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 Terry Verduin

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 Differences

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 begin life with more cartilage than adults. Bone will replace much of it.


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.


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.


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

Scales?

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.


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


It All Stacks Up? Denticles differ among Elasmobranchs. Fish scales grow with the fish. Denticles stop growing. At a certain size, new ones fill the empty spaces. The pattern is regular in sharks, but irregular in stingrays.


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.

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.


Ancestral Lungs? Like lung air sacs, gills provide an interface between the oxygen and blood. It is unknown if fish gills evolved from ancient lungs, or evolved into lungs used for breathing air. Early fish had both.


Deep Breath? Sharks, stingrays and manta rays breathe unlike the fish majority. These fishy fish draw water by mouth over gill capillaries so oxygen enters the bloodstream. Water exits, but cannot enter the gill slits.


Trademark? The large number of cartilaginous fish gill slit openings is unique. Five to seven pairs of gill slits are on both sides of their heads. Bony fish typically sport just four gills on each side.


Oxygen Boost? Bottom 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.


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. Mollusks and snails also may have opercula, or operculums.


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.


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.

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.


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? Other 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? Ultrasound enables bats and dolphins to scan and navigate their environment. It also is used to create images for medical testing. With Sonography, high-frequency sound waves depict organs within bodies.

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 forth in bands, individually replacing problem spots 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.


Hope for Humans? Doctors at the Department of Animal and Plant Sciences of the University of Sheffield in the UK identified genes for tooth development and lifelong regeneration in sharks. Humans have these genes.


Food Capture? Jaw and tooth structures enable biting, suction or filtering for food. This starts the digestive process of drawing food into the body, absorbing nutrients and extracting wastes for healthy survival.

Digestion?

Screen Test? Animals have different digestive systems with different parts. Most digestive organs are hollow, like mouths, esophaguses, stomachs, intestines and anuses. Livers, gall bladders and pancreases are solid.


Pancreas? Dr. Erika M. Plisetskaya was revolutionary in the Physiology of fish endocrine pancreas. Fish have become the most widely used model for studies of biosynthesis and processing of the pancreatic hormones.


Clean Break? Sharks, skates, rays, guitarfish, sawfish and chimeras have no swim bladders. These gas-filled sacs extend from the digestive system of many bony fishes for buoyancy rather than digestive purposes.


Gall Bladder? Some fish have no gall bladder. The presence may matter to human diners. The Indian Journal of Nephrology gives an example of Acute renal failure following consumption of fish gall bladder.


Esophagus? In fish, the esophagus typically is short. In sharks and rays, the esophageal lining has cilia. These hair-like structures beat in rhythmic waves to facilitate food transport through the digestive tract.


Gill Rakers? These bony or cartilaginous structures present in in filter-feeding fish prevent food particles from exiting between the gill arches. Unlike gill filaments, they are not involved in respiration.


Stomach? Many fish, like goldfish and carp, have no stomach. Digestion, nutrient absorption, fluid and electrolyte balance, within these fish take place in the intestine, which can measure double the body length.


Intestines? Some fish have small and large intestines to regulate digestive hormones, boost metabolism and aid immunity. Sharks are among those fish with single spiral intestine between the stomach and the anal opening.


Anus? In fish, reptiles, egg-laying monotreme mammals and birds, the anal opening also serves as the reproductive opening. This singular, multi-purpose organ is called a “cloaca”.


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.

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.