Tag Archive: Elasmobranchs


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
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.

3300565561_c2b08f97ab_b

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

3300566493_c6e0f406ba_b

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

%d bloggers like this: