A stingray is depicted with his shark friend from Little Ray & Shark Patch Things Up and displayed at 50% of viewport width.
July 2019 by V. R. Duin

FISHY FISH: WHAT ARE CARTILAGINOUS FISH?

Sometimes when we trip or fumble,
teamwork may just stop our stumble.
That's why we must always show respect
to help that comes as we least expect.
(Little Ray & Shark Patch Things Up)

Fishy Fish shows differences between stingrays and manta rays and sharks. Chondrichthyes, or cartilaginous fish, have no bones, have no swim bladders, may have no scales and may not have teeth or tongues.

Stingrays and Manta Rays and Sharks

Cartilaginous Fish? The Elasmobranchii subclass of Chondrichthyes includes rays, sharks, skates and sawfish made of cartilage. Human babies have more cartilage than adults. Over time, bone replaces some of it.


Ancient Times? Elasmobranchs date back hundreds of millions of years. Their cartilaginous endoskeletons do not fossilize like bones. Their fossilized teeth show small evolutionary changes across the ages.


Dating Game? Scientists use radiocarbon dating to estimate the age of organic matter. It measures the remaining Carbon-14, or radiocarbon, a naturally-occurring radioactive isotope. Accuracy can be within decades.


From the Same Cloth? Cartilage shapes Elasmobranchs. They have no bones to provide form. Cartilage breaks and wears out. It may not repair. Distinguishing features of each Pancake Shark make them seem unrelated.

Fishy Fish Differences

Scales?

In Full Bloom? Elasmobranchs may have no scales. Some species sport denticles, classed as placoid scales. This tooth material with enamel coating, extends from the dermal, or middle skin layer. Electric rays have no scales.


It All Stacks Up? Denticles differ among Elasmobranchs. Fish scales grow with the fish. Denticles do not grow larger after a certain size. New ones fill empty spaces. The pattern is regular in sharks, but irregular in stingrays.


Age scales? Some bony fish develop yearly scale rings, like tree trunks. Counts give rough age estimates. NOAA SWFSC researchers age Elasmobranchs by counting concentric calcified bands in the vertebra.


Right Confections? Sharklet Technologies, Inc. invented denticle-like plastic medical wraps to repel germs. The CDC warns about water contamination and waterborne illness in Healthy Pets, Healthy People.

Swim Bladders?

Stop and Sink? Manta rays, Great White, Hammerhead, Mako and Whale Sharks must keep swimming. Most fish use swim bladders for up or down movements. These gas-filled sacs also may aid survival in dirty water.


Kitchen Secrets? Elasmobranchs have no swim bladders. To make up for the absence, some sharks store fats and oils in their livers. Rays and bottom-dwelling sharks use large, flat fins to control and maintain water buoyancy.


What's Inside? The largest organ, the liver, is about a third of a shark's weight. Shark livers are harvested for the medicinal trade. Predators savor them. Orcas regularly leave liver-less Great White Shark carcasses behind.


Ancestral Lungs? It is unknown if fish swim bladders evolved from ancient lungs or evolved into lungs used for breathing air. Swim bladders have no ability to intake air or efficiently extract oxygen from it.

Respiration?

Back from the Future? Fish breathe with gills. Gill arches hold them in place. Before birth, people have gill-like parts. Amphibians, crustaceans and mollusks have gills. Land or water insects and spiders also have them.


Screen Test? Bony saltwater fish drink and leak water. It enters via their mouths and gills to keep salt concentrations balanced in blood fluids. Some bony fish excrete ammonia via special pores. Others release it through gills.


Holding Forth? Stingrays and sharks neither drink nor leak water. This vital liquid comes from their food. Cartilaginous fish, mammals and amphibians convert ammonia to urea in their livers. All fish have kidneys to filter wastes.


Acid Wash? Elasmobranchs have unique urinary systems. Rays and sharks store urea. It moistens their skin. Kidneys process urea into urine. It exits through the skin. Urea makes the meat smell like ammonia, which is a base.


True Gills? External organs, on the heads, behind the eyes of most fish and sharks have gill filaments for breathing capacity. Gills are under the heads of stingrays, rays and some sharks. Gilled mushrooms do not breathe with them.


Operculum? Elasmobranchii lack this hard, plate-like, bony gill covering. It protects the gills of bony fish and helps them pump water over their gills for respiration. Some mollusks and snails also have opercula, or operculums.


Gas Exchange? Few fish have to think to breathe. Gas exchange occurs passively and automatically as they swim. Their gill muscles power oxygen intake. Gases pass into the blood stream. Carbon dioxide seeps out.


Deep Breath? Sharks, stingrays and manta rays breathe unlike most fish. Sharks and manta rays draw water into their mouths and over gill capillaries. Oxygen enters the bloodstream. Water exits but cannot enter gill slits.


Trademark? The large number of slit openings into the gills of Elasmobranchs is unique. Chondrichthyes have five to seven pairs of gill slits opening into one gill. Bony fish have one opening into their many gills.


Oxygen Boost? Some sharks, stingrays and electric rays have supplemental spiracle breathing holes. These external openings bypass mouth-to-gill respiratory flow when obstructions are present and while they are eating.


Perpetual? Active fish breathe with water flowing over gills. Some resting sharks work to pump water by mouth to their gills while inactive. Other sharks and rays oxygenate with spiracles, external respiratory openings.


Quality Control? Were they to breathe through the mouths under their heads, bottom fish would suck sand and grit from the ocean floor. This would be unhealthy. Spiracles aid bottom dwellers, not deep-water mantas or sharks.


