97 Fun Facts About Sea Life

Which marine mammal, like humans, is one of the few animals whose females live decades after they stop breeding?

Orcas are among the few animals that undergo menopause; older females lead the pod to salmon, most of all in years when the fish are scarce, which may be why they live on for decades.

'Ming', caught off Iceland in 2006 and aged at 507 years, was the oldest known individual of what kind of animal?

A clam of the ocean quahog species, Ming was named by Sunday Times journalists after the Chinese dynasty in power when it was born around 1499.

What decides whether a sea turtle hatchling is male or female, rather than its chromosomes?

Nest temperature sets the sex: warmer sand produces female hatchlings and cooler sand males, a system called temperature-dependent sex determination.

Which deep-water fish from off Australia was voted the world's ugliest animal in a 2013 online poll?

The blobfish won the Ugly Animal Preservation Society's vote and became its mascot; at 600–1,200 m its gelatinous flesh holds its shape and looks far less droopy.

Which shore snail's teeth outperform spider silk as the strongest known biological material?

Limpet teeth are packed with fine fibres of goethite, an iron mineral, which makes them stronger than spider silk, the record holder among natural materials until they were tested.

Seahorses must eat almost constantly because their very simple gut lacks which organ?

A stomach is missing, so food rushes straight through: a seahorse spends its day anchored by its tail, sucking in tiny crustaceans as they drift within reach.

Which fish was filmed in 2022 at 8,336 m in the Izu–Ogasawara Trench, deeper than any fish had been seen before?

A snailfish of the genus Pseudoliparis, filmed by a baited camera lander, beat the 8,178 m record set in the Mariana Trench; the expedition's leader thinks no fish can survive much deeper.

The green sea turtle takes its name from the colour of which part of its body, not its shell?

Its fat gives the green turtle its name, a colour long put down to its diet of seagrass and algae, although other sea turtles have greenish fat too; the shell itself is olive to black.

Inky the octopus made world news in 2016 by slipping out of Napier's National Aquarium through what?

A drain pipe running out to sea was Inky's exit: the common New Zealand octopus left his tank, crawled across the floor and vanished down it.

Two-metre geometric circles in the sand off Japan's Ryukyu Islands turned out to be the nests of which fish?

A pufferfish, Torquigener albomaculosus, sculpts the ridged 2 m circles: males build them to attract females, and the species was described from specimens off Amami Ōshima.

What do sea otters wrap around themselves before resting so they do not drift out to sea?

Kelp fronds act as an anchor for a resting otter, and a foraging mother leaves her pup wrapped in kelp on the surface while she dives; it cries loudly until she returns.

Moray eels are the only animals known to seize prey with a second set of what, shot forward from the throat?

Pharyngeal jaws sit far back in the head and look like the mouth's own jaws, complete with tiny teeth; the eel launches them to haul prey down its gullet.

Which jellyfish sees with 24 eyes, some complete with a lens, cornea and retina?

The box jellyfish carries six eyes on each of four sensory clubs called rhopalia, and uses its lens eyes to steer around obstacles in its path.

'Aristotle's lantern', named from his History of Animals, is the chewing organ of which creature?

The sea urchin's chewing apparatus takes the name from a passage in Aristotle's History of Animals, though a 2008 study argued he was likening the animal's whole shell, not its mouthparts, to a lantern.

A sawfish's toothed 'saw' is an extension of which part of the ray's body?

Its snout, or rostrum, is lined with teeth and packed with electroreceptors, so the saw both detects prey and slashes at it; despite their shark-like build, sawfish are rays.

Nesting sea turtles seem to weep on the beach; what are the tears actually getting rid of?

Excess salt leaves through a lachrymal gland in each eye socket, making the tears saltier than seawater; reptile kidneys cannot produce urine that concentrated.

When startled, some sea cucumbers defend themselves by expelling what through their rear end?

Their own guts: sea cucumbers can eviscerate, expelling the intestine and other organs through the rear end and regrowing them; some reef species instead fire sticky Cuvierian tubules out of the cloaca to tangle an attacker.

Which city's Toyosu fish market sold a single bluefin tuna for 333.6 million yen at its first auction of 2019?

Tokyo's first auction of the year draws showpiece bids: sushi-chain owner Kiyoshi Kimura paid about US$3.1 million for the fish on 5 January 2019, around double the previous record.

Migrating sea turtles cross open ocean and find their way home by sensing what?

Earth's magnetic field gives sea turtles both a map and a compass sense, called magnetoreception, which lets them hold course inside strong ocean gyres.

