Scuba diver instructor Gregor Irvine was lucky enough to film this ribbon-like creature cruising in clear waters around Indonesia's Lembeh Strait late last year. Flatworms are soft-bodied invertebrates that are found pretty much anywhere there is moisture. With no body cavity or specialised respiratory or circulatory organs, flatworms rely on diffusion to acquire their oxygen. Their flattened shape helps allow more nutrients and oxygen to pass through their bodies.

Flatworms are a diverse group. There are over 20,000 known species, from tapeworms that can infect humans to planarians capable of regrowing their entire bodies should they be unlucky enough to get chopped in half. The skilled swimmer in this clip belongs to the genus Pseudobiceros. Like other marine flatworms, it can propel itself through the water by undulating the edges of its body in a wave-like motion. 

Although they lack a respiratory or circulatory system, flatworms do have a digestive tract of sorts. Larger species have a branch-like gut that allows nutrients to be dispersed throughout their bodies. Most species lack an anus, so excreting undigested food is done through the mouth (unless you're a long flatworm, in which case you may be gifted with multiple anuses).

Most flatworms are hermaphroditic, meaning each individual possesses functional reproductive organs of both sexes. Which brings us to penis fencing. For some species of flatworm, mating involves a strange wrestling match. The flatworms rear up with their two-headed, dagger-like penises exposed and attempt to forcefully pierce each other's epidermis in order to inject sperm. 

Motherhood is physically demanding, so the goal for flatworms is to live the bachelor life for as long as possible. The worm that gets stabbed in these bouts of penis fencing will go on to produce young, while the victor can continue to do male flatworm stuff (we're guessing all-night reef parties). In some cases, both individuals will be injected with sperm. And then there are those species that do away with a mate altogether and simply reproduce asexually. 

Still, they look pretty when they swim right?

Header image: Jens Petersen

Octopuses are able to carry out these impressive feats of shapeshifting thanks for a very squishy, boneless body. Aside from their beaks, octopuses have no solid body parts. This allows them to contort their bodies in a magnificent fashion – if the beak fits, the rest probably will too. And if that’s not impressive enough, each sucker on an octopus's arm is loaded with as many as 10,000 neurons allowing it to taste and feel independently with each appendage. Even a surgically removed octopus arm can perform basic motions like grasping and reaching.

Arnold was eventually defeated by a 0.7” (1.7cm) wide gap, but he was still able to figure out a way to get at the treats. He put on a show of octo-strength, and brute force proved effective in removing the barrier. Good on ya, Arnold.

The undulating jelly was spotted more than 2,500 feet (762 metres) below the central Pacific Ocean by researchers working for the Ocean Exploration Trust. The team initially compared the animal to a ghost character from the classic 80s arcade game Pacman, but the jelly soon proved that it was far more versatile than that.

The deep-sea creature quickly began morphing into a formless blob revealing a small, red isopod hitchhiking beneath its sheet-like folds. The isopod, a type of segmented crustacean related to deep-sea pillbugs, is probably not being preyed on, but "it is likely that this small crustacean consumes pieces of jelly while remaining hidden from predators," the Ocean Exploration Trust explains in a blog post, adding that the relationship between the two is not yet fully understood.

The jellyfish belongs to the genus Deepstaria and is a relative of the even stranger D. enigmatica, a species only seen a handful of times. Unlike other jellyfish, these ghostly creatures do not have stinging tentacles, so scientists are not entirely sure how Deepstaria eat. It's thought that they are filter feeders, trapping prey inside their expansive bag-like bell. A geometric mesh pattern serves as a network of canals along which food can travel to the stomach at the top of the bell. "As the jelly can reach a large size when inflated, these channels help distribute nutrients across the entire expanse," the team explain online.

The Nautilus research vessel is currently exploring the Pacific Remote Islands Marine National Monument, an expansive marine protected area spanning 490,343 square miles (1,269,979 square kilometres) in the central Pacific Ocean. The team are collecting deepwater baseline information to support science and management decisions in the area. For more updates from the almost-always fascinating ocean depths, visit the Nautilus website.

The disguise was so effective, in fact, that it took the experienced diver several seconds to figure out what he was looking at. 

"When I turned my video light on to video the motion of a jellyfish, it began to shake and turn," King told Caters News. "The jellyfish emerged from the bottom and started 'running', as witnessed in the video. It was alive and well but attached tightly to a carry crab."

As their nickname suggests, "carry crabs" (a colloquialism used to describe many members of the family Dorippidae) use modified hind legs to grip any items that might make for good cover. The strategy yields incredibly effective camouflage – like the marine equivalent of a ghillie suit.

Claims that this crab is exploiting the jelly's "stinging tentacles" for protection, however, are not entirely accurate. The billowing lobes you see in the clip aren't tentacles; they're "oral arms" – frilled masses of spongey tissue used for filter-feeding. 

And while it might look like the crab in the footage is holding its hostage in an abnormal position, this jelly actually prefers things to be topsy-turvy. 

