139 Fun Facts About Shark

What is the skeleton of a shark primarily made of?

Cartilage, the same gristly tissue as in human ears and nose tips, is much lighter than bone, which helps a shark stay buoyant.

How many gill slits do most shark species typically have on each side of their head?

While some species like the sevengill shark have more, the majority of shark species possess five gill slits on each side of their head.

Which shark sense organs detect the electrical fields generated by prey's muscle contractions?

Ampullae of Lorenzini are jelly-filled pores around the snout, sensitive enough to find prey lying hidden under the sand.

Which term describes shark species that lay eggs, often in leathery cases, outside the mother's body?

Oviparous sharks, such as horn sharks, lay eggs that develop and hatch externally, often protected by tough egg cases commonly called 'mermaid's purses'.

What does the whale shark, the largest fish in the sea, mainly eat?

Plankton and krill are strained from the water by the whale shark, which can also hang upright and open its mouth so that food-rich water rushes in.

What is the term for sharks having to swim continuously to force water over their gills?

Ram ventilation is not the only way to breathe: less active sharks such as nurse sharks can lie on the seabed, sucking water in and squeezing it over their gills.

Roughly how many teeth can a shark go through in its lifetime?

Tens of thousands: some sharks get through 30,000 or more, because new teeth keep moving forward from the rows behind to replace any that break or fall out.

Which shark's favourite prey is the stingray, which it finds buried in sand by sweeping the seabed like a metal detector?

Hammerhead sharks spread their electrical sensors across that wide head to scan the sand, and great hammerheads have been seen pinning stingrays down with it before biting.

A shark's skin is often said to feel like what?

Sandpaper is the usual comparison: the skin is covered in tiny tooth-like scales, all pointing towards the tail, that cut drag in the water but feel rough to the touch.

Which organ, enormous in sharks, keeps them buoyant in place of a swim bladder?

The liver, full of light oil, only partly makes up for the missing swim bladder, so sharks also rely on lift from their fins as they swim to hold their depth.

Which sense organ lets sharks feel the vibrations and pressure changes made by prey moving through the water?

Lateral line pores open onto tiny hair cells that register water movement, giving a shark a kind of touch at a distance; the same system helps fish keep together in schools.

What are the small, tooth-like scales covering a shark's skin called?

Dermal denticles all point towards the tail, which cuts drag as water flows over them, and a growing shark sheds them and replaces them with larger ones.

Greenland sharks were shown to live for centuries by radiocarbon dating the centre of which body part?

The eye lens grows in layers through life, so the tissue at its centre dates from the shark's earliest days; a 2016 study put one five-metre shark at around 400 years old.

What term describes sharks such as Great Whites leaping entirely out of the water when hunting seals?

Breaching follows a vertical charge: the great white rushes a seal from deep below so fast that its momentum carries it clear of the surface.

Which small shark was the first shown to be an omnivore, digesting the seagrass that fills much of its gut?

Bonnethead sharks swallow so much seagrass that it can make up 62% of their gut contents, and a 2018 study showed they digest about half of it rather than passing it as waste.

Cookiecutter sharks have left bite craters in which part of submarines?

Sonar domes carry the same round craters these small sharks gouge out of whales and tuna, and the damage has made the species a nuisance to navies.

Which whale shark feature do researchers photograph to identify individual animals, like a fingerprint?

Spot pattern on the skin is unique to each whale shark, and since 2005 researchers have matched photographs of it with a pattern-matching algorithm borrowed from astronomy.

What is the main job of the spiracle, an opening behind each eye in many bottom-dwelling sharks?

Water intake for respiration: a shark resting on the seabed draws water in through the spiracle to its gills, so it can breathe without swimming and while its mouth is busy eating.

What term describes sharks whose eggs hatch inside the mother before live birth?

Ovoviviparous sharks hatch inside the mother, and in makos and porbeagles the unborn pups then feed on unfertilised eggs she keeps producing; many biologists now call this aplacental viviparity.