Which cetacean has been filmed dozing in groups, hanging motionless and upright with its head near the surface?

The sperm whale rests in short bouts this way; a 2008 study that tagged the whales found the naps add up to only about 7% of their time.

Which deep-sea crustacean, a relative of the garden woodlouse, can reach 50 cm long?

The giant isopod Bathynomus giganteus usually runs 19–36 cm, and the largest confirmed specimen measured about 50 cm; a 76-cm claim came only from the popular press.

The heaviest bony fish ever recorded, a 2,744-kg giant found off the Azores, was what kind of fish?

A sunfish of the species Mola alexandrini, it was found floating dead off Faial island in December 2021 and had to be hauled back to port before anyone could weigh it.

Which sea turtle is the deepest diver, recorded going down about 1,200 m?

Leatherback turtles, named for the rubbery skin they have in place of a bony shell, have been recorded diving more than 1,200 m, deeper than most marine mammals go.

Which crustacean's eyes carry at least 12 types of photoreceptor, against four in humans?

The mantis shrimp sees from deep ultraviolet to far-red and detects polarised light, yet a 2014 study found it surprisingly poor at telling similar colours apart.

The naval torpedo took its name from a genus of which fish?

Electric rays of the genus Torpedo stun with a shock; the Latin torpedo already meant both 'numbness' and the fish itself, and the weapon simply borrowed the name.

The chalky 'cuttlebone' sold for caged birds to peck is which part of a cuttlefish?

Its internal shell is a brittle, gas-filled buoyancy organ found in every member of the family Sepiidae, and pet shops sell it as a calcium supplement for birds, reptiles and snails.

A deep-sea octopus in Monterey Canyon guarded one clutch of eggs for how long, a record for any animal?

53 months is the longest egg-brooding known in any animal; the Graneledone boreopacifica mother was monitored by the Monterey Bay Aquarium Research Institute, and that vigil alone outlasts most octopuses' entire lives.

A 10.6-metre female found carrying about 300 embryos proved that which shark bears live young?

The whale shark's breeding was long debated: an egg found in the Gulf of Mexico in the 1950s suggested it laid them, until this female showed the eggs hatch inside the mother.

Millions of glowing firefly squid gather each spring to spawn in which Japanese bay, lighting its shores blue?

Toyama Bay fills with firefly squid on their yearly breeding migration; they flash blue light from photophores, and the glowing run draws tourists as well as fishing boats.

A group of jellyfish drifting together is known by which collective name?

A smack is the collective noun, and a big one can do damage: in 2011 a mass of jellyfish clogged the seawater filters at Scotland's Torness nuclear plant, and both reactors were shut down.

The four horseshoe shapes visible through a moon jellyfish's bell are which organs?

Its gonads show as four pale horseshoes because Aurelia aurita is almost entirely translucent; the bell is usually 25–40 cm across.

Stings from Carukia barnesi, a tiny Australian jellyfish, cause which illness?

Irukandji syndrome was named in 1952 by Hugo Flecker after the Aboriginal people of the Palm Cove area near Cairns; the sting barely registers, then headache, vomiting and severe anxiety follow.

The leafy seadragon, a seahorse cousin draped in weed-like lobes, is the marine emblem of which Australian state?

South Australia made the 'leafy' its marine emblem in 2001, having fully protected it since 1987 after pollution and aquarium collectors thinned its numbers; Victoria's emblem is the weedy seadragon.

Which rorqual, nicknamed 'the greyhound of the sea' for its speed, has a white right lower jaw and a dark left one?

The fin whale's asymmetry runs across its whole head, dark grey on the left but patterned on the right, and speeds of 46–50 km/h earned it the nickname.

Giant tube worms at Pacific hydrothermal vents grow to 3 m while completely lacking what?

A digestive system is absent in adult Riftia pachyptila; sulfur-oxidising bacteria inside the worm turn vent hydrogen sulfide into food, and it grows faster than any known marine invertebrate.

Which small fish, up to 65% of all deep-sea fish biomass, once fooled wartime sonar as a 'false sea floor'?

Lanternfish gas bladders reflect sonar so strongly that Second World War operators saw a phantom seabed 300–500 m down by day, shallower at night as the shoals rose to feed.

The 'Bloop', a huge low-frequency sound picked up by NOAA hydrophones in 1997, was eventually traced to what?

Cracking ice was the culprit: by 2012 NOAA matched the Bloop to non-tectonic cryoseisms, the noise of glaciers calving or ice gouging the seabed, rather than any animal.