Upside-down jellyfish (genus Cassiopeia) like the one in King's video spend their days planted on the seafloor, where they rest on their bells and feed on tasty plankton. Filter-feeding can be done right-side up, but there's a good reason behind the jelly's contrary orientation – and it's hidden within the oral arms. Much like corals, Cassiopeia jellies harbour symbiotic algae within their tissues. In exchange for free room and board, the algae provide their jellyfish hosts with extra nutrients – as long as they get enough sunlight to photosynthesise. Inverted living, then, ensures the jellies' tiny tenants get exactly what they need.

Spot the crab! Here, a decorator crab hides in plain sight under Cassiopeia cover!

Upside-down jellies tend to congregate in large groups (like the one in the header image of this article) and stay put, so it's likely that the crab simply plucked one for the taking. 

Of course, crabs cart around more than just jellyfish! Banana peels, tissue boxes and other invertebrates are among the mobile disguises used by crafty crustaceans. Back in 2016, Earth Touch contributor Mark Thorpe managed to film this one – and its "star-butt" urchin veil – in Indonesia's Lembeh Strait:

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Top header image: Adam Fagen/Flickr

Meteorologists with the National Weather Service (NWS) first noticed the sizeable mass on their Doppler radar earlier this month, but misidentified it as a flock of birds. In the hopes of finding out which species of feathered friends they might have encountered, the NWS team posted a video of the discovery on social media. It didn't take long, however, for ornithologists to chime in and poke a hole in the hypothesis: the cloud was moving in the wrong direction.

Winter has already begun to take its icy toll on Colorado, sending local birds southwards in search of warmer weather. The cloud on the radar was headed north. An alternative explanation came when Denver residents began reporting that thousands of painted lady butterflies (from the subgenus Cynthia) had suddenly descended on their gardens and homes.

Could it be butterflies? Butterflies EVERYWHERE in #Denver !

— Brett Perry (@brettperry_) October 4, 2017

Tiny animals like butterflies rarely produce radar signatures of this clarity and magnitude, but when enough insects link up, it's possible for them to be confused for something much larger.

"Things with big wings need to fly together in the same direction with the wind to generate that signature," NWS wrote on Facebook. "Migrating butterflies in high quantities explains it!"

The butterflies appear to have taken off in El Paso, Elbert, and Douglas counties before finally forming an impressive kaleidoscope that drifted across Denver. It's hard to say what prompted the rapid jump from city to city, but the day after NWS detected the high-activity signature, the winged travellers who caused it appeared to be laying low, spending their time gulping down nectar.

Butterfly numbers tend to increase when flowers are plentiful, so it's possible that recent weather changes sent the population towards more promising food sources. NWS meteorologists suspect cold snaps in the area may have had something to do with the rapid migration picked up by their instruments.  

"We cannot recall seeing this radar signature in our area before," the team said. "There was something unique about Tuesday ... apparently the butterflies felt compelled to migrate northwest."

Some butterflies actually "surf" wind currents to save energy during their lengthy journeys, so it's also possible that the shift towards Denver was incidental – the butterflies may have simply been blown off course. That might explain why even people living on Colorado's snow-dusted mountain ranges reported hundreds of butterflies around their alpine homes during the event.

"I couldn’t believe my eyes," local resident Susan Schinner wrote on Facebook in response to the NWS video. "We live at 10,000 ft. and we have about four inches of snow on the ground. When I took the dogs for a walk, there were butterflies everywhere!"

In any case, these animals aren't likely to continue on a northerly trajectory. Colorado-based lepidopterist Sarah Garrett explains that painted ladies tend to move towards warmer habitat in places like Arizona, New Mexico, and even the upper reaches of Mexico as temperatures drop. In fact, last month a different painted lady population crossed through Colorado's Front Range on their way further south.

"I have been getting phone calls from people all over the Front Range in many different counties,” Garrett told The Denver Post at the time. "Last week, I spoke to folks in North Dakota and South Dakota who have seen them. They are making their way progressively through these Western states."

Where will the orange visitors head next? Help scientists find out out by reporting your sightings!

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Top header image: coloneljohnbritt/Flickr

Underwater photographer Connor Gallagher filmed this encounter with a juvenile sunfish (Mola mola) just recently near Monterey Harbor, where he took a swim through the jellyfish horde in a protective full-body wetsuit:

A post shared by Connor Gallagher (@connorgallagherproductions) on Jul 7, 2017 at 1:44pm PDT

"I had an inkling to hop in for a snorkel after my run when I saw a few [jellies] in the shallows," Gallagher wrote on Instagram. "Tens of thousands of these guys showed up while I was in the water filming a few hundred."

We haven't seen a gathering like this one in a number of years, but the jellyfish "minefield" is no reason to panic (and it's not a sign of a permanent jellyfish takeover, either). Under the right conditions, surface winds circulate cool, nutrient-rich water up from the deep ocean. With it comes tasty plankton, creating the perfect environment for a bloom of this size to thrive. This year's upwelling has been particularly significant, and recent heavy winds gave the jellies – commonly known as sea nettles (Chrysaora fuscescens) – a boost towards shore. 

