Yellow stingray
Encyclopedia
The yellow stingray is a species of stingray
in the family
Urotrygonidae
, found in the tropical western Atlantic Ocean
from North Carolina
to Trinidad
. This bottom-dwelling species inhabits sandy, muddy, or seagrass
bottoms in shallow inshore waters, commonly near coral reef
s. Reaching no more than 36 cm (14.2 in) across, the yellow stingray has a round pectoral fin disc and a short tail with a well-developed caudal fin. It has a highly variable but distinctive dorsal color pattern consisting of either light-on-dark or dark-on-light reticulations forming spots and blotches, and can rapidly change the tonality of this coloration to improve its camouflage
.
Relatively sedentary during the day, the yellow stingray feeds on small invertebrate
s and bony fishes. When hunting it may undulate its disc to uncover buried prey, or lift the front of its disc to form a "cave" attractive to shelter-seeking organism
s. This species is aplacental viviparous, meaning that the developing embryo
s are sustained initially by yolk and later by histotroph ("uterine milk"). Females bear two litters of up to seven young per year in seagrass, following a gestation period of 5–6 months. Though innocuous towards humans, the yellow stingray can inflict a painful injury with its venom
ous tail spine. This species is taken as bycatch
by commercial fisheries and collected for the aquarium trade
; it may also be negatively affected by habitat degradation. Nevertheless, it remains common and widespread, which has led the International Union for Conservation of Nature (IUCN) to list it under Least Concern
.
Georges Cuvier
originally described the yellow stingray as Raia jamaicensis in 1816, in Le Règne Animal distribué d'après son organisation pour servir de base à l'histoire naturelle des animaux et d'introduction à l'anatomie comparée. He based his account on specimens obtained from Jamaica
, though no type specimens were designated. Subsequent authors moved this species to the genus Urolophus
, and then to the genus Urobatis (some literature still refers to this species as Urolophus jamaicensis). Other common name
s used for this ray include the yellow-spotted ray, the round ray, and the maid ray.
Nathan Lovejoy's 1996 phylogenetic analysis, based on morphology
, found that the yellow stingray is the most basal member of a clade
that also contains Pacific Urobatis species and the genus Urotrygon of Central
and South America
. This finding would render Urobatis polyphyletic, though further study is warranted to elucidate the relationships between these taxa.
The yellow stingray is found throughout the inshore waters of the Gulf of Mexico
(where it is the only representative of its family) and the Caribbean Sea
, including Florida
, the Bahamas, and the Greater
and Lesser Antilles
to Trinidad
. On rare occasions, it ranges as far north as Cape Lookout
in North Carolina
. It is quite abundant in the Florida Keys
and parts of the Antilles, and rather uncommon elsewhere. Off Mexico
, this species occupies a salinity
range of 26–40 ppt
.
Benthic in nature, the yellow stingray inhabits coastal habitats such as bay
s, lagoon
s, estuaries, and low-energy surf zone
s, and has been reported from the water's edge to a depth of 25 m (82 ft). It particularly favors insular
hard-bottomed habitats with a dense encrustation of sessile
invertebrate
s (termed live-bottom habitats), but can also be found over sand
, mud
or seagrass
(Thalassia
), sometimes in the vicinity of coral reef
s. Off Jamaica, large numbers of yellow stingrays, up to one per square meter, gather beneath the aerial root
s of mangrove
trees used as roosts by cattle egret
s (Bubulcus ibis); it is theorized that the birds' droppings
sustain invertebrates that attract the rays. There is no evidence of seasonal migration
, though during the spring females tend to be found closer to shore than males.
s. There is a narrow curtain of skin between the nostril
s, with a fringed posterior margin. The mouth is nearly straight and contains a transverse row of 3–5 papilla
e on the floor. There are 30–34 tooth rows in the upper jaw and a similar number in the lower jaw, arranged into bands. The teeth are broad-based, with low, blunt crowns in females and juveniles, and tall, pointed cusps in adult males. The teeth of males are more widely spaced than those of females. The pelvic fins have nearly straight leading margins and rounded trailing margins.