The painkiller ziconotide, infused into the spinal fluid for severe chronic pain, was derived from the venom of what?

A cone snail, Conus magus, makes the omega-conotoxin that ziconotide copies synthetically; taken by mouth or vein it is ineffective or too toxic, so it must be pumped straight into the spinal fluid.

A specimen washed up at St Andrews in 1864 topped 55 m; which creature is Guinness's longest solitary animal?

The bootlace worm, a ribbon worm of North Sea shallows, was measured at over 55 m after a severe storm; typical specimens run 5–15 m, and the record may reflect a body stretched beyond its usual length.

Which small Indo-Pacific cuttlefish ambles across the seabed on its arms rather than darting away from danger?

The flamboyant cuttlefish walks on its lower arms and flashes vivid warning colours instead of fleeing; one study reported its flesh highly toxic, though the toxin has yet to be isolated.

What actually produces the loud crack a pistol shrimp makes when it snaps?

A bubble collapsing off its claw makes the snap: the claw shuts so fast that it fires a jet of water, leaving a cavitation bubble whose collapse cracks loudly enough to stun small fish.

Which shark, the smallest known at about 20 cm, lives on the upper continental slope off Colombia and Venezuela?

The dwarf lanternshark, Etmopterus perryi, is known only from deep water in that corner of the Caribbean; lanternsharks light up their bellies, most likely to hide their outline from hunters below.

The stoplight loosejaw hunts the deep with a beam of which colour, one almost no other deep-sea animal can see?

Red bioluminescence is produced by only a few fish genera, and Malacosteus is unique among animals in using a chlorophyll derivative to see its own red beam.

Comb jellies, which row through the water with bands of beating hairs, belong to which phylum of animals?

Ctenophora takes its name from the Greek for 'comb' and 'carry'; comb jellies are not true jellyfish, and fossils put the phylum in the early Cambrian, more than 500 million years ago.

Bargibant's pygmy seahorse was only found in 1969 when its host was collected for a Nouméa museum; what was that host?

A gorgonian sea fan of the genus Muricella hid the 2-cm seahorse so well that Georges Bargibant spotted it only while examining the coral in the laboratory.

Which sea turtle nests only on Australian shores and, unlike its relatives, skips the long open-ocean phase of life?

Flatback turtles are endemic to the Australian continental shelf, and their hatchlings stay near the coast rather than drifting for years at sea like other species.

Which small rorqual was first described as a species in Nature in 2003, decades after it was first caught?

Omura's whale was named from eight whales taken by Japanese research vessels in the late 1970s plus a female towed to Tsunoshima in 1998; Wada, Oishi and Yamada published Balaenoptera omurai on 20 November 2003.

Sandy beaches near coral reefs are partly made of rock that which fish has chewed up and excreted?

Parrotfish bite off chunks of reef, digest the edible parts and excrete the rest as sand; a single fish can produce hundreds of pounds of it a year.

An octopus has three of which organ, one of which shuts down whenever the animal swims?

Hearts come in threes for an octopus: two serve the gills and a main one supplies the body. Because the main one idles during swimming, the animal tires fast and mostly crawls.

The male narwhal's spiral tusk, which can grow to three metres long, is actually an overgrown what?

The tusk is a canine tooth that grows out through the lip, and its millions of nerve endings make it a sensory organ as well as a showpiece.

Genetic and fossil evidence shows whales and dolphins are most closely related to which land animals?

Hippos are the nearest living kin of whales, which is why cetaceans are classed among the even-toed hoofed mammals despite their flippers and meat-eating habits.

When the breeding female in a group of clownfish dies, what does her male partner do?

The breeding male changes sex and takes her place, while the largest of the non-breeders below him matures into the group's new male.

Columbus's reported mermaid sightings in the Caribbean are widely thought to have been which sea mammals?

Manatees belong to the order Sirenia, named after the sirens of Greek myth, and they are closer kin to elephants than to any seal or whale.

Which animal, a likely source of the Norse kraken legend, was first photographed alive in its habitat only in 2004?

Giant squid tales were common among mariners for centuries, yet nobody obtained images of a living one in its habitat until a Japanese research team managed it.

Paul, an octopus at a German aquarium, won fame in 2010 by apparently predicting the results of what?

World Cup matches made Paul an oracle: he ate from one of two boxes decorated with team flags, and called all seven of Germany's games plus Spain's win in the final.

A shark's skeleton contains no true bone; what lighter, more flexible tissue is it made of instead?

Cartilage is durable yet only about half as dense as bone, which lightens the skeleton and saves a shark energy as it swims.