What is the common name for the smallest known shark species?

The dwarf lanternshark, known only from deep water off Colombia and Venezuela, reaches about 20 cm at most and, like other lanternsharks, produces its own light.

Which aquarium was the first to keep a great white on display long-term, for nearly 200 days in 2004-05?

Monterey Bay Aquarium had lost its first great white after 11 days in 1984 because it would not eat, and before the 2004 shark none had survived more than 16 days in any tank.

What material makes up the outer, hardest layer of a shark's tooth?

Enameloid in shark teeth is built from fluorapatite, a fluoride mineral, yet a 2012 study found that shark teeth are no harder than human ones.

What trance-like state do some sharks enter when they are turned upside down?

Tonic immobility sets in within about a minute and can last around 15 minutes, so researchers turn sharks over on purpose to handle them safely.

What did a 2021 study blame for a 71% fall in oceanic shark and ray numbers since 1970?

Overfishing: fishing pressure on these ocean-going species rose 18-fold over the period, leaving three-quarters of them threatened with extinction.

Which swimwear brand modelled the ridged fabric of its Fastskin racing suits on shark skin?

Speedo said the ridges channelled water as a shark's skin does, but a 2012 Harvard study found the suit's surface did nothing to cut drag: 'it's nothing like shark skin at all'.

Which low-density oil fills the organ sharks rely on to stay buoyant?

Squalene takes its name from Squalus, a genus of sharks, and demand for it in cosmetics and vaccines is one reason deep-sea sharks are still fished.

Which shark species has a whip-like tail, as long as its body, used to stun prey?

Thresher sharks were long only suspected of hunting with the tail, until film shot off the Philippines in 2010 showed single slaps stunning several sardines at once.

Which pink-skinned deep-sea shark shoots its jaws forward to snatch prey from beneath a long, flat snout?

The goblin shark flings its jaws out at up to 3.1 metres a second, the fastest jaw thrust measured in any shark, which makes up for its being a weak swimmer.

A 2020 study found that whale sharks protect which body part with a covering of tiny tooth-like scales?

Their eyeballs are armoured with scales shaped differently from those on the body, and a whale shark can also pull each eye deep back into its socket for protection.

What nourishes hammerhead pups in the womb?

A placenta forms when the embryo's used-up yolk sac attaches to the wall of the womb, and blood vessels running through it then feed the pup until birth.

Which deep-water filter-feeding shark was unknown to science until 1976?

The megamouth shark was unknown until 1976, when one became tangled in the sea anchor of a US Navy research ship in the Pacific; it is the smallest of the three filter-feeding sharks.

Which slender open-ocean shark is caught by the million each year, often as bycatch on longlines?

Blue sharks were long an accidental catch for fleets after other fish, yet anglers seek them out on purpose as a game fish.

What adaptation lets the cookiecutter shark cut neat, circular plugs of flesh from its prey?

Suction lips clamp the shark on while its saw-like lower teeth carve out a plug as it twists, leaving round scars on tuna, dolphins and whales.

A dead shark gradually starts to smell strongly of what, as bacteria break down its urea?

Ammonia forms as bacteria break down urea, which sharks hold in their blood and tissues to keep their body fluids in balance with salty seawater.

Male sharks fertilize internally using which paired organs?

Claspers are modified pelvic fins, analogous to a mammalian penis; the male inserts only one of the pair at a time to transfer sperm.

Some sharks swallow air at the surface and hold it in the stomach in order to do what?

Hover in mid-water: sharks are denser than water and have no swim bladder, so one species uses a stomach full of swallowed air as a float to hang motionless.

Which sense lets a shark follow a faint trail of blood through the water to wounded prey?

Smell also tells a shark which way to turn: experiments in 2010 showed it steers towards whichever nostril picks up the scent first.

Which ocean habitat are sharks almost entirely absent from?