The tail is stout and flattened, comprising less than half the total length, and terminates in a small, leaf-shaped caudal fin about a quarter high as long, that is continuous around the last vertebra. A serrated spine is positioned about halfway along the tail. Newborn rays are smooth-skinned; shortly after birth small, blunt tubercle
s appear in the middle of the back, which in larger adults extends to between the eyes, the "shoulders", and the base of the tail. Adults also develop recurved thorns along the upper margin of the caudal fin. The color and pattern of the yellow stingray varies significantly among individuals, though most follow one of two schemes: minute dark green or brown reticulations on a light background, or dense white, yellow, or golden spots on a dark green or brown background. The underside is yellowish, greenish, or brownish white, with small darker spots toward the disc margin and the tail. This species is capable of rapidly changing the tone and contrast of its coloration to better match its environment.
of around 20000 square metre, with individuals covering only a portion of the entire area on any particular day. It favors the boundaries between different terrain, such as sand and reef. Its periscopic
eyes give it a 360° panoramic view of its surroundings; each eye bears an elaborate covering or "operculum" that allows fine control over the amount of light entering the pupil
. Therefore, the resting ray is well-equipped to detect approaching predators, which may potentially include any large carnivorous fish such as the tiger shark
(Galeocerdo cuvier). The yellow stingray is most sensitive to sounds of 300–600 Hertz
, which is fairly typical among sharks and rays that have been investigated thus far. It and other stingrays have a large brain
relative to other rays, comprising around 1–2% of the body weight.
The diet of the yellow stingray is poorly documented but includes shrimp
s, and likely also worm
s, clam
s, and small bony fishes. Typically, the ray will settle over a prey item and trap it against the bottom, whereupon it is manipulated to the mouth with motions of the disc. Like the related round stingray
(U. halleri), this species sometimes uses undulations of its disc margins to excavate pits and reveal buried prey. It has also been observed raising the front of its disc to create a shaded "cave", to attract shelter-seeking organisms. Known parasites of the yellow stingray include the tapeworms Acanthobothrium cartagenensis, Phyllobothrium kingae, Discobothrium caribbensis, Rhinebothrium magniphallum, and R. biorchidum, and the monogenea
n Dendromonocotyle octodiscus.
Like other stingrays, the yellow stingray is aplacental viviparous: at first the embryo
s are sustained by yolk, which is later supplanted by histrotroph ("uterine milk", rich in protein
s and lipid
s), delivered by the mother through numerous finger-like extensions of the uterine
epithelium
called "trophonemata". Mature females have two functional uteruses, with the left used more than the right. Except in a few individuals, only the left ovary
is functional. The reproductive cycle is biannual with a 5–6 month long gestation period
. The first period of ovulation
occurs from January to April, peaking in late February and early March, with birthing from June to September, peaking in late July and early August. The second period of ovulation occurs from August to September, with birthing from November to January. The two cycles overlap as vitellogenesis
(yolk formation) begins while the female is still pregnant.
Courtship and mating in the yellow stingray involves one or more males closely following a female, seeking to bite and grip the rear margin of her disc; the high, pointed teeth of males serve to aid in this endeavor. Once the male successfully holds onto the female, he flips under her so that the two are aligned abdomen-to-abdomen, and inserts a single clasper into her cloaca
. Rival males may attempt to interfere with the mating pair by biting or bumping them. In one observation that took place in water 2.5 m (8.2 ft) deep near Tobacco Caye on the Belize Barrier Reef
, the male pursuit lasted between 30 and 60 seconds and copulation lasted four minutes.
The predominant source of embryonic nutrition is histotroph, which supports a 46-fold weight increase from ovum to near-term fetus
. By the time the embryo is 4.7 cm (1.9 in) across, it has fully resorbed its yolk sac
and external gill
s. The litter size ranges from one to seven. The first litter of the year (spring-summer) is larger than the second (autumn-winter), with the number of offspring increasing with the size of the female; this relationship is not observed for second litter. On the other hand, the newborns of the first litter tend to be slightly smaller than those of the second litter, at an average length of 14.5 cm (5.7 in) versus 15 cm (5.9 in). The second litter's fewer, larger young may reflect the lower temperatures of autumn-winter, which results in slower growth. Seagrass beds serve as important habitat for parturition. The newborns emerge tail-first and are similar in coloration to the adults, though the disc is relatively wider. They also have a small "knob" or "tentacle" that covers most of the spiracle, which is resorbed shortly after birth. Males and females reach sexual maturity
at disc widths of 15–16 cm (5.9–6.3 in) and 20 cm (7.9 in) respectively. The maximum lifespan is 15–25 years.