Sorbet Style? Spiders and insects have spiracles. On the heads of whales and dolphins, they are called “blow holes”. They also assist the breathing of stationary rays, except mantas. In manta rays the spiracles are nonfunctional.

Movement?

Culture Club? Fish have pectoral fins. Most fish use these fins for steering. Rays use them unlike other fish. Their pectoral fins attach at the head. They swim with wavy motions or flap these fins like bird wings.


Master Stroke? The pectoral fins of angel sharks attach to the body, behind the gills, like those of most fish. Hammerheads swim on their sides. Most sharks, electric rays and bony fish move with caudal fins, or tail fins.


Style Awakening? Dorsal fins keep fish upright. The dorsal fin of a shark is on its back. When breaking the water surface, this triangular fin is widely recognized and respected. It is small or missing in flat rays and flat sharks.


Pair of Aces? Ventral fins are on the underside of fish. They lend balance and stability to swimming and facilitate up or down movements. They are in the pelvic area, in front of the anal fins in those species with them.


Block Chain? Sharks cannot go backwards. It kills them. Most rays move elegantly. Electric rays are slow, awkward exceptions. Lamnid Sharks may be the fastest ocean swimmers, per Pizard's GURPS Miscellanea.

Jaws?

Family Matters? Elasmobranch jaws are detached from the skull. During mating season, some male stingrays develop points on their normally dull, flat teeth. Shark's teeth vary with dietary types. Manta rays have no teeth.


Scheduled Maintenance? Tooth replacement distinguishes Elasmobranchs. Sharks shed and replace tens of thousands of teeth over long lifetimes. Divers and beachcombers often find them. Stingray tooth findings are rare.


Yottabyte? Cookiecutter sharks simultaneously replace rows of teeth. In most sharks, new teeth move forward to fill individual gaps. Stingray teeth also push forward in bands for individual tooth replacement from behind.


Cavity-proof? German researchers found the teeth of some Shark species contain natural fluorinated calcium phosphate. This is a main ingredient in most toothpastes. It makes teeth less prone to decay.


Food Capture? Learn more about Chondrichthyes from contributors to Elsevier B.V. and their trademark ScienceDirect platform. Articles discuss how jaw and tooth structures enable biting, suction or filtering for food.

Extrasensory?

On the Block? Most fish have tongue-like parts, called basihyals. Small basihyals made of cartilage are on the mouth floors of stingrays and sharks. Osteichthyes, or bony fish, have bony basihyals on the floors of their mouths.


Fringe Art? Basihyals serve no purpose in most fish. These largely immobile structures have few muscles and no taste buds. Basihyals add suction to the deep bites of cookiecutter sharks, making them an exception.


Good Taste? All fish can taste. Taste is sensed by the body surface of some fish. Catfish and nurse sharks sense prey with whiskers, called “barbels”. Stingrays and sharks have taste buds lining their mouths and throats.


Extension? Fish nose holes are called nares. They provide the sense of smell. The nares of cartilaginous fish are under their bodies. Fish nares are not connected to their mouths or throats. They play no role in breathing.


Earrings? Elasmobranchs have no otoliths. Bony fish have these ring-like bones of the inner ear. Ring development matches seasonal changes. Like tree-ring dating, scientists examine and count the rings to determine age.


Sharp Note? Internal hearing parts have no outside openings. Ear-like parts or lateral lines sense sound vibrations. Like sonar domes on vessels, echolocation or bio sonar locates and sizes up obstacles or targets.


Doubling Down? Some land and aquatic mammals echo locate. They emit sound waves to sense objects in their environment. Waves bounce back indicating relative locations. Studies show humans can learn echolocation.


Loud and Clear? Some fish identify objects with ultrasound. These species hear at higher frequencies and over greater distances than people. Learn scientific details about What sounds can animals hear? from DOSIT.


Hidden Assets? Some animals use ultrasound to scan and navigate their environment. Ultrasound is used to create images for medical testing. With Sonography, high-frequency sound waves depict organs within bodies.

Seeing is Believing?

View Finder? Manta rays, whale sharks and most sharks have side-facing eyes. Sphyrnid Sharks, or hammerheads, have eyes at each end of hammer-shaped heads. Those of angel sharks and most rays are on top of their heads.


Blind Spots? Whether eyes are front-mounted, top-mounted or side-mounted, most animals have blind spots. Cuttlefish, squid, and octopus rare exceptions. These cephalopod class members are able to see in all directions.


Love Hue? Sight requires light. Acuity varies by species and specimen. Some fish need periods of light and dark. Others live in darkness. Some are blind. Some glow to attract mates or give warning, not as light lanterns.


Glow-Getters? Bioluminescent and biofluorescent sharks glow in the dark. Bioluminescent animals emit light of their own making. Biofluorescent animals absorb light waves to cast green, red, orange or blue glows.


Bioluminescence occurs widely in marine vertebrates and invertebrates. Deep-sea viper dogfish, lantern sharks and cookiecutter sharks are marine examples. Fireflies and fungi are examples of this chemical process on land.


Biofluorescence is not self-powered. These animals absorb sunlight, then emit it as another color with a longer wavelength. Catsharks and swell sharks emit a green light. Visibility presents with low energy, producing no heat.


Amazing Powers: The speed, abilities and traits of fish motivated scientists and engineers to develop submarines, robots and water-proof equipment. Tapping into mind-blowing fish abilities benefits all human beings.