The abyssal depths below about 3,000 metres hold bony fish but almost no sharks, probably because too little food sinks that far to fuel them, a 2006 survey proposed.

Which carpet shark hatches with bold stripes that give way to spots as it grows?

Zebra Shark pups and spotted adults look so unlike each other that they were once taken for separate species; the tail fin makes up nearly half its length.

What is the term for the 'virgin births' recorded in captive female sharks kept apart from males?

Parthenogenesis was first proved in a shark in 2007 by DNA tests on a pup born in an aquarium; the young are not clones, carrying only a reshuffled half of the mother's genes.

Which fish hitches rides on sharks using a suction disc on top of its head?

The remora's first dorsal fin is modified into a ridged suction disc that clamps onto sharks, rays and turtles, letting it travel for free and feed on scraps and parasites.

Which large, slow-moving shark keeps its massive mouth open to filter feed while swimming?

Basking Shark is the second-largest fish and takes its name from its habit of feeding slowly at the surface, where it looks as if it is basking in the sun.

Sharks have a heterocercal tail fin, meaning which part is usually noticeably larger?

In a heterocercal tail the upper lobe is larger, with the vertebral column extending into it; most bony fish have symmetrical, homocercal tails instead.

Great whites sometimes hang upright with the head poking out of the water, a behaviour shared with whales and called what?

Spy-hopping is better known from whales and dolphins; a great white doing it is thought to be getting a look at whatever is happening above the surface.

Which Pacific island nation, home to the famous Jellyfish Lake, declared the world's first shark sanctuary in 2009?

Palau's president announced the ban on commercial shark fishing at the UN General Assembly, and the Maldives, Honduras and the Bahamas later created sanctuaries of their own.

The eyes of most sharks are adapted to see best in what?

Low light conditions suit sharks because a mirror-like layer behind the retina, the tapetum lucidum, bounces light back for a second pass, as it does in a cat's eye.

Which eel-like deep-sea shark has an exceptionally long pregnancy, estimated at one to three and a half years?

The frilled shark's embryos feed only on yolk and grow so slowly that estimates of its pregnancy run from a year or two up to three and a half; pups are born 40 to 60 cm long.

Which small shark is known for 'walking' along the seabed on its paddle-like fins?

The epaulette shark walks between tide pools when the falling tide strands it on the reef, and can survive for hours in water with almost no oxygen left.

Unlike bony fish, how are a shark's gill slits arranged?

Uncovered, in a row behind the head: a bony fish instead hides its gills under one hard cover, the operculum, which it also uses to pump water across them.

Which German word for 'scoundrel' is one suggested source of 'shark' in the sense of a swindler?

Schurke, through the dialect form Schork, may lie behind the swindler; the fish name's origin is uncertain, and one theory holds that the cheat came first and the fish was named after him.

The largest megalodon teeth were roughly as long as which of these?

An adult's hand is about as long as the biggest megalodon teeth, which reach 18 cm; no complete skeleton has ever been found, so the shark's size has to be worked out from teeth like these.

Which heat-exchange structure lets makos and great whites keep muscles warmer than the sea?

Rete mirabile is a mesh of vessels in which warm blood leaving the muscles passes its heat to cold blood arriving from the gills, so the warmth stays in the body instead of leaking into the sea.

A tagged great white stunned scientists by crossing the Indian Ocean from Africa to which country and back in under nine months?

Australia and back, about 20,000 km, was the fastest return ocean crossing then known for any swimming animal, and it linked two far-apart great white populations.

Sharks' teeth are embedded in what, rather than fixed to the jaw?

Shark teeth sit in the gums rather than in sockets in the jaw, so rows of replacement teeth move forward like a conveyor belt throughout life.

Which animal sometimes preys on the great white, normally an apex predator?

Orca visits to California's Farallon Islands, however brief, have driven the great whites there away for long periods, sparing the local elephant seals.

