Stingray

Stingrays Temporal range: Early Cretaceous to recent[1] PreꞒ Ꞓ O S D C P T J K Pg N
Southern stingray (Hypanus americanus)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Superorder:	Batoidea
Order:	Myliobatiformes
Suborder:	Myliobatoidei Compagno , 1973
Families
Hexatrygonoidea Hexatrygonidae Urolophoidea Plesiobatidae Urolophidae Dasyatoidea Urotrygonidae Dasyatidae Potamotrygonidae Gymnuridae † Dasyomyliobatidae Myliobatidae †Rhombodontidae

Stingrays are a group of sea

There are about 220 known stingray species organized into 29 genera.

Stingrays are common in coastal

Stingray species are

Evolution

Heliobatis radians

Stingrays diverged from their closest relatives, the panrays, during the Late Jurassic period, and diversified over the course of the Cretaceous into the different extant families today. The earliest stingrays appear to have been benthic, with the ancestors of the eagle rays becoming pelagic during the early Late Cretaceous.^[7][8]

Fossils

Full-body stingray fossils are very rare but are known from certain lagerstätte that preserve soft-bodied animals. The extinct Cyclobatis of the Cretaceous of Lebanon is thought to be a skate that had convergently evolved a highly stingray-like body plan, although its exact taxonomic placement is still uncertain.^[10] True stingray fossils become more common in the Eocene, with the extinct freshwater stingrays Heliobatis and Asterotrygon known from the Green River Formation.^[11] A diversity of stingray fossils is known from the Eocene Monte Bolca formation from Italy, including the early stingaree Arechia, as well as Dasyomyliobatis, which is thought to represent a transitional form between stingrays and eagle rays, and the highly unusual Lessiniabatis, which had an extremely short and slender tail with no sting.^[7][8]

Anatomy

Jaw and teeth

The mouth of the stingray is located on the

Spiracles

Spiracles are small openings that allow some fish and amphibians to breathe. Stingray spiracles are openings just behind its eyes. The respiratory system of stingrays is complicated by having two separate ways to take in water to use the oxygen. Most of the time stingrays take in water using their mouth and then send the water through the gills for gas exchange. This is efficient, but the mouth cannot be used when hunting because the stingrays bury themselves in the ocean sediment and wait for prey to swim by.^[16] So the stingray switches to using its spiracles. With the spiracles, they can draw water free from sediment directly into their gills for gas exchange.^[17] These alternate ventilation organs are less efficient than the mouth, since spiracles are unable to pull the same volume of water. However, it is enough when the stingray is quietly waiting to ambush its prey.

The flattened bodies of stingrays allow them to effectively conceal themselves in their environments. Stingrays do this by agitating the sand and hiding beneath it. Because their eyes are on top of their bodies and their mouths on the undersides, stingrays cannot see their prey after capture; instead, they use smell and electroreceptors (ampullae of Lorenzini) similar to those of sharks.^[18] Stingrays settle on the bottom while feeding, often leaving only their eyes and tails visible. Coral reefs are favorite feeding grounds and are usually shared with sharks during high tide.^[19]

Behavior

Reproduction

During the

Reproductive ray behaviors are associated with their behavioral endocrinology, for example, in species such as the atlantic stingray (Hypanus sabinus), social groups are formed first, then the sexes display complex courtship behaviors that end in pair copulation which is similar to the species Urobatis halleri.^[22] Furthermore, their mating period is one of the longest recorded in elasmobranch fish. Individuals are known to mate for seven months before the females ovulate in March. During this time, the male stingrays experience increased levels of androgen hormones which has been linked to its prolonged mating periods.^[22] The behavior expressed among males and females during specific parts of this period involves aggressive social interactions.^[22] Frequently, the males trail females with their snout near the female vent then proceed to bite the female on her fins and her body.^[22] Although this mating behavior is similar to the species Urobatis halleri, differences can be seen in the particular actions of Hypanus sabinus. Seasonal elevated levels of serum androgens coincide with the expressed aggressive behavior, which led to the proposal that androgen steroids start, indorse and maintain aggressive sexual behaviors in the male rays for this species which drives the prolonged mating season. Similarly, concise elevations of serum androgens in females has been connected to increased aggression and improvement in mate choice. When their androgen steroid levels are elevated, they are able to improve their mate choice by quickly fleeing from tenacious males when undergoing ovulation succeeding impregnation. This ability affects the paternity of their offspring by refusing less qualified mates.^[22]

Stingrays are

At the Sea Life London Aquarium, two female stingrays delivered seven baby stingrays, although the mothers have not been near a male for two years. This suggests some species of rays can store sperm then give birth when they deem conditions to be suitable.^[25]

Locomotion

The stingray uses its paired

Feeding behavior and diet

Stingrays use a wide range of feeding strategies. Some have specialized jaws that allow them to crush hard mollusk shells,

performed by ray-finned fish. Stingrays exhibit a wide range of colors and patterns on their dorsal surface to help them camouflage with the sandy bottom. Some stingrays can even change color over the course of several days to adjust to new habitats. Since their mouths are on the underside of their bodies, they catch their prey, then crush and eat with their powerful jaws. Like its shark relatives, the stingray is outfitted with electrical sensors called ampullae of Lorenzini. Located around the stingray's mouth, these organs sense the natural electrical charges of potential prey. Many rays have jaw teeth to enable them to crush mollusks such as clams, oysters and mussels.