According to Monterey Bay Aquarium staff diver Patrick Webster, so many sea nettles arrived in the bay this week that they clogged the aquarium's intake pipes. "It just looks like nature's lava lamp where you have millions of animals that are bright orange and floating around," he told SF Gate.

Gallagher did wonder whether the sunfish he encountered had became disoriented after receiving numerous stings from the jellies: you can see it shaking off one of its tentacled assailants in the clip.

Sea-nettle stings aren't deadly, but they do produce a painful "electric throbbing" sensation in humans. Sunfish skin, however, is extremely rough, and this animal doesn't look too out of sorts. The same can't be said for the human in this encounter: despite his best protective efforts, Gallagher did take a few hits from the jellies. "It paid off, except for the stings to my shnoz," he said. 

Ocean sunfish are known for their gargantuan size (not to mention the ability to send Bostonions into a panic, "bro"), and while the largest specimens spend most of their time offshore (just look at the giant below), juveniles are regularly seen in Monterey Bay. Interestingly, more impressively sized sunfish tend to return to the shallows when they aren't feeding, and scientists suspect that vertical migration helps the animals warm their large bodies. 

These gentle giants regularly feed on jellyfish and other invertebrates. Beyond a mola's comically small mouth, the path to the stomach is lined with a slimy, viscous tissue that's believed to counter the stinging effects of ingested tentacles.

Sunfish use their beak-like tooth plates to shred slippery prey, which is sucked through the mouth repeatedly to break it apart. Here's one slurping down (harmless) by-the-wind sailors in nearby Point Lobos:

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Top header image: Nano Maus/Flickr

The clip has been shared over 400,000 times since the Invertebrate Studies Institute posted it to its Facebook page, but the original was actually shot by Pakistan resident Shuja Jan back in 2012. Jan spotted the lizard-rolling beetle in Nushki, a small town in the country's Balochistan province. 

We've reached out to several dung beetle specialists (yes, that's a thing!) to find out more about the beetle's odd "ball", but while we await more information, let's break down what we do know.

Dung beetles fall mostly into two groups: the subfamilies Scarabaeinae and Aphodiinae. There are over 5,000 known species (and counting!) in Scarabaeinae alone, and we're only just starting to figure out how many of them reside in the area where this footage was filmed. However, a 2014 review and survey found that one "particularly massive" species, the black beetle Catharsius platypus sharp, had set up shop in Balochistan.

That doesn't necessarily make this the ID for our reptile-rolling friend, but it's possible that the beetle in Jan's video is at least a relative. 

While some online commenters jokingly suggested the lizard had simply enjoyed one too many sips from the local cacti, the reptile is undoubtedly dead. That said, the exact circumstances surrounding the beetle's "haul" are a bit unclear. 

Dung beetles prefer to dine on a diet of herbivore excrement, but at a pinch, they'll pick up whatever form of faeces they can find. Some species, like Coprophanaeus lancifer, do bury carcasses from time to time. It seems somewhat unlikely* that the beetle planned to eat the large lizard, but its body may have provided a suitable depository for dung beetle eggs. (Nothing says "welcome to the world" quite like raising the kids in a bed of rotting flesh.)

We'll be updating this article as we get expert feedback, but if you've seen this behaviour before, we want to hear from you! 

Want to learn more about dung beetles? Here's more than you ever wanted to know.

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* UPDATE (JUNE 11, 2017):

Lund University associate professor Dr Emily Baird, who has done extensive work with dung beetles, told us that this individual would have fed on its supersize spoils, much to our surprise.

"What an amazing video!" she said. "The beetle will most likely dig a large hole and bury the lizard underground where it will stay and eat it until it is gone (this would take maybe a week or so)."

If egg-laying had been the plan, we would have seen a pair of beetles working together to move the carcass, she explained. 

"As there was no other beetle, it is very unlikely that eggs would be laid so it is more likely just a good source of food! I have seen a beetle burying a snake once in order to eat it but the snake was too big for the beetle to move so the beetle just dug a hole under the body."

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Top header image: Jochen Smolka/Flickr

A video of what looks like a possessed pancake has racked up nearly 600,000 views since it was posted to Facebook recently by Oregon fly-fishing guide Kate Taylor. What you're looking at is a Pacific razor clam, a bivalve mollusc in the genus Siliqua.

These meaty shellfish inhabit sandy, surf-swept beaches from the Aleutian Islands south to California – and if you've spent time meandering along North America's Pacific coast, you've probably walked right over one. Razor clams typically go unnoticed by human passersby because they're master diggers. 

The clams are filter-feeders and spend their days slurping tasty plankton out of the surrounding water. But unlike the clams we're used to seeing, their shells cannot close tightly. To avoid drying out between waves, the animals must sink about a foot (30 cm) into the wet sand. You can see this in action in Taylor's video.

That wriggling noodle on the right side of the clam is the muscular foot, a structure that both pushes sand out of the way and acts as an anchor to pull the animal to the desired destination. On the other end is one of the siphons, tube-like straws that move water over the gills ... which brings us to the momentous eruption at the end of the clip. While many commenters online have suggested the clam is expelling the remnants of a large meal, that brown eruption is a combination of water and sand. 

