Younger individuals have proportionately longer tails (measuring up to three times the disc width) than adults.
ous tail spines of the sharpsnout stingray are potentially hazardous to humans. This species is caught by hook-and-line or in nets
; it is used for food by subsistence fishers
, but is not favored because its flesh is a dark reddish color. Sharpsnout stingrays also form part of the bycatch
of artisanal and commercial fisheries
targeting large catfish
in the Amazon estuary, while increasing interest in using stingrays for minced fish products may intensify fishing pressure on this species in the future. Because of these threats and the slow reproductive rate of this ray, the International Union for Conservation of Nature (IUCN) has assessed it as 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
Stingray
The stingrays are a group of rays, which are cartilaginous fishes related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes, and consist of eight families: Hexatrygonidae , Plesiobatidae , Urolophidae , Urotrygonidae , Dasyatidae , Potamotrygonidae The...
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, found from off 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 northern 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...
. It inhabits shallow, 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"...
, shifting towards the coast in the dry season
Dry season
The dry season is a term commonly used when describing the weather in the tropics. The weather in the tropics is dominated by the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year...
and away from it in the rainy season. Typically measuring 70 cm (27.6 in) across, this dark brown ray is easily identifiable by its long, projecting snout and elongated, acutely pointed pelvic fins. Its diet consists of bottom-dwelling 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. Reproduction is aplacental viviparous, with females bearing 1–3 pups annually. Naturally uncommon and slow-reproducing, the sharpnose stingray is under pressure by both 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 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...
, leading the International Union for Conservation of Nature (IUCN) to assess it 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
Dutch ichthyologist Marinus Boeseman described the sharpsnout stingray in a 1948 issue of the scientific journalScientific journal
In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past...
Zoologische Mededelingen, based on a juvenile male caught off Suriname
Suriname
Suriname , officially the Republic of Suriname , is a country in northern South America. It borders French Guiana to the east, Guyana to the west, Brazil to the south, and on the north by the Atlantic Ocean. Suriname was a former colony of the British and of the Dutch, and was previously known as...
with a disc length of 36 cm (14.2 in). The whereabouts of this type specimen is presently unknown. In a 2001 phylogenetic analysis based on morphological characters
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....
, Lisa Rosenberger found that the longnose stingray
Longnose stingray
The longnose stingray, Dasyatis guttata, is a species of stingray in the family Dasyatidae, native to the western Atlantic Ocean from the southern Gulf of Mexico to Brazil. Found in coastal waters no deeper than , this demersal species favors muddy or sandy habitats...
(D. guttata) is the sister species of the sharpsnout stingray, and that the two 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 pale-edged stingray
Pale-edged stingray
The pale-edged stingray or sharpnose stingray is a species of stingray in the family Dasyatidae, found in the Indian and Pacific Oceans from India to the western Malay Archipelago and southern Japan. This bottom-dwelling ray is most commonly found over sandy areas shallower than , as well as in...
(D. zugei), the pearl stingray
Pearl stingray
The pearl stingray is a little-known species of stingray in the family Dasyatidae, found in shallow coastal waters from Mauritania to Angola. Growing to across, this species has a rounded pectoral fin disc with a pointed snout, and a wide band of dermal denticles over the back in adults...
(D. margaritella), the sharpnose stingray
Sharpnose stingray
The whitespotted whipray or sharpnose stingray is a species of stingray in the family Dasyatidae. It is found in coastal regions including estuaries, in the Indo-Pacific, and has also been recorded in the Ganges River. It reaches a maximum length of 2 metres . As presently defined, it is probably...
(Himantura gerrardi), and the smooth butterfly ray
Smooth butterfly ray
The smooth butterfly ray is a species of fish in the Gymnuridae family. It is found in Belize, Brazil, Cameroon, Colombia, the Democratic Republic of the Congo, Costa Rica, French Guiana, Gambia, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama, Senegal, Sierra Leone, Suriname, Trinidad and...
(Gymnura micrura, included in the study as an outgroup
Outgroup
In cladistics or phylogenetics, an outgroup is a group of organisms that serves as a reference group for determination of the evolutionary relationship among three or more monophyletic groups of organisms....
