Tag Archive: rays


TAXONOMY
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes (cartilaginous fishes)
Subclass: Elasmobranchii (sharks, rays and skates)
Order: Myliobatiformes
Family: Potamotrygonidae (river stingrays)

Genus/species: Potamotrygon motoro

GENERAL CHARACTERISTICS: Orange-spot Stingrays have an oval disc, with a greyish-brown upper surface patterned with distinct yellow-orange spots, and a white underside. Like most rays, flat teeth are used to grip and crush prey that is sucked into the ventral mouth. Note periscoping eyes which protrude from sand when buried. Olfaction is a major and well-developed means of perception for these stingrays; their olfactory organs are situated in laterally placed cartilaginous capsules on the top of the head. The spine on the tip of the tail is capable of delivering a painful sting.  Rays have an accessory respiratory opening, the Spiracle which is an adapted gill slit which has migrated to the top of the stingray. When the stingray is resting on the bottom the spiracle allows them to breathe.

Length up to 1 m (3 ft.) and weight up to 15 kg (33 lb.)

 

DISTRIBUTION: South America: Uruguay, Paraná- Paraguay, Orinoco, and Amazon Basins.

HABITAT: P. motoroare found in freshwater calm waters, especially on the sandy margins of lagoons, brooks and streams. They able to tolerate only a narrow range of salinities. Lost ability to retain urea decreasing osmolarity for fresh water unlike salt water relatives.

DIET IN THE WILD: They feed mostly on benthic hard-shelled invertebrates, such as clams, mussels, and crustaceans and also on worms, insect larvae, and small fishes.

REPRODUCTION: Fertilization is internal with the male attaches himself to a female by firmly clamping his jaws onto the posterior margin of her disk, sometimes leaving prominent bite marks. Females produce eggs that hatch inside the female and are then ‘born’ live after a gestation period of no more than three months. The litter size varies, from 3 to 21 young.

LIFESPAN: Maximum of 15 years in captivity.

CONSERVATION: IUCN Red list Data Deficient (DD)

REMARKS: P. motoro is one of the seven species of this genus inhabiting southern South America.

The Operculum pupillare inside the eye which controls the amount of light entering the eye. In dim light it will retract allowing greater light in and better vision at night.

They are not dangerous unless stepped on or threatened.

Fishermen also harpoon these rays during floods when they are found resting over vegetation in shallow water. P.motoro apparently has delicious meat.

References

California Academy of Sciences Steinhart Aquarium Flooded Forest Floor 2018

Ron’s flickr river stingrays  https://freshwaterstingrays.co.uk/category/freshwater-stingray-facts/

Ron’s flickr https://www.flickr.com/photos/cas_docents/3407966512/in/album-72157608387905158/

fishbase fishbase.org/summary/Potamotrygon-motoro.html

ARKive  www.arkive.org/ocellate-river-stingray/potamotrygon-motoro/

Encyclopedia of Life eol.org/pages/205366/details

IUCN Red List  www.iucnredlist.org/details/39404/0

Ron’s WordPress shortlink  http://wp.me/p1DZ4b-1tm

TAXONOMY
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Myliobatiformes
Family:Dasyatidae Family: Dasyatidae  Whiptail Stingrays; whip-like tails, which are much longer than the disc and lack dorsaland caudal fins. They also have one or more venomous spines near the base of the tail.

Genus/species: Dasyatis kuhlii

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GENERAL/CHARACTERISTICS: Angular disc. Dorsal color reddish-brown to olive drab with blue spots and smaller black spots, ventral side white. Tail with black and white bands is about as long as the body and usually has one stinging spine.

Maximum disc width: 50 cm (20 inches).

DISTRIBUTION/ HABITAT: Tropical Indo-West Pacific from the Red Sea east to the Philippines, Japan, and south to Australia. Found on sandy bottoms near coral and rocky reefs, from intertidal zone to 50 m (160 feet). Moves onto reef flats and into shallow lagoon waters at high tide.

IMG_7261

DIET IN THE WILD: Crabs and shrimp, also small fishes.

REPRODUCTION: Ovoviviparous; eggs retained in the female’s body; embryos receive nourishment from a yolk sac.

REMARKS: The Bluespotted Whiptail Stingray is venomous tail can deliver a painful wound. Like many other rays that wound humans, it usually stings only when inadvertently stepped on: it is difficult to see in turbid waters, especially when covered by sand with only the eyes visible.

References

California Academy of Sciences Reef Lagoon 2016

Ron’s WordPress shortlink  http://wp.me/p1DZ4b-YD

Ron’s flickr https://www.flickr.com/photos/cas_docents/5035114327/in/album-72157627919810858/

TAXONOMY
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii (sharks and rays)
Order: Rajiformes (Skates and rays)
Family: Myliobatidae (Cownose and Manta Rays)

Genus/species: Rhinoptera javanica

 

GENERAL CHARACTERISTICS: R. javanica is a cartilaginous fish with bat-like, swept back pectoral fins. Double-lobed snout and indented forehead. Long, slender tail. Brown above, white below. The stinger is located at base of the tail rather than half way or more down the tail as in the whiptail rays
Width up to 1.5 m (5 ft), weight up to 45 kg (100 lbs).

Rhinoptera javanica2981790284_a7f88eab35_b

DISTRIBUTION/HABITAT: Tropical, Indo-West Pacific from South Africa north to India and possibly Thailand, Indonesia and southern China. Also in Okinawa, Ryukyu Islands.  The Javanese Cownose Ray inhabits tropical bays, estuaries, among mangroves, and near coral reefs over sand and mud bottoms. It can also tolerate brackish water.

JAVANESE COWNOSE RAY (Rhinoptera javanica) IMG_1769

DIET IN THE WILD: Feeds on clams, oysters and crustaceans. The ray sucks in sand and expels it out of its gills, blowing off sand covering its prey. (Looking for prey below)

Javanese Cownose Ray Rhinoptera javanica (Myliobatidae) eating IMG_0015

REPRODUCTION: Mating pair orient in a venter to venter position, and the male inserts one or both claspers. Ovoviviparous, 1–2 pups per litter. Females have been known to leap out of the water and slam into the surface; this action seems to be an aid in birthing.

CONSERVATION STATUS: IUCN Red List  Vulnerable

A declining population is inferred from the unregulated nature of inshore fisheries as well as small litter size.

 

REMARKS:  Like its pelagic relatives the manta and devil rays, it swims by flapping its pectoral fins like wings, enabling it to swim at greater speeds than most bottom dwelling stingrays. Sometimes these “wings” protrude above the water, bearing a frightening resemblance to a shark.

References

California Academy of Sciences Reef Lagoon 2016

ARKive www.arkive.org/javanese-cownose-ray/rhinoptera-javanica/

fishbase www.fishbase.org/summary/SpeciesSummary.php?id=7971

IUCN Red List www.iucnredlist.org/details/60129/0

Ron’s WordPress Shortlink  http://wp.me/p1DZ4b-RK

Ron’s flickr http://www.flickr.com/photos/cas_docents/sets/72157608440813109/with/2981790284/


TAXONOMY

Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii (sharks and rays)
Order: Myliobatiformes (Stingrays)
Family: Dasyatidae (Stingrays)

Genus/species: Taeniura lymma

GENERAL CHARACTERISTICS: large bright blue spots on a grey-brown to yellow, olive-green or reddish-brown oval, elongated disc with lateral blue side-stripes along the tail. The snout is rounded and angular. Disc diameter to 25 cm (9.8 inches).

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DISTRIBUTION/HABITAT: Indo-West Pacific around coral reefs and sandy bottoms to a debt of 20 meters (66 feet).

DIET IN THE WILD: Prey is often detected through electroreception, a system which senses the electrical fields produced by the prey. Within the mouth are two plates, which are used for crushing mollusks, worms, shrimps, and crabs.

Taeniura lymma9830767635_6774f7ae7d_k

REPRODUCTION: T. lymma is ovoviviparous; the egg-shell is weakly formed and young hatch inside the female; they are nourished by their yolk sac and then ‘born’ live.

PREDATION: The hammerhead shark uses the cartilaginous projections form the side of their heads to pin them down to the bottom of the substrate while taking bites from the stingray’s disc. The hammerhead is able to avoid being stung by the poisonous spines on the rays tail by pinning the stingray down.

