Tag Archive: Cartilaginous fishes

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.


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

Kingdom: Animalia
Phylum: Chordata
Class: Elasmobranchii (sharks and rays)
Order: Carcharhiniformes (Ground sharks; characterized by the presence of a nictitating membrane over the eye, two dorsal fins, an anal fin, and five gill slits.)
Family: Scyliorhinidae (Cat sharks; elongated cat-like eyes and a patterned appearance, ranging from stripes to patches to spots)

Genus/species: Cephaloscyllium ventriosum


GENERAL CHARACTERISTICS: Swell sharks have a stout body with flat, broad head; short snout; huge mouth,  proportionally larger that the great white shark (Carcharodon carcharias). Teeth are at front of jaws with dagger-like central point and 1-2 small points on each side; two dorsal fins: first much larger, with origin over pelvic fins, second dorsal fin considerably smaller than first, its origin over origin of anal fin. The body is light brown with dark patches covered with black dots.

Length up to 3.2 ft.

DISTRIBUTION/HABITAT: Central California to southern Mexico; also reported near central Chile.
Found in rocky reefs and kelp forests, from surface to 460 m (1500 ft), in temperate and subtropical waters.

Swell Shark 3426936973_ee6379d9fb_b

DIET IN THE WILD: C. ventriosum is nocturnal; feeding on crustaceans and fishes, (often blacksmiths). They are lie-in-wait predators that sit on the bottom with wide-open mouth, ready to ambush unsuspecting prey. (slowly opens jaws; lies in wait for prey to swim inside).

egg case above

REPRODUCTION: Oviparous; female lays amber-colored egg cases that hatch in 8–10 months. Egg case (“mermaid’s purse”) is 9 – 13 centimeters (3.5 – 5 inches) long, 3 – 6 centimeters (1 – 2.3 inches) wide. Young have enlarged toothlike denticles on the back that help them break through egg cases. Pups measure 14 – 15 centimeters (5.5-6 in) at birth; immediately feed on their own.

Embryos may be eaten by snails that bore through egg cases.

Pup  below on top of egg case

PREDATORS:  If caught it is, usually it will be released because its flesh is of poor quality.    Life span: 25 or more years.

CONSERVATION: IUCN Red List: least concern species

REMARKS: C. ventriosum hides in caves and crevices during normal aquarium hours. the day, and so is often not to be seen during aquarium hours. Common and specific (ventriosum = “largebelly”) names come from its ability to take in water that makes it appear up to twice as large as its normal size, a difficult meal for predators to bite or to remove from a crevice. If caught and brought to the surface, it can swell its body with air.

When caught by fishermen and brought out of water, the release of gulped water/air can cause the swell shark to “bark”.

Occurs in aggregations while resting, sometimes piled one on top of the other.

Southern California Coast Kelp Exhibit Tidepool young with egg cases.


California Academy of Sciences Steinhart Aquarium Southern California Coast Kelp Exhibit 2018

Ron’s WordPress shortlink wp.me/p1DZ4b-XL

Ron’s flickr 7608440813109/www.flickr.com/photos/cas_docents/14479061579/in/set-7215

fishbase www.fishbase.org/summary/802

Marine bio.org marinebio.org/species.asp?id=383

 eol eol.org/pages/208742/details

Sean Donahoe, CAS docent, materials from the Naturalist Center and collaborated with Docent Program staff document.

Works Cited

1. Carwardine, M. 2004. Shark. Firefly Books. Buffalo. 168 p.

2. Michael, S.W. 1993. Reef Sharks and Rays of the World: A guide to their

identification, behavior, and ecology. Sea Challengers. Monterey. 107 p.

3. Parker, S. and Parker, J. 1999. The Encyclopedia of Sharks. Firefly Books.

Buffalo. 192 p.

4. Ebert, D.A. 2003. Sharks, Rays, and Chimeras of California. University of

California Press. Berkeley/Los Angeles. 284 p.

5. Springer, V.G. and Gold, J.P. 1989. Sharks in Question. Smithsonian Institution

Press. Washington, D.C. 187 p.



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


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.


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.


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/


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.


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


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.


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

Class: Actinopterygii (ray-finned fishes)
Order: Acipenseriformes (Sturgeons and paddlefishes)
Family:Polyodontidae Paddlefishes (Paddlefishes)

Genus/species: Polyodon spathula

GENERAL CHARACTERISTICS: Gray, shark-like body with a deeply forked tail and huge toothless mouth when feeding. Extended upper jaw (rostrum) flattened into paddleshape, accounts for 1/3 of total body length. Fins stiffer than those of teleost fishes. Heterocercal tail. Skeleton cartilaginous, skin tough, scales lacking. Max length 221 cm (87 inches); max weight 90.7 kg (200 pounds), average weight considerably less.

DISTRIBUTION/HABITAT: Rivers of central United States, especially Mississippi River and its tributaries. Prefers deep pools in large rivers where the current is slow; is highly mobile and has been known to travel more than 2,000 miles.


DIET IN THE WILD: Zooplankton, the majority being water fleas, also tiny crustaceans and larvae. To feed, the fish swims with its huge mouth wide open. As the water passes over its gills food is filtered out by special filaments called gill rakers. Also, the paddle is covered with pores that extend over the head and along the gill covers. These pores are electroreceptors capable of detecting as little as 1/100 of 1-millionth volt per cm, enough to sense the presence of plankton, a valuable tool, especially since vision, hearing and smell are poor.

