8 Strange sea creatures you likely didn’t know exist

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Our planets waters are full of strange creatures. The deeper the water and the saltier it is, the more likely it seems that we find strange animals out there. So let me take you on a roll for some creative inspiration in a world that's still full of surprises and will keep on surprising us for much, much longer!

Hi! My name is Tessa, I’m a Dutch artist, art director, and creative project manager. I love to share my passion for this craft, nature, art and fantasy, and do that by creating this archive and community, alongside my company Tez Art & Design.

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Strange sea creatures

Strange sea creatures are found throughout the world, and many new ones are discovered every year again. You can find top (fill in number) of strange sea creatures everywhere, containing animals like the gulper eel, dragon fish, and angler fish. I did my best though to come up with species I didn’t see in these lists. I hope you enjoy, and let me know which ones you didn’t know of yet!

Phylliroe atlantica, the slug that looks and swims like a fish

As cute as the name is, as beautiful is the slug. This beautifully translucent sea slug looks like a fish, hunts like a fish and moves like a fish. It’s a nudibranch family the size of a goldfish and related to sea bunnies, yes, they are a thing too! The long horns aiming sideways are called rhinophores. With these rhinophores it manages to sniff out its primary prey: Jellyfish.

Unlike nearly all slugs, this slug mostly lost its foot. This is the part of the body where any other slug moves around with. The Phylliroe sacrificed most of the foot for life in the open sea. But part of the foot is still there and crucial for its survival. No, it’s not for latching onto a surface to stay grounded, it’s located near the mouth and is solely used to to hold onto the jellyfish that will be devoured by the translucent slug, after which its defecated out of the slugs body from the anus in the middle of its right side. Because, why not.

Like that’s not enough, the Phylliroe is one of the few slugs that’s also bio-luminescent. It’s able to switch their lights on and off! So we have a translucent glowing slug. This slug evolved to look, hunt and behave like a fish, and it has a ‘foot’ that latches onto its prey, hmm. Not to mention what the small offspring does to their food source: They latch onto a jellyfish and stay there. They will parasite this jellyfish and eat it alive until the jellyfish is either dead, or the Phylliroe outgrows it, devours whats left and moves on to its next target. Give me more of these pretty freaks of nature please!

How come it evolved the way it did?

The reason why this slug evolved the way it did is not entirely clear. Natural selection is the logical explanation. From what I know of evolution, I think it’s very likely that at some point a mutation took place which made the predecessor of this slug better at hunting and finding mates. In this case, speed was most likely the culprit. This mutated slug would have been able to get away from predators more easily, find plenty of food, and roam greater distances to find mates, allowing for a lot of offspring with likely the same kind of mutation. Overtime these mutated slugs would have survived better than those that didn’t have this mutation. And as time and likely interbreeding with (distant) family members took place, the trait would continue taking hold and likely develop even further up to a point where it can now amaze us all.

Hot air balloons floating in the ocean, the duobrancium sparksae

Yea, it’s not like we know much about this creature yet. It was discovered in 2015, in a deep trench, so at the time of writing this article (2021) little studies have been done because it’s difficult to get where these animals are found. This creature that looks like a hot air balloon is actually a comb jelly. Duobrancium probably already gave away on the fact that it has two long ‘branches’, or tentacles. It’s found in the waters of Puerto Rico. Even better: It’s mostly translucent and bio-luminescent, making it look even more like a hot air balloon. The jellyfish is roughly 6 cm (2,3 inch) long and the tentacles 30-56 cm (11.8-22 inch) long.

Remarkably, this species seems to move while keeping its tentacles on the sea floor, dragging the tentacles after its bell like a hot air balloon would do right before liftoff when the wind pics up. But it’s also possible that it’s actually attached to the sea floor, holding onto it, or simply got stuck. This comb jelly was first seen by NOAA fisheries using a ROV in 2015. But hadn’t been identified until 2020. It’s now thought its a completely new and/or unknown comb jelly species.

When a giant string turns out to be thousands of animals, the Siphonophore Apolemia

The first time I saw this ‘thing’ show up on the internet I thought it was a hoax. How can a huge string be an animal? I saw no heads or tails, it was just a string. But its no hoax, this creature is a colony of thousands of syphonophores. These syphonophores are deep sea predators related to jellyfish and corals. This species can only survive as a colony and they do so by cloning and staying attached onto each other and that way, merging into one big organism. Some of the parts are specialized to hunt, while others specialize to digest and move nutrients throughout the colony.
Like these creatures are not remarkable enough: They also hunt by creating a spiraling galaxy formation, covering a large area like a spiderweb, like seen below.

It’s very likely that this is the longest creature ever recorded on this planet, roughly 47 meter long (154 ft). And it’s probable that its decades, or even centuries old.

Elvis is back, and he’s feisty!

Anyone would be honored when a worm was to be named after you, right? I’m sure that if Elvis were still to be alive, he would be too. And guess what? Elvis has a family! Oke, but to be scientifically correct: The ‘Feisty Elvis Worms’ are actually a nickname for a scale worm species called Peinaleopolynoe. They come in many shapes and colors, but just for inspirational purposes, and the convenience of a video giving you a more than decent idea of these strange worms, we stay with the mineoi, orphanae, goffrediae and elvisi. The last one is named after Elvis Presley because the colors of this worm match that of Elvis’ signature suit.