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CONSERVATION: IUCN Red List: Near threatened

REMARKS: At the tip of the tail are two sharp venomous spines (can be regenerated) which permit this ray to strike at enemies forward of its head. Venom is produced and delivered into narrow groves running lengthwise along the underside of the stinger. The entire structure is covered by a thin layer of skin which, when broken, releases its venom into its victim.

References

California Academy of Sciences Steinhart Aquarium Reef Lagoon 2016

fishbase fishbase.org/summary/Taeniura-lymma.html

Ron’s WordPress shortlink wp.me/p1DZ4b-16f

Ron’s flickr www.flickr.com/photos/cas_docents/sets/72157608440813109/

ARKive    www.arkive.org/ribbontailed-stingray/taeniura-lymma/

 


TAXONOMY

Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Myliobatiformes
Family: Dasyatidae (Whiptail Stingrays, whip-like tails, which are much longer than the disc)

Genus/species: Himantura uarnak

 

GENERAL CHARACTERISTICS: Disc light brown above with conspicuous dark spots, white ventrally. Tail with bands of black and white, three times the body length. One tail spine. The dark spots are separated in the young ray; in the adult they become crowded together, forming the reticulated pattern from which it gets its name. Snout sharply pointed. Band of flat denticles down the back.
Width up to 2 m (6.5 ft), weigh up to 120 kg (265 lbs).

 Himantura uarnak 18366435141_1e263bfff2_k

DISTRIBUTION/HABITAT: Subtropical, Indo-West Pacific, Red Sea, to southern Africa and French Polynesia, north to Taiwan, south to Australia.

Benthic, found in surf zone, sandy beaches, sandy areas of coral reefs, shallow estuaries and lagoons, down to 90 m (295 ft). It can tolerate brackish water and in India, has been found in the fresh water of Chilka Lake and the Hoogly River, a tributary of the Ganges River.

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DIET IN THE WILD: Main foods: small fish, also bivalves crabs, shrimps, worms and jellies.

REPRODUCTION: Ovoviviparous. Embryos feeding initially on yolk, then receiving additional nourishment from the mother by indirect absorption of uterine fluid enriched with mucus, fat or protein through specialised structures

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REMARKS: Although venomous, it is a popular angling fish due to its being a powerful fighter. It is not a food fish but is used in Chinese medicine.

CONSERVATION: IUCN Red list Vulnerable (VU)

REMARKS: Since their mouths are directed downward and often placed against the sand, stingrays use their spiracles rather than their mouths for water intake.

Stingrays have a spiral valve in their intestine that increases food absorption, and lack a swim bladder.

Although venomous, it is a popular angling fish due to its being a powerful fighter. It is not a food fish but is used in Chinese medicine.

References

California Academy of Sciences, Steinhart Aquarium, Reef Lagoon 2016

Ron’s flickr http://www.flickr.com/photos/cas_docents/sets/72157627919810858/

Ron’s WordPress Shortlink  http://wp.me/p1DZ4b-P8

fishbase  www.fishbase.us/summary/5507

IUCN www.iucnredlist.org/details/161692/0

Encyclopedia of Life  eol.org/pages/1859/details

Potamotrygon sp.    Elasmobranchii (Sharks and rays) > Rajiformes (Skates and rays) > Potamotrygonidae (River stingrays) 

DISTRIBUTION: Collected in the Rio Tapajos River, Brazil.

HABITAT: The shallows of major rivers and slow-moving tributaries with substrates of mud or sand.   Lost ability to retain urea decreasing osmolarity for fresh water unlike salt water relatives.

APPEARANCE: The patterning of this “species” is highly variable, with no two examples appearing the same. Some have golden markings, while others are almost white. Similarly, the amount of darker pigmentation can also vary in both shade and coverage.

REMARKS: Consumed by native tribes of the Amazon.

Potamotrygon sp. Have a venomous barb which can cause a serious and painful wound usually in the lower leg.  (Walking with a shuffling gate in water will encourage the ray to move out of the way.)  In severe wounds symptoms may include nausea, vomiting, fainting, salivation, muscle cramps, diarrhea, seizures, shock and rarely death.  Initial treatment uses hot water to help inactivate the venom and transfer to a medical facility to clean the wound and treat symptoms.

WordPress Shortlink  http://wp.me/p1DZ4b-8i


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