). These results support the growing consensus that neither Dasyatis
Dasyatis
Dasyatis is a genus of stingray. The members of the genus Neotrygon were formerly included in Dasyatis.-Species:...
nor Himantura
Himantura
Himantura is a genus of stingray in the family Dasyatidae, commonly known as the whiprays. They are distinguished from other stingrays by a long, slender tail without tail folds. Himantura species are very morphologically diverse and the genus may be polyphyletic...
are monophyletic.
Distribution and habitat
One of the less common stingrays within its rangeRange (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:...
, the sharpsnout stingray is found in nearshore, 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"...
s along the northeastern coast of South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, 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...
and Trinidad and Tobago
Trinidad and Tobago
Trinidad and Tobago officially the Republic of Trinidad and Tobago is an archipelagic state in the southern Caribbean, lying just off the coast of northeastern Venezuela and south of Grenada in the Lesser Antilles...
to northern 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...
; many occur in the estuarine
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
area affected by the freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
discharge of the Amazon River
Amazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...
. It favors muddy habitats 5–25 m (16.4–82 ft) deep, with low visibility. However, Uyeno et al (1983) gave a depth of 810 m (2,657.5 ft) for this species. The sharpsnout stingray conducts annual movements that are affected by 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...
, entering coastal bays such as Marajó Bay during the rainy season and shifting to offshore waters during the rainy season.
Description
The pectoral fin disc of the sharpsnout stingray is about as wide as long, with strongly concave leading margins and rounded corners. The snout is long and projecting, measuring 39–54% as long as the disc is wide. The eyes are minute and followed by much larger spiracleSpiracle
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 flap of skin between the nares, with a finely fringed posterior margin. The line of the mouth is slightly indented at the center. The upper and lower jaws both contain 56–68 tooth rows; the teeth are blunt and 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. A transverse row of 5 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 are present on the floor of the mouth.
The pelvic fins are distinctive, being over twice as long as wide with a gently sinuous trailing margin, and tapering to an acute tip that sometimes extends past the disc. The whip-like tail measures over twice the length of the disc and bears 1–2 serrated spines on top. Posterior to the spines are a subtle dorsal keel and a ventral fin fold about half as long as the disc. A band of small tubercles runs along the dorsal midline from behind the eyes to the base of the tail (excluding a posterior portion of the disc), with larger tubercles in a central row and on each "shoulder". More conical tubercles are scattered over the upper surface of the tail past the spines. The coloration is a uniform brown above, and white below darkening towards the disc margin. This species typically attains a disc width of 70 cm (27.6 in), but individuals up to 1.5 m (4.9 ft) across have been recorded.
Biology and ecology
The sharpsnout stingray feeds on small burrowing invertebrateInvertebrate
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 such as worm
Worm
The term worm refers to an obsolete taxon used by Carolus Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate animals, and stems from the Old English word wyrm. Currently it is used to describe many different distantly-related animals that typically have a long cylindrical...
s, 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, and molluscs, excavating them from the substrate and grinding them apart with its pavement-like teeth. Like other stingrays, this species is aplacental viviparous, with females giving birth to 1–3 young every year. Similarly to the Colares stingray
Colares stingray
The Colares stingray, Dasyatis colarensis, is a species of stingray in the family Dasyatidae, native to the shallow brackish waters of the Amazon River estuary in northern Brazil. This species inhabits inshore bays during the dry season and moves away from the coast in the rainy season...
(D. colarensis), the annual movements of this ray may relate to reproduction as most females found near the coast are newly impregnated. Younger individuals have proportionately longer tails (measuring up to three times the disc width) than adults.
Human interactions
The sharp, 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 tail spines of the sharpsnout stingray are potentially hazardous to humans. This species is caught by hook-and-line or in nets
Fishing net
A fishing net or fishnet is a net that is used for fishing. Fishing nets are meshes usually formed by knotting a relatively thin thread. Modern nets are usually made of artificial polyamides like nylon, although nets of organic polyamides such as wool or silk thread were common until recently and...
; it is used for food by subsistence fishers
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...
, but is not favored because its flesh is a dark reddish color. Sharpsnout stingrays also form part of the bycatch
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...
of artisanal and 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...
targeting large catfish
Catfish
Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...
in the Amazon estuary, while increasing interest in using stingrays for minced fish products may intensify fishing pressure on this species in the future. Because of these threats and the slow reproductive rate of this ray, the International Union for Conservation of Nature (IUCN) has assessed it 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...
.