Retracting the siphon forces water up and out, which results in that signature squirt:

When water is removed during a squirt, more rushes in to take its place. This flow of water creates a quicksand effect that reduces drag on the shell and makes for a quicker escape!

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Top header image: minustide/Flickr

When spiders need to get out of dodge fast – say, during a flood – many of them will use a tactic known as "ballooning". By shooting a silky strand skyward, the spiders can sail to safety on the back of the wind. Exactly where they land depends on which direction the breeze takes them, and occasionally they arrive en masse. 

"There were heaps of little spiders landing on the car, in the car, everywhere – it was like something out of Harry Potter," Tauranga resident Kirsten Green told The New Zealand Herald.

While the resulting giant cobweb might look a little creepy, it's nothing to be concerned about, nor is it a sign of a spider population boom. This is the same phenomenon that turned Wagga Wagga in Australia into a "ghost town" back in 2012:

It also brought "black raindrops" to Brazil the following year:

This reverse-parachuting also helps spiders colonise new territory, but it can be a risky manoeuvre. Many of the individuals that take to the skies will be eaten by birds or killed by rough weather, for example.

Experts urge anyone who encounters a ballooning event to remember that these animals are beneficial to ecosystems, and not inherently dangerous to people. 

"There's no need to disturb the web," added Canterbury Museum curator and spider expert Dr Cor Vink. "It's not there to catch anything. It's just spiders, wandering around."

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Top header image: castgen/Flickr

Scientists with the Monterey Bay Research Institute (MBARI) and GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany spotted the seven-armed octopus during a recent dive off California's coast. Amazed by the sighting, the team watched on as H. atlanticus began to eat the egg yolk jellyfish (Phacellophora camtschatica) clutched between its arms. 

Tucking into a gelatinous meal is the norm for many creatures: sea turtles, Mola mola and other large fish all have a fondness for gooey prey. But scientists had assumed that in the deep sea, where food is scarce, jellyfish meals weren't nutritious enough to warrant the effort it takes to find them. 

MBARI team member Steve Haddock suspects that while jellies might be lacking in nutritive benefits, they do make up for it in abundance and mass. In other words, they're less a high-calorie hamburger and more an all-you-can-eat salad bar.

What's more, the Haliphron octopus seemed to target the digestive tract of the jellyfish, which would allow it to gain access to any nutrients in the food the jelly itself had eaten.

To make sure the sighting wasn't an anomaly, the team looked into the bellies of five dead octopus specimens, and all of them contained at least traces of gelatinous prey. Three contained jellyfish, while the others held a salp and siphonophore (a colonial jellyfish doppleganger), respectively.

"Haddock feels the general sentiment surrounding gelatinous diets in oceanic food webs has been unappreciated and underestimated," says MBARI. 

Want more seven-armed action? H. atlanticus was also seen last year when it cruised past an underwater camera in the Philippines! Learn more about the species here.

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Top header image: John Kroll/Flickr

When it comes to a duel to the death between a hungry red octopus and a crab, the smart money's on the octopus, even if the crab in question turns out to be remarkably nimble. After all, the octopus is one of the most intelligent invertebrates in the world, and in this case twice the size of the crab. Despite the crustacean's valiant defence, it seems only a matter of time before it's crushed by the beak of its eight-armed foe.

Then, the unexpected happens.

The battle unfolded in California's Monterey Bay, where divers Patrick Webster and Connor Gallagher caught it on film. And yes, they were as surprised by the harbour seal's game-changing cameo as we were.

"A showdown between predator and prey, locked in a deadly dance," Webster wrote on Instagram. "You'll never believe what happens next!" Considering we fully expected to watch a defiant crab turned into a cephalopod snack – that is usually what happens, barring a seal ambush – he's certainly right about that.

The crab's pinniped saviour is actually a known entity in the area, according to Webster, who works for the Monterey Bay Aquarium. Affectionately nicknamed "Whiskers" by local divers, the seal has learned to take advantage of the illumination provided by dive lights when searching for prey. Fortunately, both divers were armed with cameras, so they were able to catch the dramatic intervention from multiple angles.

"We saw him earlier in the dive, but by the time Connor found the octopus, we hadn't seen him in a while and figured he left to go hunt elsewhere," Webster told GrindTV. "He was entirely out of my mind when he swooped in and ate the octopus, so I was completely surprised."

We also have to tip our hats to the duo for the wrestling match audio. Points for extra dramatic tension.

A post shared by Patrick's Pretty Pictures (@underwaterpat) on Feb 10, 2017 at 9:01pm PST

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Top image: Jerry Kirkhart/Wikimedia Commons

YouTuber and underwater videographer PT Hirschfield encountered what has been nicknamed the "balloon" octopus while diving off the coast of Melbourne, Australia. The animal had been hunting crustaceans when Hirschfield made her way towards it – to be greeted with the peculiar display you see above.

"This octopus was not impressed when I interrupted its morning feeding stroll," she recalls on YouTube. "It blew itself up like a parachute multiple times to try to intimidate me, before trying to torpedo me like a bowling ball!"