Dory, the forgetful fish in Pixar's Finding Nemo, belongs to which real species of reef fish?

Blue tang is Dory's species, an Indo-Pacific surgeonfish; online searches for it jumped for two to three weeks after the 2016 sequel, though imports of the fish did not rise.

The blue whale, the largest animal known to have existed, feeds almost entirely on which small crustaceans?

Krill are caught by lunge feeding: a blue whale charges a swarm with its mouth open up to 80 degrees, then squeezes the water back out through its baleen plates.

Drifting phytoplankton make up only about 1% of global plant biomass yet produce half of the world's what?

Oxygen output on that scale follows from the work phytoplankton do: these drifting cells carry out about half of all photosynthesis on Earth.

Reef-building corals get their colour from which tiny organisms that live inside their tissue?

Algae called zooxanthellae can make up as much as 30% of a polyp's tissue; a heat-stressed coral expels them, the event known as bleaching.

The songs of which marine mammal filled a 1970 album that became the best-selling environmental record in history?

Humpback whale songs reached producer Roger Payne through tapes a US Navy engineer made off Bermuda while listening for Russian submarines.

Which bird hunts by diving to depths of more than 500 metres, staying under for around 20 minutes?

Emperor penguin dives reach 535 m, and its bones are solid rather than air-filled, which spares it the pressure injuries most air-breathing animals would suffer.

The marine iguana, the only living lizard that forages in the sea, is found only on which islands?

The Galápagos Islands are the marine iguana's only home, and seaweed gathered from the sea makes up almost all of its diet.

Which animal, the largest living reptile, rides ocean currents to travel hundreds of kilometres along tropical coasts?

Saltwater crocodile journeys have been tracked by satellite: 8 of 20 tagged animals ventured into open ocean, and one covered 590 km of coast in 25 days.

Which seabird has the longest wingspan of any living bird, reaching up to 3.7 metres from tip to tip?

Albatross wings of the wandering species span up to 3.7 m, and some birds circle the Southern Ocean three times in a year, covering more than 120,000 km.

A larval flounder looks like an ordinary fish; what moves to the other side of its head as it matures?

One eye migrates across so that both end up on the side that faces upward, and which side that is depends on the species.

In open waters of the eastern Pacific, about three-quarters of deep-sea animal groups can do what?

Animals that produce light dominate the deep, yet in coastal habitats only about 2.5% of organisms are estimated to be bioluminescent.

Which fish, which may not breed until it is about 150 years old, has the longest known lifespan of any vertebrate?

Greenland shark pups are thought to spend 8 to 18 years in the womb, and the oldest adult studied was put at about 392 years, give or take 120.

Which fish, thought extinct for some 66 million years, was found in a catch off South Africa in 1938?

Coelacanth fossils run back more than 410 million years, and a second living species was discovered in Indonesian waters in the late 1990s.

Which shore animal's bright blue, copper-based blood is used to make a test for bacterial toxins in medicine?

Horseshoe crab is a misleading name: these animals are not crustaceans at all, but closer relatives of spiders, ticks and scorpions.

Which simple sea animals have no true tissues or organs and feed by drawing water through pores in their bodies?

Sponges lack a complex nervous system, yet they can still narrow their intake pores and shut the flow down when the water carries a lot of sand or silt.

Which Arctic whale is nicknamed the 'sea canary' on account of its high-pitched squeaks, squeals and clucks?

Beluga necks are unusually flexible too: the seven vertebrae are not fused, so the animal can turn its head sideways without rotating its body.

The baleen plates that filter-feeding whales use to strain food are made of which protein, also found in fingernails?

Keratin made baleen flexible and strong enough for corset stays, buggy whips and parasol ribs, sold under the misleading name whalebone.

Pearls are built from layers of which iridescent material, which also lines the inside of some mollusc shells?

Nacre, better known as mother-of-pearl, shimmers because its stacked mineral platelets are about as thick as the wavelength of visible light.

Which shellfish escapes its predators by repeatedly clapping its two shells together to jet through the water?

Scallop muscles are larger and better developed than an oyster's because the animal is an active swimmer, and some species even move en masse from one area to another.

Which crustacean spends its adult life fixed upside down by its forehead to rocks, ships and even whales?

Barnacle studies occupied Charles Darwin from 1846 to 1854, so intensely that his young son assumed all fathers worked on them at home.

European eels cross some 6,500 km of the Atlantic to spawn in which sea, named after its brown seaweed?

