Bright Guy

Cool facts on just about everything

Aquatic Biology


  1.  An experiment found that the archerfish could recognise human faces!  This fish, known for spitting streams of water to knock bugs into the water, can recognise a  human face with 80% accuracy!  This is the first time fish have been shown to have this ability.
  2. The horseshoe crab are 'living fossils', extant for at least 450 million years!  They have numerous 'eyes' including two compound lateral eyes, a pair of median eyes for visible and UV light, a single endoparietal eye, a pair of rudimentary lateral eyes on the top, a pair of ventral eyes near the mouth, 5 additional eyes on the top of its shell and photo-receptors on the telson!  Unlike vertebrates, with hemoglobin, they use hemocyanin.  This means that instead of using iron molecules to transport oxygen (making our blood red), they use copper, making their blood blue!  Their blood also contains amebocytes which defends against pathogens.  This substance is used in medical applications to detect bacterial endotoxins, meaning some of their blood is harvested.  Unfortunately this leads to a mortality rate of 3-30%.

  3. Infant humpback whales in their early life are quite active, often breaching or flying out of the water, dozens of times in a row.  Now researchers have found that this incredible expense of energy (equivalent to about 200 L of milk per day) is because this exercise produces myoglobin, an oxygen-carrying chemical in muscle.  This allows for longer breath-holding and longer dives and may also help survive killer whale attacks.
  4.  Greenland sharks can live up to 400 years of age!  They only grow about 1 cm a year (reaching sexual maturity at 150).  They beat the former record holder of a bowhead whale estimated to be 211.  Historically, fish-ages were determined but sectioning otoliths (tiny stones) in their ears and counting the concentric rings laid down, similar to tree-rings.  However, sharks are cartilaginous and have no bones.  Therefore a different strategy, used by dating certain proteins contained within the shark's eye lens.  They are inert at birth and therefore can be radiocarbon dated to provide an approximate age.
  5. 10 meter long, multi-tonne crocodile fossil has been found in Tunisia.  Living 130 million years ago it likely fed on marine turtles able to easily crush their shells.  This animal, Machimosaurus Rex, was the largest and last of a large group of ocean-going crocodiles.
  6. The Devils Hole pupfish is only found in Devils Hole, a 33 C geothermal sinkhole located in the middle of California's Death Valley.  The fish (claimed to be the rarest in the world) only lives in this small pool.  They survive by scraping algae off the walls of the pool.  New research suggests the fish have only been isolated from its genetic relatives for a few hundred years.  This means, somehow, the fish crossed hundreds of km of desert to colonize this pool.  Theories include this happened during a catastrophic flood or perhaps that eggs were carried along the feet of birds.
  7.  Geographic cone snails have been observed using a cloud of insulin to stun fish!  Already one of the most venomous animals on the planet, before they use that venom, they use a toxic cloud which includes insulin.  This insulin (different from the snail's own insulin) passes through the gills of their prey, drops their blood sugar, and allows the snail to eat them.
  8. When attacked, damselfish, release chemicals that attract more predators.  The ensuing frenzy provides the damselfish with a 40% chance of escape (versus only 5% without the frenzy).
  9. Manta rays have the highest brain to body mass ratio of all fish.
  10. Limpets teeth are the strongest biological material, EVER!  Their tongue is bristled with tiny teeth which scrape food off rocks and into its mouth.  It's 5x stronger than spider silk.  Its fibers have been found to be tightly packed and include iron-based goethite.  If one was the thickness of a spaghetti noodle, it could hold 1500 kilograms (3,300 lbs)!
  11. Animals first had sex in a Scottish lake!  Study of fossils of Microbrachius dicki noted an L-shaped appendage on males while females have a small bony structure that appeared to lock in the male structure.  This suggests they're the first species to have stopped reproducing by spawning and have sex.  The first sex-position would have been side-by-side (like square dancing).  The fossil record suggests fish ultimately reverted to spawning before copulation returned in sharks and rays.
  12. Birth control pills are feminising fish!  Wastewater containing oestrogen (from birth control pill use) is spilling into waterways.  This hormone is interfering with fish reproduction because male fish (fatheads) begin to produce egg yolk and, ultimately, eggs!  This is leading to a crash in the population (an important food source).
  13.  Groupers and Eels have been observed teaming up to catch prey!  It was thought only humans and chimpanzees behaved in this way however the red grouper was observed attracting the attention of an Eel by shaking its head.  They then swim off as a team with the grouper swimming above the reef while the eel swims through it.  This increases their success of catching prey.  Groupers were found learning which eel was the superior partner.  The researchers' study consisted of using a fake "helpful" and "unhelpful" eel (it would swim in the wrong direction).  The grouper was therefore observed returning to the helpful one.
  14. Ming, the nickname given to an ocean quahog clam, dredged off the coast of Iceland is thought to be the oldest individual (non-colonial) animal ever discovered.  Born in 1499, it lived for 507 years, dying in 2006.
  15. Tardigrades can be cooked (122 C in an autoclave), frozen (to -272), crushed (to almost 6000x atmospheric pressure), dried, or sent to space for years and still survive!  Measuring 1-1.5 mm there are more than 900 species.  They've been found in the Himalayas, Japanese hot springs, in Antarctica and at the bottom of oceans.  They can enter a form known as a "tun" (pictured right) where their metabolism slows to 0.01%, they curl into a dry husk.  Their cells are stabilized by creating trehalose, a sugar forming a glass-like state inside their cells to protect key components.  Then when they dry, they produce excessive antioxidants to prevent DNA damage.
  16. Fish have been discovered living below the Whillans Ice Stream, a glacier in Antarctica that's 2,428 ft deep!