It's possible that the Sydney octopus (Octopus tetricus) was trying scare off the human interloper – many animals, like pufferfish, employ the "make yourself big" manoeuvre to get out of dodge. But scientists have put forward other explanations since the video was posted.

In an interview with LiveScience, Dr Kathleen Sullivan Sealey, an associate professor of biology at the University of Miami, suggests the octopus was merely continuing its foraging mission. By spreading its arms like a large net, it might be trying to trap potential prey near its crushing beak.

What's more, by channelling water through its mantle (the bulbous structure above the eyes), it could be forcing shrimp and other small invertebrates out from under nearby rocks – essentially using its body like a power washer. 

Dr Crissy Huffard of the Monterey Bay Aquarium Research Institute (MBARI) agrees. "Many shallow-water octopuses do a version of this. They 'cast' their web over rocks or seaweed and catch the prey that gets trapped underneath." Similar foraging behaviour has been observed in other octopus species, too.

Hirschfield suspects it may have been a combination of the two – feeding and posturing – but it's also possible that this was something else entirely. 

"Towards the end of ten minutes it definitely seemed to want its own space, and made no apologies for hunting for crabs right next to my body in a way that I'll admit was a bit intimidating!" she told LiveScience. "[It] decided to send me a strong message by torpedoing directly at me like a bowling ball with tentacles. I got the hint and let it go."

We'll post updates if more information about this behaviour comes to light. If you've encountered something similar on a dive, let us know in the comments below!

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Top header image: John Turnbull/Flickr

Incubating inside this mirrored palace is Mechanitis polymnia, the orange-spotted tiger clearwing. And while it might seem that such flashy dwellings would leave this animal prone to predation, the opposite is true. 

Butterfly pupae are easy targets: defenceless protein sausages that are too busy scrambling and rearranging their insides to fend off would-be predators. It forces them to conceal their identities in order to survive this dangerous life stage – and polymnia relies on light-bending to do the trick.

"They are actually very hard to see in nature, given the way all the colours are reflected," explains Dr Keith Willmott, one of the world's leading tropical butterfly experts.

The tactic works a charm, and is actually shared by species in several other groups, like milkweed butterflies (genus Danaidae) and those in the genus Tithorea.

Contrary to some comments online, these structures don't contain metal particles; they're made of chitin, the same substance that gives insects like jewel beetles their shine and turns the sea mouse into a rainbow-coloured, fibre-optic lamp. 

But that's not the only fallacy about these animals floating around the web. A quick Google search will tell you that the empty chrysalises were once used as currency. It's tempting to conjure up the scenario: baskets filled to the brim with sparkling caterpillar cases and ancient peoples combing the undergrowth for the rainforest's doubloons. We humans certainly love our shiny things, but after speaking with half a dozen butterfly specialists, it looks like there's no truth to this historical nugget.

For starters, empty (or "dead") pupae are extremely fragile, so the idea that they would hold up long enough for currency exchange is farfetched. And there's another problem, too.

"The butterflies are only in the pupal stage for around a week, depending on the species," explains Dr Ryan Hill, who reared Mechanitis butterflies for his research in Ecuador. "Afterward, they lose the metallic colour."

Costa Rica native Luis Ricardo Murillo-Hiller, who has been studying butterflies and working with butterfly farmers for 25 years, agrees. "They lose their metallic colour almost immediately," he says. "I have never seen or heard of somebody, in any place, using the pupae as currency, and actually, they are almost to unknown to [the average person]."

These pupae aren't very abundant, so unless you're out searching – and we mean really rooting around – in the local flora, chances are you'll never find one.

That's one myth busted – but our dig into internet lore did reveal that there is a lot we don't know about metallic camouflage. Some speculate that being shiny has other protective benefits too.

It's possible that the reflective properties of their chrysalises mask the butterfly larvae by making them look like something else entirely: hanging drops of water, shafts of light, empty pupae, or dry, curled leaves.

"The empty pupa idea is pretty cool," says Hill. "There are studies on seed colouration showing that when seeds are mottled they resemble empty seeds, and so are passed up by [seed-eating animals]. I would love to do a study on this in insects!" 

For hungry animals that get too close, the mirror effect might also be enough scare them off. Birds, lizards and other visual hunters like jumping spiders scour native plants for prey, and reflected movement (or the sudden appearance of their own reflected form) would likely initiate a bail sequence. 

These caterpillar contractors are among countless examples of the incredible biodiversity the rainforest has to offer. And yet over 750,000 square kilometres (289,000 square miles) of this vital habitat have been destroyed since the late 1970s.

Costa Rica has made encouraging strides to combat deforestation. In 1996 the country issued a complete ban on razing mature forest, and in the years since we’ve seen significant growth. Half of the remaining rainforest is now protected under national parks and biological reserves – but even here, just a quarter of the original tree cover is still standing and agricultural expansion continues to threaten what's left. If we want to unravel the rainforest’s many secrets, we should be doing much more to protect it.

