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Stingray

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For other uses, see the family of marine fish.

Stingrays
Temporal range: Late Cretaceous–Recent[1]
Southern stingray, Dasyatis americana
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Chondrichthyes
Subclass:
Elasmobranchii
Order:
Rajiformes
Family:
Dasyatidae
Genera

Dasyatis
Himantura
Pastinachus
Pteroplatytrygon
Taeniura
Urogymnus

The stingrays are a family—Dasyatidae—of rays, cartilaginous fishes related to sharks. They are common in coastal tropical and subtropical marine waters throughout the world, but the family also includes species found in warmer temperate oceans such as Dasyatis thetidis, and species entirely restricted to fresh water such as D. laosensis and Himantura chaophraya. With the exception of Pteroplatytrygon violacea, all dasyatids are demersal.[2]

They are named after the barbed stinger (actually a modified dermal denticle) on their tail, which is used exclusively in self-defense (they are also known colloquially as "Irwin Killers" in some circles[3]). The stinger may reach a length of approximately 35 cm, and its underside has two grooves with venom glands.[4] The stinger is covered with a thin layer of skin, the integumentary sheath, in which the venom is concentrated.[5] Some species have several stingers, and a few, notably Urogymnus asperrimus, lack a sting entirely.[6]

Other types of rays also referred to as "stingrays" are the river stingrays (family Potamotrygonidae), the round stingrays (families Urolophidae and Urotrygonidae), the sixgill stingray (family Hexatrygonidae), and the deepwater stingray (family Plesiobatidae). For clarity, the members of the family Dasyatidae are sometimes called whip-tail stingrays.[7]

While most dasyatids are relatively widespread and not currently threatened, there are several species (for example Taeniura meyeni, D. colarensis, D. garouaensis, and D. laosensis) where the conservation status is more problematic, leading to them being listed as vulnerable or endangered by IUCN. The status of several other species are poorly known, leading to them being listed as Data Deficient.[8]

Behavior

Feeding

A stingray's underside showing its mouth and the double row of gill openings. The two claspers (at the base of the tail) identifies it as male.

The flattened bodies of stingrays allow them to effectively conceal themselves in their environment. 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; instead, they use smell and electro-receptors (ampullae of Lorenzini) similar to those of sharks. Stingrays feed primarily on mollusks, crustaceans, and occasionally on small fish. Some stingrays' mouths contain two powerful, shell-crushing plates, while other species only have sucking mouthparts. Stingrays settle on the bottom while feeding, often leaving only their eyes and tail visible. Coral reefs are favorite feeding grounds and are usually shared with sharks during high tide.

Reproduction

When a male is courting a female, he will follow her closely, biting at her pectoral disc.

Stingrays are ovoviviparous, bearing live young in "litters" of five to thirteen. The female holds the embryos in the womb without a placenta. Instead, the embryos absorb nutrients from a yolk sac, and after the sac is depleted, the mother provides uterine "milk".[9]

Stingray injuries

The single stinger of H. granulata is placed on the first third of the tail.
A stingray's stinger next to a ruler (in centimetre).

Dasyatids generally do not attack aggressively or even actively defend themselves. When threatened, their primary reaction is to swim away. However, when attacked by predators or stepped on, the stinger in their tail is whipped up. This is normally ineffective against sharks, their main predator.[10]

Depending on the size of the stingray, humans are usually stung in the lower limb region. Stings usually occur when swimmers or divers accidentally step on a stingray,[11] but a human is less likely to be stung by simply brushing against the stinger. Surfers and those who enter waters with large populations of stingrays have learned to slide their feet through the sand rather than taking steps, as the rays detect this and swim away. Stamping hard on the bottom as one treads through murky water will also cause them to swim away. Humans who harass stingrays have been known to be stung elsewhere, sometimes leading to fatalities. The stinger usually breaks off in the wound. This is not fatal to the stingray as it will be regrown at a rate of about 1.25 to 2 centimetres (0.49 to 0.79 in) per month (though with significant variations depending on the size of the stingray and the exact species). Contact with the stinger causes local trauma (from the cut itself), pain, swelling, and muscle cramps from the venom, and possible later infection from bacteria.[11] Immediate injuries to humans include, but are not limited to: poisoning, punctures, severed arteries, and sometimes death.[12] Fatal stings are very rare, but can happen,[11] famously including Steve Irwin.[13]

Treatment for stings may include application of hot water (optimum temperature is 45 °C (113 °F), taking care not to cause thermal burns),[11] which can help ease pain by denaturing the complex venom protein, and antibiotics. Immediate injection of a local anesthetic in and around the wound, or a regional nerve blockade, can be helpful, as can the use of parenteral opiates such as intramuscular pethidine.[11] Local anesthetic may bring almost instant relief for several hours. Vinegar and papain are ineffective. Pain normally lasts up to 48 hours, but is most severe in the first 30–60 minutes and may be accompanied by nausea, fatigue, headaches, fever, and chills. All stingray injuries should be medically assessed;[11] the wound must be thoroughly cleaned, and surgical exploration is often required to remove any barb fragments remaining in the wound. Following cleaning, an ultrasound is helpful to confirm removal of all the barb fragments.[14] Not all remnants are radio-opaque; but x-ray radiography imaging may be helpful where ultrasound is not available.[11]

As food

Barbecued stingray is commonly served in Singapore and Malaysia.