The International Union for Conservation of Nature (IUCN) has listed the yellow stingray under Least Concern
, citing its wide distribution and high abundance in certain regions. In addition, its small size implies relatively high productivity
, which would make its population more resilient to fishing pressure. This species is not targeted commercially
, but is probably taken incidentally
by inshore fisheries throughout its range. It is also harvested for the home aquarium trade
, being the most frequently available member of its family on the North American market. The extent of this trade has not yet been quantified. Another potential threat is habitat degradation, particularly to seagrass beds. No conservation measures have been enacted for this species.
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...
Urotrygonidae
Urotrygonidae
Urotrygonidae is a family of rays in the order Myliobatiformes, commonly referred to as the American round stingrays or round rays. They are native to the tropical and warm temperate marine waters of the Americas. The two genera in this family were formerly placed within the family Urolophidae,...
, found in the tropical 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 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 Trinidad
Trinidad
Trinidad is the larger and more populous of the two major islands and numerous landforms which make up the island nation of Trinidad and Tobago. It is the southernmost island in the Caribbean and lies just off the northeastern coast of Venezuela. With an area of it is also the fifth largest in...
. This bottom-dwelling species inhabits sandy, muddy, or 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:...
bottoms in shallow inshore waters, commonly near coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
s. Reaching no more than 36 cm (14.2 in) across, the yellow stingray has a round pectoral fin disc and a short tail with a well-developed caudal fin. It has a highly variable but distinctive dorsal color pattern consisting of either light-on-dark or dark-on-light reticulations forming spots and blotches, and can rapidly change the tonality of this coloration to improve its camouflage
Crypsis
In ecology, crypsis is the ability of an organism to avoid observation or detection by other organisms. It may be either a predation strategy or an antipredator adaptation, and methods include camouflage, nocturnality, subterranean lifestyle, transparency, and mimicry...
.
Relatively sedentary during the day, the yellow stingray feeds on 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 and bony fishes. When hunting it may undulate its disc to uncover buried prey, or lift the front of its disc to form a "cave" attractive to shelter-seeking 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. This species is aplacental viviparous, meaning that 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...
s are sustained initially by yolk and later by histotroph ("uterine milk"). Females bear two litters of up to seven young per year in seagrass, following a gestation period of 5–6 months. Though innocuous towards humans, the yellow stingray can inflict a painful injury with its 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. This species is taken as 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...
by commercial fisheries and collected for the aquarium trade
Fishkeeping
Fishkeeping is a popular hobby concerned with keeping fish in a home aquarium or garden pond. There is also a fishkeeping industry, as a branch of agriculture.-Types of fishkeeping systems:...
; it may also be negatively affected by habitat degradation. Nevertheless, it remains common and widespread, which has led the International Union for Conservation of Nature (IUCN) to list it 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...
.
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...
Georges Cuvier
Georges Cuvier
Georges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...
originally described the yellow stingray as Raia jamaicensis in 1816, in Le Règne Animal distribué d'après son organisation pour servir de base à l'histoire naturelle des animaux et d'introduction à l'anatomie comparée. He based his account on specimens obtained from Jamaica
Jamaica
Jamaica is an island nation of the Greater Antilles, in length, up to in width and 10,990 square kilometres in area. It is situated in the Caribbean Sea, about south of Cuba, and west of Hispaniola, the island harbouring the nation-states Haiti and the Dominican Republic...
, though no type specimens were designated. Subsequent authors moved this species to the genus Urolophus
Urolophus
Urolophus is a genus of stingrays in the family Urolophidae.-Species:* New Ireland stingaree, Urolophus armatus Müller & Henle, 1841* Sepia stingray, Urolophus aurantiacus Müller & Henle, 1841...