  17. The mysterious (and bizarre) function of the lower jaw of the Helicoprion has recently been discovered.  The lower jaw rotates similar to a circular saw.  It rotates 1/4 turn from front to back as the jaw opens and closes.  It had permanent teeth (unlike sharks) suggestive that they ate soft, squishy organisms, such as calamari.  It's now estimated to have been as much as 7 meters in length.
  18. Plankton is responsible for about 50% of the oxygen that we breathe.
  19. A juvenile eel is called an elver.
  20. Bdelloid rotifers are small, freshwater, creatures that have been around for over 300 million years and are exclusively female.  Biologists have considered this an evolutionary mistake because of the lack of genetic variation.  This animal has solved this problem by stealing the DNA from organisms they ingest.  About 10% of their genes have been "stolen".
  21. Adult male killer whales have been found to do better when supported by their motherLike humans, killer and pilot whale females live into menopauseResearchers believe these older mothers support their male offspring to ensure their genes are passed on.  They don't support their daughters because, as a pod, this support is intrinsic, however males only reproduce with females from other pods.  Seeking out these females takes time and expends energy.  With their mother's support, they can remain competitive among other male whales.
  22. Bowhead whales live entirely in the Arctic ocean and are kept warm by 40 cm of fat.  This particularly thick fat layer and lack of a dorsal fin put it at risk of overheating.  Recently, the function of a massive organ, very similar to the mammalian penis, dubbed the "corpus cavernosum maxillaris" on the roof of the whale's mouth, has been found to engorge with blood when the whale is hot and allow the whale to cool off by allowing water to flow into its mouth.
  23. Sand Tiger Sharks have two uteri and, therefore, give birth to two pups at a time.  Recently it's been discovered that these two surviving embryos will have cannibalized their siblings (embryonic cannibalism).  By killing them before they're born, the surviving two can grow to a much larger size (almost a metre in length).  The eyes and teeth are some of the earliest features to develop on the embryo facilitating this process.
  24. Food passes through the giant squid's brain on the way to its stomach.
  25. When killer seaweed (Acropora nasuta) touches spiky coral; the coral releases a compound that prompts goby fish to seek out and trim back the seaweed.  Both broad-barred goby (Gobiodon histrio - pictured) and redhead goby (Paragobiodon echinocephalus) responded to the compound.
  26. 1/2,000,000 lobsters are blue because they are unable to produce the red carotenoid molecule.  Lobsters can also be yellow and white.  While often found on display, the meat is all the same.
  27. Micronecta scholtzi is a 2 mm long water bug that produces the loudest sound/body size, about 105 decibels (like a jackhammer).  It makes this sound using its penis; by rubbing it against its belly!  Most of the sound is lost in the transition from water to air.