Which country has legally protected the great white since 1991?

South Africa made the great white a protected species in 1991, yet the shark nets off KwaZulu-Natal's bathing beaches went on catching and killing them.

The 'White Shark Cafe', where great whites gather mid-ocean, lies between Baja California and where?

Hawaii and Baja California bracket a patch of ocean long written off as a desert, until a 2018 expedition found deep layers of squid and fish that may explain the sharks' visits.

The largest reliably measured whale shark was about as long as what?

A bowling lane runs 18.3 metres from foul line to head pin, and the record whale shark measured 18.8; bigger ones have been reported, but such giants are hard to measure and inflated sizes are common in print.

The first whale shark known to science was harpooned in 1828 in Table Bay, the harbour of which city?

Cape Town housed British troops at the time, and it was an army doctor serving with them, Andrew Smith, who described the harpooned fish as a new species.

The whale shark strains its food through which structures?

Filter pads, twenty sieve-like plates, hold back the food while the water passes out through the gills; the 300 or so rows of tiny teeth are thought to play no part in feeding.

Which Western Australian site hosts a famous seasonal whale shark aggregation?

Ningaloo Reef draws whale sharks from March each year; a decade of measuring them there showed males level off at eight to nine metres while females keep growing, so the biggest whale sharks are female.

Which shark is second only to the great white in recorded fatal attacks on humans?

The tiger shark trails only the great white in recorded fatal attacks because it hunts in shallow reefs, harbours and river mouths where people swim, and bites almost anything, even licence plates and old tyres.

Which British artist's 1991 work is a real shark suspended in a tank of formaldehyde?

Damien Hirst called it The Physical Impossibility of Death in the Mind of Someone Living; the badly preserved original decayed in its tank and was later replaced with a new shark.

Which protective eyelid do tiger and blue sharks have that great whites lack?

Nictitating membrane is the name for this tough inner eyelid, which tiger, blue and other requiem sharks draw across the eye as they bite; great whites have none and roll their eyes backwards instead.

Which hammerhead has proportionally the widest head, spanning up to half its body length?

Winghead sharks carry a narrow, wing-like 'hammer' 40 to 50 per cent as wide as the body is long, and its far-apart eyes are thought to give them superb binocular vision.

What is the name of the fictional New England island resort terrorised by the shark in Jaws?

Amity Island lives on its summer visitors, so its mayor keeps the beaches open for the Fourth of July weekend despite the first attacks, and the shark strikes again in front of the holiday crowds.

Which change is thought to have helped drive megalodon extinct about 3.6 million years ago?

Cooling seas at the onset of the ice ages are thought to have shrunk megalodon's warm-water range and coastal nurseries, while the whales it hunted dwindled or shifted toward the poles.

Megalodon's jaws could exert a bite force of up to roughly how many newtons?

A 2008 study estimated megalodon's bite at 108,500 to 182,200 newtons, among the strongest of any animal; its thick teeth were built for grabbing prey and breaking bone.

After whom did the Jaws crew nickname the mechanical sharks 'Bruce'?

Spielberg's lawyer, Bruce Ramer, gave his name to the three mechanical sharks, which failed so often at sea that Spielberg kept the shark unseen for much of the film.

Jaws was shot mostly on location on which Massachusetts island?

Martha's Vineyard doubled as the film's resort town; Spielberg insisted on shooting on the open ocean there instead of in a studio tank, which sent the production far over schedule and budget.

What was the original budget and shooting schedule for Jaws?

Jaws was budgeted at $3.5 million with a 55-day shoot; it ended up taking 159 days and about $9 million, partly because the mechanical sharks kept breaking down.

Jaws overtook which film as the highest-grossing at the North American box office in just 78 days?

The Godfather lost its record to a new kind of release: Jaws opened in more than 400 cinemas at once behind heavy television advertising, the template for summer blockbusters ever since.