These scaly worms are found in places that requires enormous adaptions, which makes them extremophiles. They live near hydrothermal vents, methane seeps, chemosynthetic-based ecosystems (with high levels of carbon dioxide or methane) and so-called whale falls, which is an area around the body of a dead whale.
These creatures have specialized to survive low oxygen levels by having elaborate gills under their scales.

These worms are 1 to 3 mm large and they live from sandy sediments that dry up during low tides to deep sea vents. The bristles to the sides are called Chaeta and aid the worms in their movements. The thickened scales are iridescent, which makes them stunning to look at. If you wonder why they’re called feisty, just have a look at this video!

Ruby sea dragon

Family of the sea dragons, which are a group of sea horses, to keep things easy for you, the ruby sea dragon is just as remarkable as its family members, the leafy sea dragon and the common sea dragon. They live near the coast of Australia. They live in depths no human can safely dive to, so an ROV is needed to find and capture these strange animals.
Unlike other sea dragons, the red one is kinda well.. Naked. It has no leafy appendages that function as camouflage, and red is a very striking color for an animal that can easily fall prey to predatory animals. A remarkable but important detail though: Red colors don’t reach deep waters, so, even while it’s a striking red: It’s no problem as long as it stays in deep dark waters.

Ruby sea dragon. did you know this species exist?
Image by: Josefin Stiller, Nerida G. Wilson, Greg W. Rouse , website

They don’t come small either. 23,5 cm (9,3 inch) seems to be the standard, but few specimens have been found.
The Ruby sea dragon has a so-called prehensile tail. It can use this tail to hold onto and manipulate objects. Other sea dragons don’t have such a useful tail, but sea horses do.

Fun fact:
Did you know that sea horses and sea dragons are actually fish? And that sea dragons differ from sea horses because of the way they move? Sea dragons are more mobile horizontally orientated than sea horses are.

When aliën meets crustaceans

Epimeria loerzae
Image by Christian Ferrer

There are many crustaceans out there, but did you see the spiked crustacean before, also known as the Epimeria loerzae? Oke, I didn’t, but its appearance is lovely! It has a wonderful shape no matter the angle you look at, and wonderfully bright colors. There are 85+ known species in the Epimeriidae family, which this particular crustacean is part of.
Amphipods can be found from the coastline all the way down to 5,7 km (18,684 ft) depth, and I wish I could tell you more about this colorful one, but you’ll have to do with a global description of amphipods, as very little seems to be known about this particular one.

Amphipods are very versatile. They live from the coastline to great depths, in warm waters to very cold waters. They are not usually found in tropically warm waters though, but they can be found in very deep and cold tropical waters. Amphipods usually are slow moving, but can be really quick when they need to run from a predator or are on the hunt. They can only do this for short bursts though.

These crustaceans vary in size, from 0,8cm to 8cm (0,3-3,1 inch) and come in a wide variety of colors. From white, to yellow, orange, red, and even purple. Some have very striking color patterns, like the Epimeria loerzae. The same species, like many others, has remarkable spikes on its back. This likely functions as both a defense against predators, and as a disruptive shape, which is a form of camouflage.
Most species are predators or scavengers, feeding on small crustaceans, brittle stars, spongers, sea cucumbers, plankton, and cnidarians.

When a worm or an eel is not enough

There is the gigantic deepwater worm eel! This species is 1,3m (50 inch) from head to tail. Other worm eel species are half as large and weigh only one-third compared to a gigantic deepwater worm eel. It’s so rare that only one species has been found so far near Philippines. It’s even so rare that there are no copyright free images available, nor any videos on the subject, so you will have to do with a link to the image. It has an interesting coloring and texturing on its body to say the least. And looking at its streamlined body, I’m pretty sure that its a gracious swimmer!

Translucent eel

Well, this was supposed to be a top 7, but heck, I had to add this beauty! Ever seen an Leptocephalus? It’s an eel larva which are rarely seen in this stage. The one in thevideo below was filmed by two scuba sivers called Barry Haythorne and Rob Ruthgers near Bali. Just look at it! It’s simplicity and beauty is stunning!

I mean, this animal consists out of a head, a simple gut tube (the stripe down the middle) and the surrounding body that consists out of a clear gel that’s no more than glucosaminoglycan (from this substance the mature fish will grow collagen tissue and cartilage). They sometimes say ‘less is more’ and this is a perfect example.

Many different eels go through this larval stage and they all roughly look the same. Their heads may be relatively larger, or their bodies shorter, depending on the species. The larval stage on its own is not remarkable, the size of it is, and also the time they spend in their larval stage, which is up to three months.
They most likely feed on marine snow, which are small particles drifting in the ocean. No other types of food have been found inside their guts,
These so-called glass eels live in the upper 100 meters of the ocean and are mostly active at night. They can be seen though in deeper areas during the day.

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