  28. Scientists have calculated that there are 8.7 million species (only 10% of those have been discovered).  Hypothetically, it would take 300,000 taxonomists 1,200 years and cost $364 billion to study the estimated:
    • 6.5 million on land
    • 2.2 million in the ocean
  29. Elysia chlorotica is a 3 cm slug that lives off the Eastern coast of North America.  The slug can photosynthesize!  Like plants, it uses the sun's energy to convert carbon dioxide into sugar.  It does this by ingesting algae and incorporating the plant's chloroplasts into their own cells.  They can survive their entire 10-month lives by solely using sunlight!


  30. Turritopsis dohrnii  (the immortal jellyfish) can transform from an adult back into a juvenile state!  The jellyfish (the size of a pinky fingernail), when damaged, starving or facing another type of crisis, transforms all of its existing cells to a younger state.  This "polyp colony" can develop into hundreds of clones.  Consequently, the jellyfish is invading most of the world's oceans.
  31. A fish's age can be determined by the number of growth rings on its scales.
  32. The bizarre shape of the head of hammerhead sharks provides the fish with greater stereo vision (depth perception).  The eye placement of the 9 species facilitates 360-degree vision.  Their heads also function as receivers when receiving electrical signals.
  33. Male Anglerfish are very small and cannot survive in the deep ocean alone.  Their entire lives are spent finding a mate.  They then permanently attach themselves to the female fish and become absorbed by her body!
  34. Killer whales and pilot whales are, by definition, dolphins.
  35. Spinning dolphins spin in midair when they jump out of the waterThis is a social behaviour, similar to a dog's wagging tail.
  36. Candiru (toothpick fish) live in the Amazon.  They are attracted to the urea and ammonia of urine.  They insert into the urethra and secure themselves with spines and feed off of the person's blood.  They must be surgically removed.

  37. Elephant seals can hold their breath for 120 minutes (the longest of any non-whale) and dive 1.5 km!  Males are 10x the size of females.  They have been observed taking 'power naps' at depth.
  38. Sea otters have the densest fur of any other animal.
  39. The platypus is 1 of only 2 mammals that lay eggs.  It uses its bill to crush food.  When swimming underwater, it closes its eyes and detects its prey using electroreception (similar to sharks).  To feed it's hatched egg, milk oozes from its skin like a sweat rather than from a nipple.  Males have a venomous claw on their hind feet, and they have no stomach! 
  40. It's believed frogs learned to jump before they learned how to land.  While some species have now perfected this skill by tucking in their legs in mid-leap, others, such as the rocky mountain tailed frog, have not.  They perform what most would describe as a 'belly-flop'.
  41. New research found the archer fish, endemic to South-East Asia, uses external fluid dynamics (rather than its muscles) to form the stream of water that shoots down prey up to 2 meters away.  They make a stream by pressing their tongues against a special groove in their mouths forming a gun-barrel. 
  42. Bearded gobies are a 6" fish that are saving the ecosystem off the coast of S. Africa.  Overfishing of sardines in the 1960s caused a collapse in the ecosystem creating a dead zone populated by jellyfish with a soil bed laden with toxic deposits.  These fish can live in low oxygen, eat jellyfish and marine worms (found on the sea floor).  By filling the niche left behind by the sardine population, the ecosystem is beginning to recover.
  43. Hooded seals have the shortest nursing period, only 4 days.  The pups are then left to fend for themselves.
  44. Right whales have the smallest brain to body ratio compared to all other whales.  Meanwhile, they have the largest testes of the animal kingdom weighing upwards of 1 tonne!  They can produce gallons of sperm and have a penis that is 12 feet long and completely mobile.
  45. Lake Nicaragua is the only fresh water lake with a species of freshwater Bull Sharks.
  46. Male Bluestreak cleaner wrasse, a cleaner fish, will punish their female partners if they do something to offend the fish being cleaned.  If females take a bite of the client's skin (rather than eat only the parasites) for a larger meal it offends the client and it will swim away.  The male Bluestreak fish, losing its source of food, will aggressively chase the female away.

