Dasyatis acutirostra
Encyclopedia
The sharpnose stingray (Dasyatis acutirostra) is a little-known species
of stingray
in the family
Dasyatidae, found off southern Japan
and in the East China Sea
. With a rounded pectoral fin disc and a long, projecting snout, D. acutirostra resembles (and was historically confused with) the smaller pale-edged stingray
(D. zugei). A number of characteristics differentiate this species from D. zugei, including larger eyes and the absence of a dorsal fin fold on the tail. The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened
, as its restricted distribution renders it vulnerable to increases in fishing pressure.
with a description of D. acutirostra, in the Japanese Journal of Ichthyology. The specific epithet comes from the Latin
acuti ("sharp") and rostra ("snout"). The type specimen is an adult male 72.5 cm (28.5 in) across, trawled from the East China Sea
.
off Ecuador
. Like most other stingrays this species is benthic in nature.
s. There is a curtain of skin between the nares, with a fringed, straight posterior margin. The mouth is slightly curved and lacks papilla
e on the floor. There are 40–51 upper tooth rows and 39–49 lower tooth rows, arranged with a quincunx
pattern into pavement-like surfaces. The teeth of adult males have pointed cusps unlike in juveniles and females. The pelvic fins are wide and triangular. The tail is whip-like and longer than the disc, and bears 1-2 stinging spines on the upper surface. A subtle dorsal keel and low ventral fin fold are present behind the spine.
There is a row of 30 tubercles along the midline of the back, and another row of 16 tubercles in front of the spine. The tail behind the spine is covered by small denticles. The coloration is light brown above and white below. The largest known specimen has a disc width of 72.5 cm (28.5 in). This species can be distinguished from the similar D. zugei by a larger eyeball size, the absence of a dorsal fin fold on the tail, a larger maturation size, and various meristic characters.
fishery
catches operating off Japan and elsewhere, though specific utilization data is required. The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened
, as it would be highly susceptible to increasing fishing pressure given its possibly limited geographic distribution.
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, found off southern Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and in the East China Sea
East China Sea
The East China Sea is a marginal sea east of China. It is a part of the Pacific Ocean and covers an area of 1,249,000 km² or 750,000 square miles.-Geography:...
. With a rounded pectoral fin disc and a long, projecting snout, D. acutirostra resembles (and was historically confused with) the smaller 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). A number of characteristics differentiate this species from D. zugei, including larger eyes and the absence of a dorsal fin fold on the tail. The International Union for Conservation of Nature (IUCN) has assessed this species 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...
, as its restricted distribution renders it vulnerable to increases in fishing pressure.
Taxonomy
Prior to being scientifically described, D. acutirostra has been confused for D. zugei; the two species have been confounded by various authors since at least Jordan and Fowler's 1903 review of Japanese elasmobranchs. In 1988, Kiyonori Nishida and Kazuhiro Nakaya published a study of the D. zugei species complexSpecies 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...
with a description of D. acutirostra, in the Japanese Journal of Ichthyology. The specific epithet comes from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
acuti ("sharp") and rostra ("snout"). The type specimen is an adult male 72.5 cm (28.5 in) across, trawled from the East China Sea
East China Sea
The East China Sea is a marginal sea east of China. It is a part of the Pacific Ocean and covers an area of 1,249,000 km² or 750,000 square miles.-Geography:...
.
Distribution and habitat
Dasyatis acutirostra is known from off southern Japan and in the East China Sea at a depth of 53–142 m (173.9–465.9 ft), though there is also a possible record of this species from the Gulf of GuayaquilGulf of Guayaquil
The Gulf of Guayaquil is a large body of water of the Pacific Ocean in western South America. Its northern limit is the city of Salinas, in Ecuador, and its southern limit is Punta Pariñas, in Peru.The gulf takes its name from the city of Guayaquil...
off Ecuador
Ecuador
Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...
. Like most other stingrays this species is benthic in nature.
Description
The pectoral fin disc of D. acutirostra is about as wide as it is long, with rounded outer margins and concave leading margins merging with a long, triangular snout. The eyes are small and followed by 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 curtain of skin between the nares, with a fringed, straight posterior margin. The mouth is slightly curved and lacks 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 on the floor. There are 40–51 upper tooth rows and 39–49 lower tooth rows, 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 pavement-like surfaces. The teeth of adult males have pointed cusps unlike in juveniles and females. The pelvic fins are wide and triangular. The tail is whip-like and longer than the disc, and bears 1-2 stinging spines on the upper surface. A subtle dorsal keel and low ventral fin fold are present behind the spine.
There is a row of 30 tubercles along the midline of the back, and another row of 16 tubercles in front of the spine. The tail behind the spine is covered by small denticles. The coloration is light brown above and white below. The largest known specimen has a disc width of 72.5 cm (28.5 in). This species can be distinguished from the similar D. zugei by a larger eyeball size, the absence of a dorsal fin fold on the tail, a larger maturation size, and various meristic characters.
Biology and ecology
Virtually nothing is known of the natural history of D. acutirostra. One male specimen 35.4 cm (13.9 in) was immature, while another 72.5 cm (28.5 in) across was mature. It is presumably aplacental viviparous like other stingrays.Human interactions
Dasyatis acutirostra likely forms part of coastal bottom trawl and set netFishing 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...
fishery
Fishery
Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...
catches operating off Japan and elsewhere, though specific utilization data is required. The International Union for Conservation of Nature (IUCN) has assessed this species 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...
, as it would be highly susceptible to increasing fishing pressure given its possibly limited geographic distribution.