There are aliens, of a kind, among us.
Some creatures on our wild, wonderful planet are so strange, they could just as well have come from outer space.
One kind of sea slug can separate its head from its body, and then shuffle away, to regrow itself in its entirety. (Read Have you lost your head? alongside)
Sharks evolved so long ago, they predate our current North Star. (There’s more on that alongside too.)
Tardigrades are microscopic invertebrates that can survive boiling water, freezing temperatures, radiation and even a space vacuum, by entering a dormant state. They have no lungs or heart, and survive by absorbing oxygen through their bodies.
Crocodiles have not really changed their biology in over 240 million years. Their ability to slow their metabolism and thus manage for long periods on very little food helped them survive the fallout of the Chicxulub impactor.
Plenty more wondrous species are still being discovered, and we’re learning more about even the most familiar ones. How, for instance, do some jellyfish live out their lives, shrink to a blob-like cyst… and then simply start over?
“Compromising more and more of these creatures’ habitats without yet understanding what we are losing is a profound tragedy,” says Greg Rouse, marine biologist at the Scripps Institution of Oceanography in California. “They hold vital clues to our world and how we got here.”
From a sea slug that steals from algae to perform photosynthesis as an animal, to a fish whose DNA hasn’t changed in over 150 million years, a tree that can live for millennia and resist fire, and a sort-of reptile with a third eye, we’re celebrating some of our strangest, most wonderful co-habitants on Earth, to mark World Environment Day.
* OLDER THEN TREES, OLDER THAN THE NORTH STAR: THE GHOST SHARKS
The Australasian narrow-nosed spookfish or ghost shark, newly identified in 2024, has a lineage so ancient, its ancestors existed before our current North Star (Polaris, which assumed mass 50 million years ago).
It existed before the first trees evolved, before dinosaurs and flowering plants. It was around, in fact, as far back as 375 million years ago.
It’s small, for a shark; only about 3.5 ft long.
What has helped it survive is its ultra-slow metabolism, which lets it conserve energy in the deep seas; and its trademark long snout, filled with sensory pores that detect hard-to-find crustaceans and molluscs to feed on.
Because it has always lived in deep-ocean environments, it remained largely immune to catastrophic events such as ice ages and the Chicxulub impactor, says Brit Finucci, a fisheries scientist with New Zealand’s National Institute of Water and Atmospheric Research, who led the team that discovered the species.
“The snout is especially striking,” she adds. “Particularly in young individuals, it can account for up to 50% of their total body length.”
The scientific name the species has been given, Harriotta avia, is a tribute to its longevity. Harriotta was Finucci’s grandmother’s name and avia is Latin for grandmother. Because, as she puts it, these small sharks are grandmothers of the sea.
* AN ANIMAL GREEN FROM PHOTOSYNTHESIS: THE LEAF SHEEP
This tiny sea slug — each one about the size of a grain of rice — was discovered near Japan in 1993 and is one of the only animals in the world capable of photosynthesis.
It cannot by itself turn sunlight into food. But it can steal chloroplasts from algae, which it then uses to turn sunlight into energy, whenever algae itself becomes scarce.
The leaf sheep (Costasiella kuroshimae) gets its name from the fact that it grazes in ways that keep algal levels balanced in marine water bodies.
This advanced, highly specialised species lives in intertidal zones near coral reefs in Japan, Indonesia and the Philippines. The stolen chloroplasts also give it its green, leafy appearance, which helps it blend into the algae too, camouflaging it from the small reef fish that are its predators.
* HAVE YOU LOST YOUR HEAD? : THE ELYSIA SLUG
If you think the leaf sheep is remarkable, well, another sea slug takes things distinctly further.
The Elysia marginata can detach its head from its body and then simply shuffle away, just a blob with tiny antennae, as it regrows itself in its entirety: heart, intestines, reproductive organs and all.
In the interim, the slug survives by nibbling on algae. Digestive glands attached to the head, and stem cells in the neck, make the remarkable regeneration possible.
This mechanism likely evolved as a way to survive parasitic infections, marine biologists say.
In something a bit out of a horror movie, the bodies left behind can live on too, sometimes for months, using chloroplasts, like the leaf sheep, to sustain themselves via photosynthesis, until they eventually pale, weaken and die (since they can neither eat nor ingest more chloroplasts).
* 25-FT TALL BOUQUETS : THE TALIPOT PALM
In December 2025, an unusual spectacle drew crowds in Rio de Janeiro. In a true swansong, palms planted in the 1960s bloomed for the first and last time.
There are other plants that do this, blooming just once before they die; but none does it quite so dramatically.
The talipot palm (Corypha umbraculifera; native to the tropical regions of Asia, Sri Lanka, southern India and the Western Ghats) has the largest flower cluster in the world: a 25-ft-tall bouquet that grows in tall tufts. These erupt from the top of the crown and take the height of the average tree from about 80 ft to over 100 ft, with all that additional height made up of millions of tiny yellow blooms. (It’s no wonder the crowds gathered.)
This spectacle occurs once every 30 to 80 years, after which the tree takes a year to produce its fruit, and proceeds to die. It has been doing all this for about 80 million years.
* A ‘LIZARD’ WITH A THIRD EYE: THE TUATARA
These odd creatures (the only survivors of the ancient and diverse order Rhynchocephalia) have jaws that slide back and forth, a third eye on the tops of their heads, and barely breathe, sometimes taking just one breath in 70 minutes.
They can live for more than a century, thrive in cold climates, and are found only in New Zealand. The third eye is believed to regulate circadian rhythms and help absorb UV rays. As they age, it falls out of use and becomes covered by scales.