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Top header image: Kristi/Flickr

To get into the holiday spirit, we've rounded up some of our favorite facts about these colourful creatures, starting with the obvious: what are those branches actually for? 

1. Tree sieve  

The Seuss-style plumes you see above – which come in an array of colour morphs – are called "crowns", and you'll notice they appear in pairs. That's because each worm has two of them. By pumping water up and over the crowns, a Christmas tree worm can filter out tiny plants and animals to snack on. The feathery structures are lined with both sticky mucus and spiky bristles (called cilia), which help trap passing prey.

2. Double duty

After a bit of size sifting, the worm moves any tasty morsels – conveyor-style – to the mouth, but the crowns do more than just catch food: they also harness oxygen! For this reason, the structures are often mistakenly called gills.

3. Now you see me

Underwater "pines" might be beautiful, but they're really just the tip of this worm's iceberg. Two-thirds of the body of a Spirobranchus lies hidden in a calcium carbonate tube, which it erects as a bunker. 

Some groups take this one step further, by setting up shop in stony corals. But the crafty worms don't do the heavy drilling: by nestling their bodies against the corals' living tissues, they force the polyps to build around them. Over time, these coral-encased bunkers can reach ten inches in length. 

Spirobranchus worms are pretty choosy about which corals they settle on, but scientists are still working out why. Some speculate that landing on carefully selected species could help the worms with reproduction. Others suggest the pickiness comes down to avoiding accidental predation (no worm wants a coral-munching parrot fish is hankering for its home turf).

4. Only the classics for these worms

Once settled down, a Christmas tree worm can live upwards of 30 years! (Though 10-20 is more common.)

5. Ladies and gents

While many invertebrates reproduce asexually, there are actually male and female Christmas tree worms. These animals are broadcast spawners, meaning they shoot their genetic contribution into the surrounding water, in the hope that it meets its match. Once fertilisation occurs, it takes just 24 hours for a larvae to develop. 

Meet Melibe viridis, a carnivorous sea slug with a gelatinous vacuum cleaner for a head. The fascinating sea-dweller was filmed by Emeric Benhalassa off the coast of Bali in 2016, and unsurprisingly, it generated a fair amount of interest (and confusion) online.

"I'm pretty sure that's a scrotum-headed nightmare sponge," one Reddit user proclaimed. The description is perhaps not that far off. Melibe viridis is equipped with a large, net-like mouth that it spreads out to snag its prey in an action similar to the plastic grabby-jaws of a Hungry Hungry Hippo (for some reason Hungry Hungry Nudibranchs never really took off).

The inner edge of the expandable hood is fringed with sensory papillae that help the nudi detect when a tiny crustacean has strayed into the death net. Most nudibranchs (and many other molluscs) are equipped with a rasped, tongue-like structure called a radula, which they use to cut and break down food before it enters the oesophagus. But members of the Melibe genus are not like other sea slugs, and their gooey head-nets set them apart from the crowd.

Other Melibe species, like the hooded sea slug (Melibe leonina), will attach themselves to blades of kelp and sweep their raised hoods downward or to the side. If an unfortunate planktonic creature settles on this translucent "fishing net", the two sides of the hood are slammed together like an underwater Venus flytrap, and tentacles ensure prey is locked in.

Similar to other nudibranchs, Melibe are hermaphrodites and fertilisation of eggs happens internally. Unlike other nudibranches, though, they smell a bit like fruit. In the case of the hooded sea slug, the fruity odour is most noticeable when the animals are removed from the water or when several individuals are grouped together. It's believed to be a kind of pheromone that the sea slugs use to communicate with each other. Nudibranch perfume, if you will. 

Melibe viridis can be found throughout the tropical Indo-West Pacific, with a small population hanging out in the Mediterranean. Although the jelly head may look a little unsettling, the species typically grows to a maximum length of just 130 mm (five inches), so your fingers and toes are probably safe. 

When bizarre photos of a fish "inside of a jelly belly" surfaced this week, they quickly made the rounds online. But after checking in with some jellyfish biologists, we found that these strange snapshots might not be quite what they seem. 

It certainly looks like the fish was eaten by the jelly (and many media reports have suggested this is the case), but what you're looking at is more likely the end of the road for the fish's jellyfish abode, not for the fish itself. 

"When I saw it, I was filled with amazement and curiosity," says wildlife photographer Tim Samuel, who encountered the strange pair last December. "I had never seen anything like it. It was so strange and unusual, and it was really interesting to see how it would move through the water. The fish propelling the jellyfish, but wobbling around, and being thrown off course." 

Samuel's description makes sense – and that's because we're looking at what is probably not a living jelly, but rather a segment of the animal's bell that has folded in on itself, the aftermath of the jelly being eaten by a sea turtle or some other predator.

Jellies don't shed pieces of their bells on their own, and the structure still appears in good condition. This suggests that the jelly probably met its end not long before Samuel came across his strange find.  

"As a surfer I've always had a love for the ocean," he says. "Taking photos of wildlife allows me to combine two of my favourite things: photography and the sea. My goals as a photographer are to generate a conversation and inspire people with all the beauty the ocean has to offer. I'm happy my photo has achieved this." 