  47. The mantis shrimp has the best vision, ever.  Their eyes are divided into 3 parts giving each pupil stereo vision (see depth with one eye).  Unlike us, who have 3 photoreceptors, they have 16.  They can see in UV and polarized light giving incredibly crisp vision underwater (unlike our fuzzy vision).  When sparing, one male will "punch" another using a muscle in its forearm to cause its exoskeleton to build energy and send out a shot that's faster than a gunshot.  The opposing male uses its tail as a punching bag, blocking the shots.
  48. The pistol shrimp has specialised claws that allow it to make a 'snapping' sound so powerful that the cavitation bubble produces temperatures of 4,700 C (the sun is 5,500 C)!  This kills its prey.  It competes with beluga and sperm whales as the loudest animals in the sea.
  49. Lungfish can breathe both above and below the water.
  50. Dolphins can recognise themselves in a mirror and have been observed using sponges as tools to get fish out of coral.
  51. Sea Urchins reproduce via a process called "fissiparity" which means they divide themselves in two.
  52. The Bornean flat-headed frog has no lungs instead breathing through its skinThough common in amphibians, this has never been observed in frogs.  The frog is often found in cold, fast-flowing water facilitating highly oxygenated water making contact with its skin.
  53. The Amazon Molly is an all-female species of fish that lives in the southern US and northern Mexico.  The female lays diploid eggs (not requiring male sperm) meaning that the offspring are clones of the female.  Oddly, to reproduce, females require a male presence (even one from another species).  Rarely, Amazon Molly males are found, they are triploid (pictured, male on the bottom, female on top).
  54. It is common for the pearlfish to live in the cloaca of sea cucumbers!  This provides them with a safe place to live whilst gaining nutrients as the sea cucumber eats and defecates.
  55. Sea-grass in the Mediterranean Sea has been found to be tens of thousands of years old! A study of samples of Posidonia oceanica found genetically identical samples from an area of about 15 km. This particular species can reproduce both sexually and asexually. This is the first time that genetic material has been found to survive for such a long period of time through asexual reproduction, challenging the original theory that small 'copy-errors' hindered the longevity of the genetic material.
  56. Research has found that the beluga whale can imitate human voices.  It began in 1984 when people noticed unusual sounds in the vicinity of a whale and dolphin enclosure.  It was found that the sound was from a white whale named Noc.  Unlike humans, who use the pharynx, whales use their nasal tract and make muscular adjustments to their vestibular sac.  An audio sample can be heard here: 

  57. The closest living relative to whales are hippos.  Both evolved from the same animal about 50 million years ago.
  58. Daphnia Pulex, a water flea as big as '=', has the most genes of any other creature, 31,000 (humans only have 23,000).  These fleas have an ability to adapt to sudden changes in their environment and is one of the few tiny animals capable of producing hemoglobin.  Due to its ability to change quickly, scientists believe they can analyze them to determine the true state of the ocean in which they are found.
  59. The Leatherback turtle is the largest species of sea turtle capable of diving to depths of 4,200 ft (1,280 m).  Its fins can grow up to 2.7 m.  The largest specimen discovered was 3 m in length and weighed 916 kg (over 2000 lbs).  They are critically endangered.