Which subplot of Peter Benchley's novel did Steven Spielberg cut when filming Jaws?

Ellen Brody's affair with Hooper was dropped, along with the mayor's Mafia ties, because Spielberg found the novel's characters so unsympathetic that he had wanted the shark to win.

Which Jaws character says 'You're gonna need a bigger boat' after his first close look at the shark?

Chief Brody says it to Quint, stunned, moments after the shark rears up behind him; Roy Scheider improvised the line, which the American Film Institute ranks 35th among its top 100 movie quotes.

Roughly how many unprovoked shark attacks are reported worldwide each year?

Only the great white, tiger and bull are responsible for double-digit fatal totals.

Which cable channel has aired Shark Week every summer since 1988?

Discovery Channel began the week in July 1988 to correct misconceptions about sharks, yet in 2013 its line-up included a fictional film, presented as a documentary, suggesting megalodon was still alive.

Shark fin soup, the dish that drives the fin trade, is a banquet tradition of which cuisine?

Chinese hosts serve the soup at weddings and banquets as a mark of status; the fin adds texture but almost no flavour, and demand for it leads fishers to slice off fins and dump the sharks at sea.

How do scientists usually estimate the age of a shark?

Counting rings in its vertebrae works like counting tree rings: the backbone lays down paired light and dark bands as the shark grows, and each pair is usually read as one year.

Eating untreated Greenland shark meat causes symptoms most often compared to what?

Extreme drunkenness is the classic description: the flesh is loaded with trimethylamine oxide, and those who eat it fresh stumble and vomit, so Icelanders ferment and dry it for months to make hakarl.

Which American marine biologist's pioneering shark research earned her the nickname 'Shark Lady'?

Eugenie Clark founded the laboratory that became Mote Marine Laboratory, and her dives among Mexico's sleeping sharks upended the belief that sharks must keep swimming to breathe.

Which shark has been found far up the Mississippi and in Lake Nicaragua?

Bull sharks cope so well with fresh water that Lake Nicaragua's sharks were once thought a landlocked species of their own, until they proved to be bull sharks that reach the sea by river.

Before science knew them as shark teeth, fossil megalodon teeth went by what name?

Tongue stones were said in Roman times to have fallen from the sky; in 1666 Nicolas Steno dissected the head of a huge shark caught off Livorno and argued that the stones were teeth from long-dead sharks.

The nurse shark's genus name Ginglymostoma means what in Greek?

Hinged mouth is what Ginglymostoma means, from Greek ginglymos, 'hinge', and stoma, 'mouth'; the nurse shark works that small mouth like a vacuum, sucking fish out of crevices and conchs out of their shells.

Female lemon sharks born at Bimini return there years later to do what?

Bear their young: two decades of DNA profiling at Bimini in the Bahamas showed that females come back to the very nursery where they were born when it is their turn to give birth.

Which sharks of Australian reefs hide behind a fringe of skin flaps?

Wobbegongs lie still on the seabed, their carpet-patterned skin and fringe of lobes blending into rock and weed, then snap up fish that stray too close.

Which flat-bodied sharks are often mistaken for rays as they lie buried in the sand?

Angel sharks have flattened bodies and broad, wing-like fins but are true sharks; they bury themselves in sand and burst upward to seize fish that pass overhead.

Unlike sawfish, sawsharks carry a pair of what halfway along the snout?

Long barbels hang from the middle of a sawshark's snout and its gill slits sit on the sides of the head, which tells it apart from a sawfish; the sawshark is thought to swipe its toothed snout sideways to cripple prey.

The name of the mako shark comes from which language?

Maori gave English the word: there mako names the shark and also its tooth, which Maori wore as a prized ear pendant.

A shark's dark back and pale belly, hiding it from above and below, is an example of which camouflage?

Countershading works both ways: seen from above, the dark back merges with deep water, and seen from underneath, the pale belly merges with the bright surface; the great white is named for that white underside.