Rays are edible, and may also be caught as food by fishing lines or spears. Stingray recipes abound throughout the world, with dried forms of the wings being most common. For example, in Singapore and Malaysia, stingray is commonly barbecued over charcoal, then served with spicy sambal sauce. 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.

While not independently valuable as a food source, the stingray's capacity to damage shell fishing grounds can lead to bounties being placed on their removal.

Eco-tourism

Stingray City in Grand Cayman allows swimmers, snorkelers, and divers to swim with and feed the stingrays.

Stingrays are usually very docile and curious, their usual reaction being to flee any disturbance. Nevertheless, certain larger species may be more aggressive and should only be approached with caution by humans, as the stingray's defensive reflex may result in serious injury or death.

Dasyatids are not normally visible to swimmers, but divers and snorkelers may find them in shallow sandy waters, more so when the water is warm. In the Cayman Islands there are several dive sites called Stingray City, Grand Cayman, where divers and snorkelers can swim with large southern stingrays (D. americana) and watch while professional scuba instructors feed them by hand. There is also a "Stingray City" in the sea surrounding the Caribbean island of Antigua. It consists of a large, shallow reserve where the rays live, and snorkeling is possible.

In Belize off the island of Ambergris Caye there is a popular marine sanctuary called Hol Chan. Here, divers and snorkelers often gather to watch stingrays and nurse sharks that are drawn to the area by tour operators who feed the animals.

Many Tahitian island resorts regularly offer guests the chance to "feed the stingrays and sharks". This consists of taking a boat to the outer lagoon reefs then standing in waist-high water while habituated stingrays swarm around, pressing right up against tourists seeking food from their hands or that being tossed into the water. The boat owners also "call in" sharks which, when they arrive from the ocean, swoop through the shallow water above the reef and snatch food offered to them.

Other uses

The skin of the ray (same) is used as an under layer for the cord or leather wrap (ito) on Japanese swords (katanas) due to its hard, rough, texture that keeps the braided wrap from sliding on the handle during use. They are also used to make exotic shoes. They are used to make boots, belts, wallets, jackets, and even cellphone cases.[15]

Species

An Atlantic stingray
A thorntail stingray

There are about seventy species in seven genera:

A Himantura stingray

See also

References

  1. ^ Froese, Rainer; Pauly, Daniel (eds.). "Family Dasyatidae". FishBase. January 2009 version.
  2. ^ Bester, C., H. F. Mollett, & J. Bourdon. "Pelagic Stingray". Florida Museum of Natural History, Ichthyology department. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)CS1 maint: multiple names: authors list (link)
  3. ^ http://en.wikipedia.org/wiki/Steve_irwin#Death
  4. ^ Ternay, A. "Dangerous and Venomous Aquarium Fish" (PDF). fishchannel.com. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  5. ^ Meyer, P. (1997). "Stingray injuries". Wilderness Environ Med. 8 (1): 24–8. PMID 11990133.
  6. ^ Froese, Rainer; Pauly, Daniel (eds.). "Urogymnus asperrimus". FishBase. September 2009 version.
  7. ^ Debelius, H. (1993). Indian Ocean Tropical Fish Guide. Aquaprint Verlags GmbH. ISBN 3-927991-01-5.
  8. ^ "IUCN Red List". International Union for Conservation of Nature. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  9. ^ Florida Museum of Natural History Ichthyology Department: Atlantic Stingray
  10. ^ "Stingray City - About Stingrays". Caribbean Magazine.
  11. ^ a b c d e f g Slaughter RJ, Beasley DM, Lambie BS, Schep LJ (2009). "New Zealand's venomous creatures". N Z Med J. 122 (1290): 83–97. PMID 19319171.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  12. ^ Taylor, G. (2000). "Toxic fish spine injury: Lessons from 11 years experience". South Pacific Underwater Medicine Society journal. 30 (1). ISSN 0813-1988. OCLC 16986801. Retrieved 2008-06-15.[dead link]
  13. ^ Discovery Channel Mourns the Death of Steve Irwin
  14. ^ Flint D, Sugrue W (1999). "Stingray injuries: a lesson in debridement". N Z Med J. 112 (1086): 137–8. PMID 10340692.
  15. ^ [1]
  16. ^ Last, Manjaji-Matsumoto & Kailola (2006). "Himantura hortlei n. sp., a new species of whipray (Myliobatiformes: Dasyatidae) from Irian Jaya, Indonesia" (PDF). Zootaxa. 1239: 19–34.
  17. ^ Manjaji-Matsumoto & Last (2006). "Himantura lobistoma, a new whipray (Rajiformes: Dasyatidae) from Borneo, with comments on the status of Dasyatis microphthalmus". Ichthyological Research. 53 (3): 291ff. doi:10.1007/s10228-006-0350-6.
  18. ^ Roberts (2006). "Makararaja chindwinensis, a new genus and species of freshwater dasyatidid stingray from upper Myanmar". The Natural History Bulletin of the Siam Society. 54: 285–293.
  19. ^ Last, Manjaji & Yearsley (2005). "Pastinachus solocirostris sp. nov., a new species of Stingray (Elasmobranchii: Myliobatiformes) from the Indo-Malay Archipelago" (PDF). Zootaxa. 1040: 1–16.

Bibliography

Wikimedia Commons has media related to Dasyatidae.
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