Speaking with Australian Geographic, University of Queensland ichthyologist Ian Tibbetts identified the fish as a juvenile trevally, one of a number of fish species known to take refuge under the bells of passing jellyfish. It's a behaviour we've seen before in the juvenile shrimp scad:

It's possible that the trevally simply attempted to hide – invisibility cloak-style – inside the bell fragment, and became trapped when the membrane wrapped around it. 

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Top header image: Daniel Slaughter, Flickr

A lengthy stint in the Amazon often means getting wet, muddy and stung – but for scientists hoping to unveil the secrets of the most elusive rainforest inhabitants, it's a venture well worth the trouble. That's how entomologist Phil Torres first made the butterfly-ant discovery near Peru's Tambopata Research Center.

While hiking on a nearby trail, Torres spotted an adult metalmark butterfly (Adelotypa annulifera) drinking nectar from the tips of bamboo shoots. There was nothing unusual about the scene – until he noticed something else. The ants that call the shoots home, and rely on their sweet secretions for survival, were doing nothing to defend their territory from the butterfly interloper. 

After snapping a quick photograph, Torres moved along, but curiosity came calling and he returned to the site for a second look the following morning. "The next day, that one butterfly turned into three butterflies all doing the same thing and I thought, OK, this is going to be something cool," recalls Torres. 

Determined to find out just what was going on, he tagged in biologist and colleague Aaron Pomerantz, who would be spending time in the area later that year. "I was really mind-blown when I first saw the pictures," says Pomerantz. "Despite years of being involved in entomology, I had never heard or seen anything like this before.

While ants might not seem like particularly threatening adversaries, some species in the Peruvian Amazon – like the infamous bullet ant – can inflict an intense, venom-packed sting. The experience has been likened to walking over flaming charcoal with a three-inch nail embedded in your heel. And that's the level of pain the ants can inflict on adult humans. For tinier recipients, a sting could certainly do damage. 

"How does this butterfly not get torn to shreds by the ants?" Pomerantz wondered.

Lifetime liaisons 

Several months later, Pomerantz  visited the site in the hope of witnessing similar behaviour from the adult metalmark butterflies – but he found something more.

Hidden beneath a dead leaf on the tip of one of the bamboo stalks were dozens of metalmark larvae – and the ants were tending to them like a horde of willing wet nurses. Combined with Torres's previous observations, this led the scientists to suspect that the butterflies interacted with ants throughout their entire life history: from egg to egg-laying adult. 

The million-dollar question: what's in it for the ants? In the early stages of life, butterfly larvae are basically defenceless protein sausages, and would make a fine meal. But even the ornery bullet ants showed no interest in a buffet-style binge. Torres and Pomerantz explain that the caterpillars' saving grace comes in the form of a nutritious goo they secrete, which the ants can feed on. 

The substance, expelled from a specially evolved "nectary" organ, is rich in both sugar and amino acids. And because bamboo is not a particularly good source of energy, it's possible that the caterpillars' offerings surpass that of the host plant.

Food for defence is a trade-off we've long observed in the natural world, and in fact, some species take it one step further. The secretions of the Lycaenid butterfly caterpillar, for example, have powers of mind control. Chemicals within the goo interfere with dopamine production in the ants that eat it, turning them into armoured rage-heads. 

The caterpillar-ant interaction Torres and Pomerantz observed in Peru appears to be mutual – but that doesn't explain how the adult butterflies manage to stay in the ants' good graces. The team even observed a butterfly stealing a droplet of nectar straight from the mandibles of an ant, the first time this has been documented.

"This is most likely achieved by some sort of pheromone signal," explains Pomerantz. "Ants aren't very visual, but they communicate primarily through chemicals. Somehow the adult butterfly may have evolved the right chemistry to 'trick' the ants into not attacking them, perhaps by mimicking the ants' own chemical signature or by recycling the chemistry from its larval stage that says 'hey I produce good stuff, don't eat me'."

At this point, it's anyone's guess, but the scientists are hungry (no pun intended) to get back in the field to discover the method behind the metalmark's madness.

A dirty affair

While spending weeks or even months beneath the lush canopies of the rainforest sounds like a great adventure, discoveries like this one often involve a lot of pretty monotonous grunt work. We're talking waiting for hours for a single butterfly to move from one leaf to another. 

"The most memorable waiting period for me was when I had to watch the butterflies' butts to see what happens when they pee," recalls Torres. 

Because the ants would occasionally tap their antennae on the butterflies' backsides, Torres was convinced that – if he waited long enough – he would see whether the adult butterflies were offering the ants some nutritious liquid, like their caterpillars.

"But after hours of waiting and witnessing three 'urination events', I concluded that the butterflies would just pee whenever they wanted, and the ants wouldn’t respond to it whatsoever. I went a little crazy being eaten up by mosquitoes and sitting cramped staring at butterfly butts. I took a selfie to remember it by."