Sargasso Sea waters have no coastline at all: four ocean currents hem them in, making this the only named sea without land boundaries.

Which crustacean has the greatest leg span of any known arthropod, up to 3.7 metres from claw to claw?

Japanese spider crab adults live at depths of 50 to 600 m, and each moult takes about 100 minutes, during which the animal cannot move.

Which shore crustacean's males have one claw far larger than the other and regrow it after a moult if lost?

Fiddler crab males wave the oversized claw as if beckoning, which earned them the other name calling crab; a female's two claws are the same size.

Which fish clings to sharks, whales and turtles with a sucker that evolved from its first dorsal fin?

Remora grip works like a ratchet: sliding backward increases the suction, while swimming forward releases it.

Sea lions and fur seals differ from true seals in having which small but visible external feature?

Ear flaps give the eared seals their scientific family name, Otariidae, which comes from the Ancient Greek for 'little ear'.

Which jellyfish, among the largest known, was once recorded with tentacles about 36.6 metres long?

Lion's mane tentacles on that record animal, found off Massachusetts in the 19th century, stretched farther than a blue whale is long, and an adult carries around 1,200 of them.

Which eel-shaped scavenger fish defends itself from predators by releasing copious amounts of slime from its skin?

Hagfish slime clogs an attacker's gills, and the hagfish cleans itself afterwards by tying its body in a knot and sliding the knot from head to tail.

Which fish, the world's longest bony fish at up to about 8 metres, may lie behind many 'sea serpent' sightings?

Giant oarfish are also nicknamed 'earthquake fish' from a popular belief that they surface before tremors, though no such link is supported.

Which objects does the veined octopus, a tool user of tropical Pacific waters, gather and use for shelter?

Coconut shells gave this octopus its other common name, and it has been seen walking on two arms while using the other six to disguise itself.

A 'mermaid's purse' is the colloquial name for what, produced by some sharks, skates and chimaeras?

An egg case of this kind surrounds the developing young, and catshark cases have long tendrils at the corners that anchor them to structures on the sea floor.

Which fish, armed with venom glands at the base of its needle-like dorsal spines, is the most venomous known?

Stonefish take their name from grey, mottled camouflage the colour of a rock, and a sting can kill a person if it goes untreated.

Each year millions of land crabs march to the sea to lay their eggs, closing roads, on which Indian Ocean outpost?

Christmas Island once held an estimated 43.7 million of the adult crabs, before the accidentally introduced yellow crazy ant cut the population by about a third.

Which large starfish, covered in venomous spines and bearing up to 21 arms, preys on the polyps of hard corals?

Crown-of-thorns sea star spines recall the biblical crown, and its body bends and twists to fit the contours of the coral it feeds on.

Which marine mammal holds the records for both the deepest recorded dive, 2,992 metres, and the longest, 222 minutes?

Cuvier's beaked whale dives are routine feats too: typical foraging trips go below 800 m and last 30 to 90 minutes, with only a few minutes at the surface between them.

Which giant relative of the dugong, described from the Bering Sea in 1741, was hunted to extinction within 27 years?

Steller's sea cow was first met by naturalist Georg Steller when his expedition was shipwrecked on Bering Island; slow and easily caught, it was killed for its meat and hide.

Despite its menacing name, the deep-sea vampire squid lives mostly on which drifting food?

Marine snow is debris sinking from the waters above, and the vampire squid gathers it with two retractile filaments instead of the feeding tentacles other squid use.

The deep-sea 'zombie worms', which have no mouth, feed by dissolving their way into which unusual food?

Whale bones are dissolved with acid secreted from root-like tissue, and the worms were found on a decaying gray whale 2,893 m down in Monterey Canyon.

Dolphins focus the clicks they use for echolocation through which organ, a sound lens in the forehead?

The melon refracts outgoing sound into a focused beam and matches it to the surrounding water, so the clicks leave the head with the least loss of energy.

Which fish, also called the moonfish, is the only one known to keep its whole body warmer than the sea?

Opah body heat is not held steady as a mammal's is: it stays above the level of the surrounding water but still rises and falls with it.

Which fish, barely half a metre long, gouges round plugs of flesh from whales and has left its marks on submarines?

Cookiecutter shark bite marks have turned up on undersea cables and human bodies too, and its victims include animals as formidable as the great white.

Which venomous Indo-Pacific fish, popular in aquariums, has become a significant invader of the Caribbean Sea?

Lionfish control has taken odd turns: park officials in Honduras tried training sharks to eat them, and divers in Florida and Texas are encouraged to catch them for food.