They look like reptiles but aren’t reptiles. They are, in fact, a strange pastiche of attributes.
A 2020 study by Neil J Gemmel of the University of Otago, New Zealand (published in the journal Nature), found that their longevity is aided by a genome that is highly repetitive, representing what is in essence a robust toolkit that can help slow ageing, boost immunity, and aid in healing and cell repair.
Scientists are still unlocking the secrets to the tuatara’s make-up, but they might want to hurry. Rising temperatures could further skew the hatchling sex ratio towards males, eventually driving this ancient survivor extinct.
* HIROSHIMA SURVIVOR : THE GINGKO TREES
It’s hard to know where to begin with this one.
These giants can grow to 80 ft in height and as much as 40 ft in width.
Some have been alive for 3,000 years.
The Ginkgo biloba has survived numerous extinction cycles and ice ages, over 270 million years. What’s helped is a DNA that is mindbogglingly complex.
When its genome was fully mapped in 2016, it was found to contain 10.6 billion DNA “letters”. By way of comparison, the human genome contains about 3 billion letters.
As it evolved these variations, the tree found ways to protect itself. It has, for instance, a kind of insecticide bark that doesn’t just produce chemicals that repel or poison a pest (many plants do that). This one can also, at the same time, release a set of compounds that will attract the specific pest’s predators.
Ginkgos are resistant to urban pollution, and to fire (flavonoids and phenolic acids limit cellular damage should the bark be scorched). Their leaves are thick and retain water, which helps them resist flames too. Some even survived the Hiroshima bombing of 1945.
They’re more incredible than the Ents JRR Tolkien dreamt up, in The Lord of the Rings.
* FERRARI OF THE SEAS : THE CHIMERA MANTIS SHRIMP
Discovered in 2024 off the coast of Western Australia (and also found in Japan), the chimera mantis shrimp (Incertasquilla chimera) packs a punch so severe, it can have an impact comparable to a .22-calibre bullet.
Not only do they punch, they skewer too. Their large, spiny claws can grow to take the shape of a hatchet, hammer or spear, depending on the environment and prey. But the primary weapon is the strike — and a pair of eyes that can move independently, watching for predators and encroachers to smash at too.
The force isn’t technically overkill. Without it, there would be no way for this 3.5-inch creature, nicknamed the Ferrari of crustacean world, to get a meal, since it dines primarily on hard-shelled molluscs, crabs and oysters.
* ROCK ‘N’ ROLL: THE ELVIS WORM
Wearing a shimmering armour of iridescent scales, the Peinaleopolynoe elvisi (named after Elvis Presley) was discovered in 2022, on the carcass of a whale.
The sequinned jumpsuit is a bit of an attention-seeking gambit, as with the original rockstar. These bacteriovores, about the size of a thumb, live about 13,000 ft underwater, and scare off predators, defend territory and compete for mates using the flash of these scales. (A flash, incidentally, that is dependent on the bioluminescence of other sea creatures, since there is little natural light at these depths.)
Elvis worms typically live on volcanic seamounts and in hydrothermal vents, snacking on the bacteria that feed on the methane that bubbles up from the seabed at such fissures.
Some Elvis worms have been found with chipped scales, marine biologists say, because they are fierce, showy fighters who bounce around each other in territorial battles, throwing punches and even aggressively biting chunks out of each other with their powerful jaws.
* A FISH IN DEEP FREEZE: THE GAR
For 150 million years, a group of species derided by anglers as “trash fish” (because they’re too bony to eat, and eat fish that are delicious) have stayed precisely the same, a rare consistency not seen even in sharks.
Across all that time, the gar, which looks like a cross between a fish and an alligator and is shaped somewhat like a torpedo, has seen DNA and RNA change up to three orders of magnitude more slowly than any other major group of vertebrates, including living fossils such as the coelacanth.
Its DNA is so strong, in fact, that it can still procreate by hybridising, or fertilising the eggs of other gar species.
Molecular mutations are so rare that studies indicate they amount to only 0.00009 mutations per million years (compared to 50 to 100 mutations between parents and their newborn, in humans). At rates this low, DNA can correct every alteration in the gar, acting as a sort of expert proof-reader, neutralising genetic abnormalities.
With its elongated snout and needle-like teeth, this is essentially a fish frozen in time.
* BRAINLESS WONDERS: THE JELLYFISH
They’re so common, we don’t think much of them. And yet jellyfish have existed in more or less the same shape for more than 500 million years.
In a sort of cosmic elegance, what has helped them do this is their simplicity.
“Jellies have no need for a stomach, intestine, or lungs: nutrients and oxygen slip in and out of their cell walls,” Allen Collins, affiliate research zoologist with the National Oceanic and Atmospheric Administration Fisheries, a curator at the Smithsonian Natural History Museum, writes in the Smithsonian Ocean Portal. “The outer cells that make up the epidermis contain a loose network of nerves called the “nerve net” which doubles as a brain, helping them detect change in the environment… This is the most basic nervous system known in a multicellular animal.”
Between these layers is a gelatinous substance that contains some structural proteins, muscle cells and nerve cells, forming a kind of internal skeleton.
With all their simplicity, they can also be huge, and deadly. The largest known species, Lion’s Mane, has a bell that can grow to a diameter of 7 ft and tentacles that can stretch 120 ft long. Jellyfish typically pack quite a punch too, using neurotoxins to debilitate prey.
Scientists, meanwhile, are still studying what makes some age in reverse. And how some manage to live out their lives, shrink to a blob-like cyst, and then simply… start over.