  60. Veined octopuses collect coconut shells, empty them, and assemble them into a spherical hiding spot!  This is the first time invertebrates have been observed using tools.  Octopuses are known for their good vision and intelligent brain.  They have 3 hearts (2 that pump blood through the gills and 1 that pumps blood everywhere else).

  61. The moray eel bites its food, then a second jaw located in the throat pulls the food down to swallow!  This is believed to be a modified hyoid bone.

  62. Green turtles lay about 18,000 eggs in their lifetime!

  63. The largest freshwater fish caught in Thailand was 660 lbs.  The Mekong Giant Catfish measured 3.2 m (10.5 ft).   The species is critically endangered.
  64. Crocodiles cannot stick out their tongue.
  65. Tiktaalik (an Inuit word meaning 'large river fish'), an extinct fish from the late Devonian, was discovered in Nunavut, Canada.  The fish has four features similar in skeletal structure to crocodilian appendages.  It had lungs, gills, and is the first fish to have a 'neck'.  They are an intermediate between fish and amphibian.
  66. Jewel fish tuck their babies into bed!  The parents work as a team to round them up and get them into the nest each night.  The father normally does the rounding and the mother keeps them in the nest.
  67. In its lifetime, a shark can lose as many as 24,000 teeth!
  68. Blue Whales are the largest animal to have ever existed.  Their tongue is as heavy as an elephant.  Their lungs are 500x larger than ours.  Their heart is the size of a small car which drives 10 tonnes of blood through millions of kilometres of capillaries and beats 2-3 times per minute.  In one bite it can consume up to 1 tonne of krill.  In some places, it has fat that is 20" thick.  It can hold its breath for half an hour and dive to depths of over 500 feet.
  69. Dolphins and whales sleep with only one eye open.  Scientists believe that this is because they are watching for predators or because only 1 hemisphere of their brain sleeps at a time.

  70. Some frogs have a natural antifreeze in their blood that allows them to completely freeze during the winter and thaw the following spring.  This occurs while buried in the mud at the bottom of a body of water.
  71.   The Cockeyed Squid, Histioteuthis heteropsis, lives deep in the Pacific ocean's 'twilight zone', just before light disappears completely. The squid has two very different eyes.  One is flat and black and mostly looks down to keep an eye out for high-contrast flashes of bio-luminescence.  It's unusual, yellow eye looks upwards.  It's been found to have increased sensitivity to the faint sunlight above.  It's yellow colour filters out the blueness of the ocean which makes prey easier to detect.
  72. Starfish can regrow severed limbs through fragmentation.  The remaining arm (as long as there is some of the middle portion) can actually grow into an entirely new starfish.  It can do all this without a brain!

  73. The sailfish can reach speeds of up to 115 km/h.  When they attack they have vertical blue lines that appear on their sides which confuse its prey who typically see in the blue and ultraviolet spectrum.
  74. Australian box jellyfish has the deadliest venom of any animal!  There are two recorded deaths from this species where the jellyfish was the size of a thumbnail!  This particular species of Jellyfish also has 20 eyes.

  75. Female whales can loose 1/3 to 1/2 of their body weight when menstruating!
  76. Triops cancriformis (horseshoe shrimp) is an endangered species that is considered to be the oldest extant animal species on Earth!  ~200 million-year-old fossils have been found demonstrating the species has been virtually unchanged.  The population is currently limited to the Caerlaverock Wetlands in Scotland and a pond in the New Forest in Southern England.
  77. The largest creature without a backbone is the colossal squid, which can grow up to 60 ft and weigh as much as a tonne!  They have the largest eyes in the animal kingdom (as much as 40 cm across) which, unlike ours, have no blind spot.  This picture is a 17 ft female squid.
  78. Sperm whales are the deepest diving whale at 2 km and recently have been found to have regional dialects.  They have the largest brains of any species.

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