Puzzles abound 

The rainforests surrounding Peru's Tambopata Research Center are some of the most remote and pristine in the world, holding the promise of many a future discovery. Yet this wilderness, along with the rest of Amazon, is at risk of vanishing before we can uncover its secrets. 

Since 1978, over 750,000 square kilometres (289,000 square miles) of rainforest have been destroyed across Brazil, Peru, Colombia, Bolivia, Venezuela, Suriname, Guyana and French Guiana. More than three-quarters of that cleared land is now devoted to cattle ranching. 

As humans continue to expand their reach, roads have also been opening up previously inaccessible swathes of land to illegal logging and poachers.

All of this makes protected areas like the vast Tambopata reserve increasingly precious. The region's old-growth lowland forests have existed mostly untouched by human activity for some 30 to 50 million years. 

Beyond life in the undergrowth, the park shelters over 170 species of mammals, 670 birds and some 20,000 different plants – and that's just what we've found so far. For conservationists like Torres and Pomerantz, it's vital that this haven remains protected.

The team will return to the jungle in the coming years to delve deeper into their discovery – and there are many questions still waiting for answers.

Are interactions between butterflies and ants more common than we thought, and simply overlooked because the rainforest is so big, and these critters so small? Do the butterflies' red spots mimic the appearance of the dangerous ants they rely on, making them less appealing to predators? And just what kind of chemical trickery is used to fool the ants? 

"This butterfly-ant relationship was a puzzle that literally kept me up at night," says Torres. "I would browse through the images telling myself I must be missing something. And eventually, I found those missing somethings. Photography helps pause your natural history observations and allows you to really soak in what nature shows you."

For stunning images of wildlife and updates on their adventures, keep up with both Torres and Pomerantz on Instagram, and the Jungle Diaries YouTube channel. The A. annulifera life history paper can be found here. 

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Top header image: Phil Torres

Yet every once in a while, a pyrosome shows itself to the world.

This strange, red windsock was spotted off the coast of Akumal, Mexico. It is very much alive, and made up of thousands and thousands of tiny clones.

The crew of Expedition Akumal came across the colony while working to remove invasive lionfish from the local reefs. With over 20,000 dives logged between them, not a single member of the team had ever seen a pyrosome. In fact, they initially mistook the Borg-like creature for trash.  

"It was drifting and hovering in an odd way at about 80ft of depth," recalls diver Ivan Perez. "We remove any plastic we find so that turtles will not mistake it for jellyfish and try to eat it." 

As the team approached the drifting structure, its true nature was revealed: the tube was not man-made, but rather a colony of tiny organisms called zooids. 

"As we watched, it became more mesmerising!" says Perez. "It was open at one end with nothing inside and yet it seemed to move as if the tapered end was some kind of head. There were no eyes or anything like a face. It was entirely made up of tiny, clear elongated bubbles. Each had a spot of red in it. These tiny creatures made up a whole."

The zooids that make up one long pyrosome are clones of one another, with each individual capable of adding to the colony by copying itself. They manoeuvre around using a suck-and-blow strategy akin to jet propulsion, working together as one singular organism to pull and push water through tiny slits in their bodies. 

"And like members of the Borg, which are mentally connected, pyrosome members are physically connected– actually sharing tissues," adds marine bioligst Dr Rebecca Helm. 

A pyrosome's shape is held by a gelatinous "mucus baloon", which suspends each zooid within its walls. The individual mouthparts are aimed away from the balloon's hollow interior, continuously taking in water as they move fluidly through the ocean. Nutrients are filtered out, and any waste is passed on into the empty space in the middle, where it flows out into the sea.

And as we all know, many hands make light work. A zooid may be just a millimetre long, but reports exist of animals as large as penguins getting trapped within the tube's interior. They might be feathery and delicate as individuals, but a pyrosome colony produces a relatively strong current. 

The colonies are often confused with squid egg masses because they're similar in appearance – in fact, we actually made that mistake ourselves when this one popped up on YouTube:

It's an easy mix-up, but Smithsonian Museum of Natural History squid expert Dr Michael Vecchione confirms the Akumal sighting is definitely a large pyrosome. 

The specimen is impressive, but these animals can get much, much bigger. Pyrosomes are known to reach lengths of 60 feet (18.2 metres) in length – that's longer than most whales! 

Though they're rarely seen by divers, these animals aren't exactly inconspicuous, so what's to stop marine predators from feasting on the largely defenceless colony? The clue is in the name, which comes from the Greek "pyro" (meaning "fire") and "soma" (meaning "body").

"Pyrosomes are known to produce one of the most spectacular bioluminescent displays of any animal," explains Dave Bennet, one of the only marine biologists to actively study these animals in recent years.

As with many deep-sea inhabitants, it's thought the bioluminescence here acts as a warning, a smoke-and-mirror display to ward off would-be predators.

"Your prey suddenly glowing blindingly all around you is enough to scare most away," explains Bennet, adding that there is still a lot to learn about these little-studied organisms. For example, we still don't know just how their light organs actually work. 

"Every time I tell another biologist what I’m studying they inevitably say ‘What? What’re they?'," he says. 

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Top header image: Nick Hobgood/Flickr