, and then to the genus Urobatis (some literature still refers to this species as Urolophus jamaicensis). Other common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s used for this ray include the yellow-spotted ray, the round ray, and the maid ray.
Nathan Lovejoy's 1996 phylogenetic analysis, 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 yellow stingray is the most basal member of 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...
that also contains Pacific Urobatis species and the genus Urotrygon of Central
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...
and 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...
. This finding would render Urobatis polyphyletic, though further study is warranted to elucidate the relationships between these taxa.
Distribution and habitat
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...
(where it is the only representative of its family) and the Caribbean Sea
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....
, including 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 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...
to Trinidad
Trinidad
Trinidad is the larger and more populous of the two major islands and numerous landforms which make up the island nation of Trinidad and Tobago. It is the southernmost island in the Caribbean and lies just off the northeastern coast of Venezuela. With an area of it is also the fifth largest in...
. On rare occasions, it ranges as far north as Cape Lookout
Cape Lookout
Cape Lookout can refer to:*Cape Lookout , in the United States*Cape Lookout , in the United States*Cape Lookout...
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...
. It is quite abundant in 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...
and parts of the Antilles, and rather uncommon elsewhere. Off 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...
, this species occupies 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...
range of 26–40 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...
.
Benthic in nature, the yellow stingray inhabits coastal habitats 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, estuaries, and low-energy surf zone
Surf zone
As ocean surface waves come closer to shore they break, forming the foamy, bubbly surface we call surf. The region of breaking waves defines the surf zone. After breaking in the surf zone, the waves continue to move in, and they run up onto the sloping front of the beach, forming an uprush of...
s, and has been reported from the water's edge to a depth of 25 m (82 ft). It particularly favors insular
Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...
hard-bottomed habitats with a dense encrustation of 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 (termed live-bottom habitats), but can also be found over sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
, mud
Mud
Mud is a mixture of water and some combination of soil, silt, and clay. Ancient mud deposits harden over geological time to form sedimentary rock such as shale or mudstone . When geological deposits of mud are formed in estuaries the resultant layers are termed bay muds...
or 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:...
(Thalassia
Thalassia (genus)
Thalassia is a marine seagrass genus comprising 2 species.-Species:T. testudinum Banks ex König is the type specimen. It is native to the Gulf of Mexico and the Caribbean with specimens found as far east as Bermuda. It has a fossil record in the Gulf to the Middle Eocene.T. hemprichii ...
), sometimes in the vicinity of coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
s. Off Jamaica, large numbers of yellow stingrays, up to one per square meter, gather beneath the aerial root
Aerial root
Aerial roots are roots above the ground. They are almost always adventitious. They are found in diverse plant species, including epiphytes such as orchids, tropical coastal swamp trees such as mangroves, the resourceful banyan trees, the warm-temperate rainforest rātā and pōhutukawa Aerial roots...
s of mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
trees used as roosts by cattle egret
Cattle Egret
The Cattle Egret is a cosmopolitan species of heron found in the tropics, subtropics and warm temperate zones. It is the only member of the monotypic genus Bubulcus, although some authorities regard its two subspecies as full species, the Western Cattle Egret and the Eastern Cattle Egret...
s (Bubulcus ibis); it is theorized that the birds' droppings
Guano
Guano is the excrement of seabirds, cave dwelling bats, and seals. Guano manure is an effective fertilizer due to its high levels of phosphorus and nitrogen and also its lack of odor. It was an important source of nitrates for gunpowder...
sustain invertebrates that attract the rays. There is no evidence of seasonal migration
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...
, though during the spring females tend to be found closer to shore than males.
Description
The yellow stingray is small, growing no more than 36 cm (14.2 in) across and 70 cm (27.6 in) long. It has a nearly circular pectoral fin disc slightly longer than wide, with a short, obtuse snout. The eyes are immediately followed by the 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 narrow 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 fringed posterior margin. The mouth is nearly straight and contains a transverse row of 3–5 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 on the floor. There are 30–34 tooth rows in the upper jaw and a similar number in the lower jaw, arranged into bands. The teeth are broad-based, with low, blunt crowns in females and juveniles, and tall, pointed cusps in adult males. The teeth of males are more widely spaced than those of females. The pelvic fins have nearly straight leading margins and rounded trailing margins.
