50 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; a female keeps travelling and hunting with her pod for decades after her last calf.

'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 reinforced with goethite, an iron mineral, and tested at a tensile strength of up to 6.5 GPa, beating spider silk's 4.5 GPa.

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

A stomach is missing from the seahorse's extremely simple gut, so food passes through fast and it must keep feeding to stay alive.

Which fish was filmed in 2023 at 8,336 m in the Izu–Ogasawara Trench, deeper than any fish had been seen before?

A snailfish took the record from earlier snailfish filmed at 8,145 m and 8,178 m in the Mariana Trench in 2014 and 2017; the deepest species have no swim bladder, so they do not burst when raised.

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

Its fat is green from a diet of seagrass, lying in a layer between the organs and the shell, while the carapace 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.

How many eyes does a box jellyfish have, set in clusters on four sensory structures called rhopalia?

24 eyes in total sit at the ends of sensory structures called rhopalia, which are wired to the jellyfish's ring nerve.

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

The sea urchin's entire chewing apparatus carries the name because Aristotle described it in his History of Animals, in a passage later translated by D'Arcy Thompson.

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

Its snout, or rostrum, is lined with transverse teeth that turn it into a saw, and sawfish are rays rather than sharks despite their shark-like build.

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 280-kg bluefin tuna for a record 333.6 million yen in January 2019?

Tokyo's new-year auction is a publicity contest, which is why the 280-kg Pacific bluefin went for about US$3.1 million on 5 January 2019, far above its market value.

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, head just below or at the surface or pointing straight down, a habit researchers have watched in whole pods.

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 sunfish, was found dead in 2021 off which Atlantic islands?

The Azores fish was a Mola alexandrini, a species that reaches 3.3 m; it beat the previous record, a 2,300-kg sunfish caught off Kamogawa, Japan, in 1996, by nearly half a tonne.

Which sea turtle's flexible carapace is built to withstand the pressure of dives to about 1,200 m?

Leatherback turtles have a carapace of unique design, and the flexible skin over it may let them grow and shrink insulating stores for deep dives and long migrations.

Human eyes carry four types of photoreceptor cell; a mantis shrimp's eyes have up to how many?

16 types at the top of the range (12 at least) let mantis shrimp see from deep ultraviolet to far-red and also detect polarised light.

The naval torpedo took its name from a genus of which fish, itself named from the Latin for 'numb'?

Electric rays of the genus Torpedo deliver a shock that leaves the victim numb, which is what torpidus means; the weapon simply borrowed the fish's 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 whale shark caught in 1996 carried roughly how many pups, proving whale sharks bear live young?

300 or so pups in one female showed that whale sharks are ovoviviparous: the eggs hatch inside the mother and the young are born live.

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, or a 'smuck', is the collective noun; jellyfish are built mostly of mesoglea, a jelly that is 95% or more water with collagen fibres.

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 box jellyfish, cause which illness, named after an Aboriginal people?

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

Guinness lists which fish as the slowest swimmer, with a top speed of about 1.5 metres an hour?

The dwarf seahorse, Hippocampus zosterae, lives in shallow seagrass beds of the Bahamas and the southern United States and creeps along at barely 5 feet an hour.

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

South Australia adopted the 'leafy' as its marine emblem, and divers see them near Adelaide at Rapid Bay, Edithburgh and Victor Harbor.

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 the longest animal ever reported?

The bootlace worm described by William M'Intosh outstretched the longest known lion's mane jellyfish; typical specimens run 5–15 m, and the 55 m figure may reflect a stretched body.

Which Indo-Pacific cephalopod walks the seabed on its arms and is one of just three cephalopods known to be poisonous?

The flamboyant cuttlefish ambles on its lower arms while rippling the membranes along them, and a toxicology report found its muscle tissue highly toxic.

Which deep-sea species props itself up on the seabed on stilt-like fin rays, each up to a metre long?

The tripod fish, Bathypterois grallator, stands on elongated pelvic and tail-fin rays that carry no sensory cells and can reach three times its body length.

The pistol shrimp rivals the biggest whales as the sea's loudest animal; what actually makes the bang?

A bubble collapsing off its claw makes the snap: the claw shuts so fast it forms a cavitation bubble, and the pop peaks at 218 decibels, enough to stun 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 depths of 283–439 m in that corner of the Caribbean, and the type specimen was an 18.2-cm female.

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.

The Pompeii worm, living in vent water of 45–60 °C, is the most heat-tolerant complex animal after which creatures?

Tardigrades alone beat Alvinella pompejana, which survives 105 °C for short spells thanks to heat-resistant collagen and a coat of symbiotic bacteria.

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 did three Japanese scientists first describe 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.