Which shark is notorious for attacking survivors of shipwrecks and plane crashes?

Oceanic whitetip sharks live far from land, so they are the sharks that find people adrift; when a U-boat sank the steamship Nova Scotia in 1942, many of the deaths were blamed on them.

Which steamship carrying about 1,000 people was sunk by a U-boat in November 1942, drawing oceanic whitetips?

The RMS Nova Scotia, carrying about 1,000 people including Italian internees, was torpedoed by U-177 off South Africa on 28 November 1942; fewer than 200 survived, and oceanic whitetips were blamed for many deaths.

The Port Jackson shark lays a tough egg case of what distinctive shape?

Corkscrew: the twisting ridges let the newly laid case be wedged into a rock crevice, where it stays for most of a year until the pup hatches.

In the 1916 shark attacks, two victims were killed the same day in what unlikely setting?

A creek: the shark swam up Matawan Creek, miles from the open sea, pulled 11-year-old Lester Stillwell under and fatally bit Stanley Fisher, who had dived in to find the boy.

USS Indianapolis was sunk in 1945 after delivering what?

Atomic bomb parts and nuclear material reached Tinian on 26 July; four days later a Japanese submarine sank the cruiser, and sharks preyed on the hundreds of men left adrift for days.

How did the US Navy finally learn that USS Indianapolis had been sunk?

A patrol plane spotted survivors by chance on 2 August 1945, more than three days after the sinking; nobody ashore had reported the cruiser overdue, and only 316 of her crew were saved.

Which Australian surfer fought off a shark on live television during the 2015 J-Bay Open final?

Mick Fanning punched the shark after it tangled in his leg rope at Jeffreys Bay, and it bit the rope through and left; he returned a year later and won the same event.

Shark nets were first strung off the beaches of which city, in 1937?

Sydney's beaches were first meshed in 1937 after years of attacks; the nets do not seal a beach off, and work instead by catching large sharks that pass nearby.

Rodney Fox was attacked by a great white in 1963 while competing in what?

A spearfishing championship in South Australia, where Fox was defending his title; he needed 462 stitches, then went on to build the first cage for watching great whites underwater.

Which actor missed collecting his first Oscar in 1987 because he was filming Jaws: The Revenge?

Michael Caine was on set in the Bahamas when he won for Hannah and Her Sisters; he later said he had never seen the shark film, but had seen the house it built, 'and it is terrific'.

Jaws author Peter Benchley wrote White House speeches in the late 1960s for which president?

Lyndon B. Johnson employed Benchley from 1967 until he left office; Benchley then scraped by on freelance writing until a publisher backed his idea for a novel about a man-eating shark.

Which actor, famous for his gangster roles, voices the shark mob boss Don Lino in Shark Tale?

Robert De Niro's Don Lino sends his henchmen after the killer of his son Frankie, not knowing that the fish hailed as the 'Sharkslayer', Will Smith's Oscar, merely took the credit.

The cult TV movie Sharknado first aired on which channel on July 11, 2013?

Syfy's film starred Tara Reid and Ian Ziering, whose Fin jumps into a shark's mouth with a chainsaw and cuts his way out.

Which South Korean company's version of 'Baby Shark' went viral after its June 2016 release?

Pinkfong did not write the song: the tune is older and believed to be in the public domain, but the company's 2016 dance video became the first on YouTube to reach ten billion views.

Which song did 'Baby Shark Dance' overtake in 2020 to become YouTube's most-viewed video?

Despacito lost its crown to a toddlers' sing-along that had taken off in 2017, when a dance challenge that began in Indonesia carried it around the world.

Which actor played the grizzled shark hunter Quint in Jaws?

Robert Shaw got the part after Lee Marvin turned it down and Sterling Hayden's tax troubles ruled him out; a playwright himself, he reworked Quint's best-known speech.

The prehistoric 'buzzsaw shark' Helicoprion is famous for what dental structure?