Most stingrays feed primarily on mollusks, crustaceans and, occasionally, on small fish. Freshwater stingrays in the Amazon feed on insects and break down their tough exoskeletons with mammal-like chewing motions.^[34] Large pelagic rays like the manta use ram feeding to consume vast quantities of plankton and have been seen swimming in acrobatic patterns through plankton patches.^[35]

Stingray injuries

Stingrays are not usually aggressive and ordinarily attack humans only when provoked, such as when they are accidentally stepped on.^[36] Stingrays can have one, two or three blades. Contact with the spinal blade or blades causes local trauma (from the cut itself), pain, swelling, muscle cramps from the venom and, later, may result in infection from bacteria or fungi.^[37] The injury is very painful, but rarely life-threatening unless the stinger pierces a vital area.^[36] The blade is often deeply barbed and usually breaks off in the wound. Surgery may be required to remove the fragments.^[38]

Fatal stings are very rare.^[36] The death of Steve Irwin in 2006 was only the second recorded in Australian waters since 1945.^[39] The stinger penetrated his thoracic wall and pierced his heart, causing massive trauma and bleeding.^[40]

Venom

The venom of the stingray has been relatively unstudied due to the mixture of venomous tissue secretions cells and mucous membrane cell products that occurs upon secretion from the spinal blade. The spine is covered with the epidermal skin layer. During secretion, the venom penetrates the epidermis and mixes with the mucus to release the venom on its victim. Typically, other venomous organisms create and store their venom in a gland. The stingray is notable in that it stores its venom within tissue cells. The toxins that have been confirmed to be within the venom are cystatins, peroxiredoxin and galectin.^[41] Galectin induces cell death in its victims and cystatins inhibit defense enzymes. In humans, these toxins lead to increased blood flow in the superficial capillaries and cell death.^[42] Despite the number of cells and toxins that are within the stingray, there is little relative energy required to produce and store the venom.

The venom is produced and stored in the secretory cells of the vertebral column at the mid-distal region. These secretory cells are housed within the ventrolateral grooves of the spine. The cells of both marine and freshwater stingrays are round and contain a great amount of granule-filled cytoplasm.^[43] The stinging cells of marine stingrays are located only within these lateral grooves of the stinger.^[44] The stinging cells of freshwater stingray branch out beyond the lateral grooves to cover a larger surface area along the entire blade. Due to this large area and an increased number of proteins within the cells, the venom of freshwater stingrays has a greater toxicity than that of marine stingrays.^[43]

Human use

As food

Rays are edible, and may be caught as food using fishing lines or spears. Stingray recipes can be found in many coastal areas worldwide.^[45] For example, in Malaysia and Singapore, stingray is commonly grilled over charcoal, then served with spicy sambal sauce. In Goa, and other Indian states, it is sometimes used as part of spicy curries. Generally, the most prized parts of the stingray are the wings, the "cheek" (the area surrounding the eyes), and the liver. The rest of the ray is considered too rubbery to have any culinary uses.^[46]

Ecotourism

Stingray City in the Cayman Islands

.

Stingrays are usually very docile and curious, their usual reaction being to flee any disturbance, but they sometimes brush their fins past any new object they encounter. Nevertheless, certain larger species may be more aggressive and should be approached with caution, as the stingray's defensive reflex (use of its venomous stinger) may result in serious injury or death.[47]

Other uses

The skin of the ray is used as an under layer for the cord or leather wrap (known as samegawa in

Several ethnological sections in museums,[49] such as the British Museum, display arrowheads and spearheads made of stingray stingers, used in Micronesia and elsewhere.^[50] Henry de Monfreid stated in his books that before World War II, in the Horn of Africa, whips were made from the tails of big stingrays and these devices inflicted cruel cuts, so in Aden, the British forbade their use on women and slaves. In former Spanish colonies, a stingray is called raya látigo ("whip ray").

Some stingray species are commonly seen in public aquarium exhibits and more recently in home aquaria.^[45][51]

Gallery

• 
  Unlike other

  gill slits

  .
• 
  Deepwater stingrays (Plesiobatis daviesi) are found on the upper continental slope throughout the Indo-Pacific.
• 
  Spotted stingarees (Urolophus gigas) are found along the Western Australian coast.
• 
  Western American

  coast.
• 
  Leopard whiprays (Himantura leoparda) are vulnerable from overfishing.
• 
  freshwater environments along the Southeastern United States

  coast.
• 
  The smalleye stingray (Megatrygon microps) is a rare stingray distributed throughout the Indo-Pacific.
• 
  The

  open ocean

  .
• 
  Bluespotted ribbontail rays (Taeniura lymma) are near threatened.
• 
  Giant freshwater stingrays (Urogymnus polylepis) are the largest freshwater fish.
• 
  South American

  rivers.
• 
  South American

  coast.
• 
  Bull rays (Aetomylaeus bovinus) are found along European and African coasts.
• 
  Giant oceanic manta rays (Mobula birostris) are the largest of the stingrays.
• 
  Golden cownose rays (Rhinoptera steindachneri) often migrate in large schools.

See also

• List of threatened rays

References

Bibliography

• Froese, Rainer, and Daniel Pauly, eds. (2005). "Dasyatidae" in FishBase. August 2005 version.

External links

Wikimedia Commons has media related to Stingray.

• "Beware the Ugly Sting Ray." Popular Science, July 1954, pp. 117–118/pp. 224–228.