General information about Stingray.

Introduction.



Stingrays are a part of the shark family known as Dasyatidae. They are common in most tropical and subtropical ocean around the world. There are many types of stingrays around the world. Some live in warmer temperature oceans like the Dasyatis thetidis and some species live entirely in freshwater rivers for example the Dasyatis Laosensis and Himantura chaophraya.
While most species of stingrays live in areas that are not threatened, there are a few species, such as the Dasyatis Laosensis are facing problematic conservation. Hence making them to be listed as endangered species.





Characteristics.


The stingrays can be found in almost any major ocean in the world such as Atlantic, Indian, pacific oceans. Most stingrays are marines and live in salt water but they could also be found in fresh water and where there’s a mixture of fresh and salt water called brackish water. Stingrays breathe through the small holes behind eyes by drawing in the water. Most stingrays are ovoviviparous where the embryo is contained in a membranous egg case, once it has hatch the rays stacks in the oviduct until fully developed. Stingrays are capable to bear up to five to thirteen liters of offspring. As the embryo are in development it feeds of the nutrient from the membranous egg case.
As defensive mechanism the rays has a barbed tail or stingers at the end of their tails. The stinger is a modified dermal denticle that is able to penetrate into the predators hide. Stingrays are usually docile unless threaten. Most injuries inflicted on human are usually on the ankle or calves as humans accidentally step on them. When do so the rays flick its tail in front and stabs the victim. The stinger is compose of the enzymes 5-nucleotidase and phosphodiesterase and the neurotransmitter serotonin. It is a type of venom that cause smooth muscle to severely contract and inflict pain.
Stingrays have flatten bodies so that it can conceal itself in their envoriment.it also acts as a defensive mechanism to prevent being eaten by other predators like sharks and larger fishes. It also helps them to prey on smaller fishes and shrimps. They use their strong semse of smell and highly sensitive electro-receptors to detect their prey. Some stingray’s mouth contains hard, powerful, shell-crushing plates, while others species have sucking mouthparts. Stingrays settle on the bottom to feed. The best place for them to feed are coral reefs.















Stingrays have flatten bodies so that it can conceal itself in their environment it also acts as a defensive mechanism to prevent being eaten by other predators like sharks and larger fishes. It also helps them to prey on smaller fishes and shrimps. They use their strong sense of smell and highly sensitive electro-receptors to detect their prey. Some stingray’s mouth contains hard, powerful, shell-crushing plates, while others species have sucking mouthparts. Stingrays settle on the bottom to feed. The best place for them to feed are coral reefs.
























Eco-tourism.



Stingrays are very shy and curious animals. Normally they will flee away from any disturbance, thinking that it is a threat to them. But sometimes they will brush their fins pass any object out of curiosity. However, certain larger species are usually more aggressive and must be approached with caution by humans, as their reflexes may result in serious injury or even death. Recently an Australian zoologist name Steve Irwin lost his life when a giant stingray stab through his heart with its stingers. Since then, divers and marine zoologists are more aware of the aggressiveness and the power of stingrays.
Stingrays are not normally visible to swimmers. But divers and snorkelers are able to see them in shallow waters when the water in warm. In the Cayman Islands there are several dive sites called Stingray City, Grand Cayman, where divers and snorkelers can swim with the large southern stingrays and watch professional divers feed the stingrays by hand.

Various type of Stingray.

Whipray (Himantura chaophraya)

Inhabits sandy bottoms in estuaries and large rivers. Feeds on benthic invertebrates and fishes. Ovoviviparous. Caught occasionally by demersal gillnet and longline fisheries operating in riverine and estuarine areas. Utilized for its meat and possibly its cartilage. Marketed fresh, with large individuals being sold in cut pieces by the kilogram. Size reaches to about 500 cm long. Threatened due to over harvesting and pollution. It is distributed around Asia and Oceania: Mekong and Chao Phraya basins; also from eastern Borneo, New Guinea and northern Australia.

Bluespotted stingray (Neotrygon kuhlii)

A solitary species found on sandy bottoms near rocky or coral reefs. Usually found in deeper water but moves onto the reef flat and into shallow lagoons at high tide. Occasionally covers itself with sand, leaving only its eyes and tail visible. Feeds on crabs and shrimps. Ovoviviparous. The venomous spine can inflict a painful wound. Caught in very large quantities in the bottom trawl, trammel and fish trap fisheries. Utilized for its meat but of limited value due to its small size. It's distribution is across Indo-West Pacific: Red Sea and East Africa to Samoa and Tonga, north to Japan, south to Australia. Represented by multiple color morphs in the Indo-Pacific which may be different species.

Cowtail Stingray (Pastinachus sephen)

The Cowtail Stingray gets it's name form it's thick broad tail trunk. It's common inshore in tyropical seas, venturing into estuaries and sometimes freshwater. They tend to be inquisitive and approach closely if fish have been speared. It has also been called the Banana-tail Ray, Fantail Ray, Feathertail Stingray, Guergunna and Weralli. The Cowtail Stingray has a disc that is slightly wider than long. It has small eyes and a very wide interorbital space. The tail is about twice the length of the disc. The upper surface of the disc is a uniform grey, brown or black. The lower surface is white. The tail is depressed basally becoming more cylindrical distally. The broad skin flap and tip of the tail are black. It is mainly distributed in tropical marine waters of the Indo-West Pacific. In Australia it is known from the central coast of Western Australia, around the tropical north of the country and south to the central coast of New South Wales.

Pelagic stingray (Pteroplatytrygon violacea)

A thick, dark stingray with a broadly rounded snout and an angular pectoral disc; tail less than twice body length with a long lower caudal finfold ending far in front of tail tip, but with no upper finfold; disc without thorns; usually 1 extremely long sting on tail; eyes do not protrude. Uniformly violet, purple, or dark blue-green dorsally and ventrally. No prominent markings. It is mainly distributed in tropical and subtropical seas. Eastern Atlantic: southeastern coasts of the Mediterranean and off Sicily. Reported from Cape Verde. Eastern Pacific: California (USA), Baja California (Mexico), and the Galapagos Islands Reported off Vancouver and from Chile. Western Atlantic. There are 4 records from southern Africa.

Porcupine ray (Urogymnus asperrimus )

A heavily armored stingray lacking a venomous barb; young with large, flat denticles on upper surface, and large juveniles and adults with additional sharp conical thorns and small, pointed denticles. Very thick elongated disc with broadly rounded outer corners; snout broadly rounded and tail slender, about as long as body and without finfolds. Light grey or whitish dorsally, white ventrally; tail blackish. It is mainly distributed across Indo-Pacific: Red Sea and coast of East Africa to the Marshall Islands and Fiji, south to northern Australia. Eastern Atlantic: Senegal, Guinea, and Côte d'Ivoire.