A tooth whorl, a coil of teeth like a circular saw, sat in its lower jaw, though where it belonged was long debated; Helicoprion was no true shark but a relative of today's chimaeras.

What do fishers and dive boats call the fish scraps and blood tipped overboard to draw sharks in?

Chum, known as berley to Australians, drifts away on the current and sharks follow it back to the boat; cage-diving operators use it to bring great whites within view of their divers.

Which shark's most developed embryo eats its siblings in the womb, called adelphophagy?

The sand tiger's largest embryo in each womb eats the eggs and smaller embryos around it, so every pregnancy ends with just two large pups, one from each uterus.

Which harmless houndshark is common in bays along the US Pacific coast?

The leopard shark, named for its dark saddles and spots, travels in large schools that follow the rising tide onto mudflats, where they dig out clams, worms and crabs.

The blue shark is the only living species of which genus?

The blue shark, Prionace glauca, is the sole living member of its genus; a slender open-ocean requiem shark, it prefers cooler water and commonly reaches 2 to 3 metres.

The bonnethead is the only shark known to show sexual dimorphism in what?

Head shape sets the sexes apart: females keep a smoothly rounded front edge, while males grow a distinct bulge along it as they mature; bonnetheads usually swim in small schools of up to 15.

Silky sharks are often caught as bycatch because they trail schools of which fish?

Tuna crews in the eastern Pacific call silky sharks net-eaters for the damage they do to nets and catches; the name silky comes from the shark's smooth skin.

In which Hemingway novella do sharks strip a Cuban fisherman's giant marlin to the bone?

The Old Man and the Sea ends with Santiago, who has killed several of the sharks, towing home nothing but a skeleton; the book won a Pulitzer and was singled out when Hemingway received the Nobel Prize.

Where do whitetip reef sharks spend much of the day?

Resting inside caves is possible because, unlike most of its relatives, the whitetip reef shark can lie still and pump water over its gills; at night it squirms into crevices after hidden prey.

In which 2016 thriller is Blake Lively's surfer stranded on a rock 200 yards from shore by a great white?

The Shallows strands its heroine, a medical student mourning her mother, on a rock in a Mexican bay, where she must outwit the shark circling between her and the beach.

Which action star plays the rescue diver who takes on a giant prehistoric shark in The Meg?

Jason Statham, a competitive diver before he acted, plays Jonas Taylor, sent down to save a crew trapped on the sea floor; the 2018 film is loosely based on Steve Alten's novel Meg.

In Deep Blue Sea (1999), scientists enlarge the brains of mako sharks while seeking a cure for what?

Alzheimer's disease is the target: the scientists enlarge the makos' brains to harvest more of a protein, and the sharks, made cleverer by the change, turn on the crew of the undersea laboratory.

Open Water (2003) was inspired by a couple abandoned by their dive boat on which reef?

Great Barrier Reef crew did not miss Tom and Eileen Lonergan until a bag of their belongings turned up on the boat two days later, so the search began only then and the couple were never found.

In Finding Nemo, the great white shark Bruce leads a support group of sharks trying to do what?

Stop eating fish is the pledge of Bruce's support group, but his resolve lasts only until Dory is accidentally hurt: one trace of her blood and he relapses into a full-scale rampage.

Which future TV chef helped develop a shark repellent for the OSS spy agency during World War II?

Julia Child cooked up test concoctions to stop curious sharks setting off underwater explosives. The work has been called her first foray into the world of cooking.

Fossil scales suggest sharks or their ancestors swam the seas 450 million years ago, before which of these existed?

Trees came later: the earliest evolved around 400 million years ago, by which time the forerunners of sharks had been swimming for some 50 million years.

What nickname do beachcombers give the leathery egg cases of sharks and skates that wash up on shore?

Mermaid's purse cases are built from strands of collagen and usually hold just one embryo, though a big skate's capsule can carry up to seven.