REPRODUCTION and DEVELOPMENT: Female spawn only once every 4 to 7 years starting when they are 6-12 years old swimming up river to lay 2 eggs at a time. Egg cases rounded. Eggs hatch in 7 days; young are swept downstream to permanent home.

MORTALITY: Live up to 30 years.

PREDATORS: Only man.

CONSERVATION STATUS: IUCN: vulnerable. Threatened by overfishing throughout much of its range, particularly for its eggs since the ban on imported caviar. Dams prevent fish from reaching spawning grounds, sedimentation and river modifications destroy habitat.

Mississippi paddlefish   (Polyodon spathula)  IMG_2499 - Version 2

REMARKS: The paddle is covered with pores that extend over the head and along the gill covers. These pores are electroreceptors capable of detecting as little as 1/100 of 1-millionth volt per cm, enough to sense the presence of plankton, a valuable tool, especially since vision, hearing and smell are poor.

Both paddlefish and sharks have skeletons made of cartilage, not bone. Paddlefish have no scales.

Paddlefish are the oldest surviving animal species in North America. Fossil records indicate that they date back 300 million years.

Water Planet Feeding Cluster WP31

Ron’s flickr  http://www.flickr.com/photos/cas_docents/sets/72157625017923579/with/3186623140/

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

Kingdom: Animalia
Phylum: Chordata
Class Actinopterygii (ray-finned fishes) 
Order Acipenseriformes (Sturgeons and paddlefishes)
Family  Acipenseridae (Sturgeons)

Genus/species: Scaphirhynchus albus 

GENERAL CHARACTERISTICS: Shark-like with heterocercal tale and scutes instead of scales; gray above, white below. Flat, upturned head. Four long barbels. One of the rarest and largest freshwater fishes in North America; length to over 2 m (6.5 feet), weight over 75 lbs.

Pallid Sturgeon  8395624080_f62868641d_b

DISTRIBUTION/HABITAT: Missouri and Mississippi Rivers and their large tributaries, especially the Kansas River, from Montana to the Gulf
of Mexico. Found on the bottom in turbid, deep, fast
 flowing rivers over sand and gravel bars. 

DIET: Mollusks, insects, and small fishes. S. albus  is a bottom feeder. In addition to taste buds on the tips of the barbels it has sensory organs on the ventral surface of the
snout that pick up electrical fields emanating from prey. The sturgeon stirs up the muck with its snout, then the mouth, which is folded in.

REPRODUCTION and DEVELOPMENT: In the wild, external fertilization, eggs scattered and not guarded. However, natural reproduction is almost non-existent. Since 1990 over 150,000 pallid sturgeon have been raised in hatcheries and released.

MORTALITY/LONGEVITY: Life span: up to 50 years or more.

CONSERVATION STATUS:: ESA: federally listed 1990: Endangered.Our juvenile pallids came from Gavin’s Point National Fish Hatchery in Montana. The Steinhart is permitted to display these 88 A Docent & Guide View of the Steinhart Aquarium Species
endangered species as long as an educational message is presented about their distribution, endangered status, and threats facing them.

REMARKS: Pallid and shovelnose sturgeon are
 known to hybridize, another potential threat to the species survival in the southern portion of the pallid’s range where shovel nose sturgeon dominate. Often referred to as the Dinosaur of the Missouri, the pallid sturgeon is known from 70 million years ago and at one time was the top freshwater carnivore. Like all sturgeon, have a cartilaginous skeleton.

Water Planet, Feeding Cluster WP31 

flickr http://www.flickr.com/photos/cas_docents/sets/72157608608528651/with/8395624080/

WordPress Shortlink http://wp.me/p1DZ4b-kX

Raja binoculata  Class Chondrichthyes, Subclass Elasmobranchii (sharks and rays), Order Rajiformes (Skates and rays), Family Rajidae (Skates).

DISTRIBUTION: Bering Sea and southeastern Alaska to central Baja California.

HABITAT: Bottom dwellers on soft substrates, usually from shallow water to 300 m.  Found along the coast in estuaries, bays, and over the continental shelf. 

APPEARANCE:  Largest species of skate, adults usually 1.8 m (5.9 ft) and 91 kg (200 lb). There are two large dark spots with pale borders, one on each wing. The ventral side is white, sometimes with dark spots or blotches.

DIET: Benthic shrimps, worms, clams, some fishes.

REPRODUCTION and Development: Oviparous, and is one of the few skate species that typically have more than one embryo within each egg capsule, commonly called “mermaid’s purses”.   The egg capsule of a big skate is the largest of any skate, measuring 23–31 cm (9–12 in) long and 11–19 cm (4–7 in) wide.  The young emerge after 9 months and measure 18–23 cm (7–9 in).

REMARKS: Commercially fished off California.   R. binoculata‘s slow reproductive rate has led it to be assessed as Near Threatened by the World Conservation Union. 

LOCATION: Salt marsh pop-up CC03

 WORDPRESS SHORTLINK   http://wp.me/p1DZ4b-ev

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