The tail is stout and flattened, comprising less than half the total length, and terminates in a small, leaf-shaped caudal fin about a quarter high as long, that is continuous around the last vertebra. A serrated spine is positioned about halfway along the tail. Newborn rays are smooth-skinned; shortly after birth small, blunt 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 appear in the middle of the back, which in larger adults extends to between the eyes, the "shoulders", and the base of the tail. Adults also develop recurved thorns along the upper margin of the caudal fin. The color and pattern of the yellow stingray varies significantly among individuals, though most follow one of two schemes: minute dark green or brown reticulations on a light background, or dense white, yellow, or golden spots on a dark green or brown background. The underside is yellowish, greenish, or brownish white, with small darker spots toward the disc margin and the tail. This species is capable of rapidly changing the tone and contrast of its coloration to better match its environment.
Biology and ecology
During the day, the yellow stingray is fairly inactive and spends much time buried under a thin layer of sediment or lying motionless in vegetation. Tracking studies have shown that it generally remains within a small home rangeHome range
Home range is the area where an animal lives and travels in. It is closely related to, but not identical with, the concept of "territory".The concept that can be traced back to a publication in 1943 by W. H. Burt, who constructed maps delineating the spatial extent or outside boundary of an...
of around 20000 square metre, with individuals covering only a portion of the entire area on any particular day. It favors the boundaries between different terrain, such as sand and reef. Its periscopic
Periscope
A periscope is an instrument for observation from a concealed position. In its simplest form it consists of a tube with mirrors at each end set parallel to each other at a 45-degree angle....
eyes give it a 360° panoramic view of its surroundings; each eye bears an elaborate covering or "operculum" that allows fine control over the amount of light entering the pupil
Pupil
The pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. It appears black because most of the light entering the pupil is absorbed by the tissues inside the eye. In humans the pupil is round, but other species, such as some cats, have slit pupils. In...
. Therefore, the resting ray is well-equipped to detect approaching predators, which may potentially include any large carnivorous fish such as the tiger shark
Tiger shark
The tiger sharks, Galeocerdo cuvier, is a species of requiem shark and the only member of the genus Galeocerdo. Commonly known as sea tigers, tiger sharks are relatively large macropredators, capable of attaining a length of over . It is found in many tropical and temperate waters, and is...
(Galeocerdo cuvier). The yellow stingray is most sensitive to sounds of 300–600 Hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
, which is fairly typical among sharks and rays that have been investigated thus far. It and other stingrays have a large brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
relative to other rays, comprising around 1–2% of the body weight.
The diet of the yellow stingray is poorly documented but includes 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...
s, and likely also 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, clam
Clam
The word "clam" can be applied to freshwater mussels, and other freshwater bivalves, as well as marine bivalves.In the United States, "clam" can be used in several different ways: one, as a general term covering all bivalve molluscs...
s, and small bony fishes. Typically, the ray will settle over a prey item and trap it against the bottom, whereupon it is manipulated to the mouth with motions of the disc. Like the related round stingray
Round stingray
The round stingray or Haller's round ray, Urobatis halleri, is a species of round ray, family Urolophidae, found in the coastal waters of the eastern Pacific Ocean. It is a small, common ray that feeds mostly on benthic invertebrates. On the beaches of southern California, it is responsible for...
(U. halleri), this species sometimes uses undulations of its disc margins to excavate pits and reveal buried prey. It has also been observed raising the front of its disc to create a shaded "cave", to attract shelter-seeking organisms. Known parasites of the yellow stingray include the tapeworms Acanthobothrium cartagenensis, Phyllobothrium kingae, Discobothrium caribbensis, Rhinebothrium magniphallum, and R. biorchidum, and 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 octodiscus.
Life history
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 are sustained by yolk, which is later supplanted by histrotroph ("uterine milk", rich in 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 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...
s), delivered by the mother through numerous finger-like extensions 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". Mature females have two functional uteruses, with the left used more than the right. Except in a few individuals, 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...
is functional. The reproductive cycle is biannual with a 5–6 month long 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:...
. The first period of ovulation
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...
occurs from January to April, peaking in late February and early March, with birthing from June to September, peaking in late July and early August. The second period of ovulation occurs from August to September, with birthing from November to January. The two cycles overlap as vitellogenesis
Vitellogenesis
Vitellogenesis is the process of yolk formation via nutrients being deposited in the oocyte, or female germ cell involved in reproduction. It starts when the fat body stimulates the release of juvenile hormones and produces vitellogenin protein. It occurs in all animal groups lower than the mammals...
(yolk formation) begins while the female is still pregnant.
Courtship and mating in the yellow stingray involves one or more males closely following a female, seeking to bite and grip the rear margin of her disc; the high, pointed teeth of males serve to aid in this endeavor. Once the male successfully holds onto the female, he flips under her so that the two are aligned abdomen-to-abdomen, and inserts a single clasper into her cloaca
Cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...
. Rival males may attempt to interfere with the mating pair by biting or bumping them. In one observation that took place in water 2.5 m (8.2 ft) deep near Tobacco Caye on the Belize Barrier Reef
Belize Barrier Reef
The Belize Barrier Reef is a series of coral reefs straddling the coast of Belize, roughly offshore in the north and in the south within the country limits...
, the male pursuit lasted between 30 and 60 seconds and copulation lasted four minutes.
The predominant source of embryonic nutrition is histotroph, which supports a 46-fold weight increase from ovum to 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...
. By the time the embryo is 4.7 cm (1.9 in) across, it has fully resorbed its 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...
and external gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s. The litter size ranges from one to seven. The first litter of the year (spring-summer) is larger than the second (autumn-winter), with the number of offspring increasing with the size of the female; this relationship is not observed for second litter. On the other hand, the newborns of the first litter tend to be slightly smaller than those of the second litter, at an average length of 14.5 cm (5.7 in) versus 15 cm (5.9 in). The second litter's fewer, larger young may reflect the lower temperatures of autumn-winter, which results in slower growth. Seagrass beds serve as important habitat for parturition. The newborns emerge tail-first and are similar in coloration to the adults, though the disc is relatively wider. They also have a small "knob" or "tentacle" that covers most of the spiracle, which is resorbed shortly after birth. Males and females reach 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...
at disc widths of 15–16 cm (5.9–6.3 in) and 20 cm (7.9 in) respectively. The maximum lifespan is 15–25 years.
Human interactions
Generally, yellow stingrays pay little heed to divers and can be approached closely. If stepped on or otherwise provoked, however, this ray will defend itself with its tail spine, coated in potent venom. The resulting wound is extremely painful, but seldom life-threatening. Small and docile, the yellow stingray adapts readily to captivity and has reproduced in the aquarium; it requires a large amount of space (at least 180 gal or 684 L) and a fine, deep substrate with minimal ornamentation.The International Union for Conservation of Nature (IUCN) has listed the yellow stingray 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...
, citing its wide distribution and high abundance in certain regions. In addition, its small size implies relatively high productivity
Productivity (ecology)
In ecology, productivity or production refers to the rate of generation of biomass in an ecosystem. It is usually expressed in units of mass per unit surface per unit time, for instance grams per square metre per day. The mass unit may relate to dry matter or to the mass of carbon generated...
, which would make its population more resilient to fishing pressure. This species is not targeted commercially
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...
, but is probably taken 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 inshore fisheries throughout its range. It is also harvested for the home aquarium trade
Fishkeeping
Fishkeeping is a popular hobby concerned with keeping fish in a home aquarium or garden pond. There is also a fishkeeping industry, as a branch of agriculture.-Types of fishkeeping systems:...
, being the most frequently available member of its family on the North American market. The extent of this trade has not yet been quantified. Another potential threat is habitat degradation, particularly to seagrass beds. No conservation measures have been enacted for this species.