The phrase 'jump the shark', for a show past its best, comes from a water-ski stunt on which 1970s sitcom?

Happy Days sent Fonzie over a confined shark on water-skis in 1977, still wearing his leather jacket. Two college roommates coined the phrase eight years later.

'Left Shark' became an internet sensation after dancing out of step behind which singer at Super Bowl XLIX?

Katy Perry was flanked by two dancers in shark costumes during 'Teenage Dream', and the one on the left went its own way. It was later revealed to be Bryan Gaw.

The name megalodon, given to a giant prehistoric shark, comes from Ancient Greek words that together mean what?

Big tooth fits: megalodon is known only from fragmentary remains, chiefly fossil teeth and vertebrae, so its true size and appearance are still uncertain.

Hákarl, shark meat that is fermented and then hung to dry for months, is a national dish of which country?

Iceland serves hákarl at its midwinter festival, þorrablót. Chef Anthony Bourdain called it the single worst thing he had ever eaten.

Which composer won an Oscar for the score of Jaws, built around a menacing two-note shark theme?

John Williams first played the two notes on a piano for the film's director, who is said to have laughed, thinking it was a joke.

Which teenage surfer was back on her board within a month of losing her left arm to a shark off Kauai?

Bethany Hamilton was 13 when she was bitten in 2003, and she surfed again just 26 days later. Her memoir Soul Surfer became a 2011 feature film.

In the 1970s, cookiecutter shark bites to rubber sonar domes forced which vessels back to base for repairs?

US Navy submarines began leaking sound-transmitting oil, and an unknown enemy weapon was feared at first. Fibreglass covers around the domes solved the problem.

Which fin stands upright on a shark's back and is famously seen slicing through the surface of the water?

The dorsal fin works as a stabiliser, keeping a shark from rolling over and helping it make sudden turns. Sharks typically have two along the midline.

Which US state contains Volusia County, which shark researchers have dubbed the 'shark bite capital of the world'?

Florida's Volusia County includes New Smyrna Beach, where a newspaper photographer once caught a spinner shark leaping clean over a surfer.

A 1992 book popularised the false claim that sharks never get which disease, fuelling sales of shark supplement pills?

Cancer does strike sharks: tumours have been found in a number of species, the first of them recorded in 1908. Controlled trials found no benefit from the pills.

What is the practice called when boat crews throw chunks of bait and blood into the sea to lure sharks?

Chumming draws sharks in so reliably that Alabama outlawed it within 300 feet of the shoreline, to keep them away from swimmers.

The kitefin shark of the deep sea is the largest vertebrate on record with which unusual ability?

Glowing in the dark, the kitefin sends its light downwards from its belly, perhaps to illuminate the sea floor as it hunts or to hide its outline from prey.

On the TV game show Card Sharks, contestants must predict whether the next oversized playing card will be what?

Higher or lower was the call on every card, but contestants first had to win control of the board by judging how 100 people had answered a survey.

The Roman writer Pliny the Elder recorded a belief that fossil shark teeth fell from the sky during which events?

Lunar eclipses brought them down, in a tale Pliny repeated with open doubt, the oldest known record of the fossils. In the 1660s Nicolas Steno matched the stones to the teeth of a huge shark caught near Livorno.

Which mirror-like tissue behind the retina helps sharks see in dim water by reflecting light back through the eye?

Tapetum lucidum tissue gives light a second pass through the retina. In cats it shines so brilliantly that ancient Egyptians believed it reflected the sun at night.

The blacktip shark and the oddly named nervous shark both belong to which family of live-bearing warm-sea sharks?

Requiem sharks may owe their name to requin, the French word for shark. Every species in the family gives birth to fully developed young.

Sharks make up for a very short intestine with which internal structure that increases its absorbing surface?

Spiral valve is the name for the corkscrew-shaped lower intestine, which holds food back so that it is almost fully digested. Many sharks therefore feed only infrequently.