For this publication, I'm doing things a little differently. As the one who suggested the ocean publication theme several months ago, while I know there are plenty of awesome research articles to explore, I had something more varied in mind. You see, I know way too much about fish, and I'm about to make that everyone's problem. I got a resounding yes in response to my request to, and I quote, "terrorize the readers with deep-sea nasties", so you're all in for it now.
I want to preface this by making it clear that I genuinely love the ocean and all the species in this article, freaky physiology and all. This article is meant to poke some fun at the more frightening denizens of the deep and to hopefully pique your curiosity. That said, the deep is a very alien place, and this article might not be for everyone (arachnophobes be warned). Despite this, the majority of readers should find the material interesting, so I encourage you to stick with me for this deep dive!
Now, I imagine you're already thinking about some of the more charismatic deep-sea species. Well, as cool as the vampire squid and the angler fish are, I want to cover some more obscure creatures (though I will give you bonus points if the coelacanth came to mind). For your sake, however, we’ll begin with a more familiar face.
The goblin shark, Mitsukurina owstoni, is known to cruise open waters beyond 1,300 meters (over 4260 feet) below the surface. Sightings of the shark are scattered across the Pacific, Atlantic, and Indian Oceans. One of the shark’s most iconic features is its long snout, known as a rostrum. The structure is studded with pores which lead to special sensory organs. These organs, called ampullae of Lorenzini, allow the goblin shark to sense the electric fields emitted by its prey. Perhaps even more unique than its impressive snout, however, are the goblin shark’s jaws. In the deep, creatures often go months between meals. As a result, many deep-sea species have evolved means of ensuring their meals don’t escape, and the goblin shark is no exception. It is one of the few shark species whose teeth are still visible even when its mouth is shut. Long and needlelike, these teeth are suited to latch firmly into the shark’s prey. Furthermore, its mouth is highly protrusible (extendable). At rest, the shark’s jaws sit retracted to a position under the shark’s eyes. When it detects prey within range, it will eject its jaws faster and farther than any other known shark species, snatching up its prey in a fraction of a second. This feeding tactic is appropriately called slingshot feeding, during which the goblin shark’s jaws can extend up to 9.4% of the shark’s body length at speeds of 3.1 m/s. Like a demented metal detector, the goblin shark will sweep the sea with its sensitive rostrum in search of fish, squids, and some pelagic crustaceans (swimming crustacean species). When it detects prey beneath its nose within range of its grasp, it will sling its jaws forward to capture its meal. Its hunting tactics are as specialized as they are deadly, which explains the shark’s monstrous appearance.
How about another ugly mug to pique your interest? With an expression encapsulating unadulterated anxiety, the telescope fish has a face only a mother could love.
Gigantura chuni is found around the world in tropical and subtropical oceans, ranging from depths between 500 to 2000 meters (1640 to 6560 feet). Like the goblin shark, the telescope fish boasts some unique physical features, the most prominent being its tubular eyes. The fish uses these highly-adapted eyes to hunt prey in the twilight zone, waiting as an ambush predator. The telescope fish takes advantage of the light filtering down from the ocean’s surface. It will hang vertically in the water column, using the faint light and its fantastic eyes to pick up the silhouettes of prey. From there, its expansive jaws enable the telescope fish to swallow prey larger than their own body size. Especially large catches are folded in half and stored within the fish’s expandable stomach. Such adaptations are well-suited for a world where the next meal is never guaranteed.
Another interesting bit of trivia about the telescope fish is that its larval stage looks nothing like its adult form.
First discovered in 1954, the larval telescope fish was thought to be an entirely different species from the adult, which was discovered in 1901. Larval fish forms failing to resemble their parents has actually been a recurring problem for marine scientists.
Now, jaws and teeth are all well and good, but they aren’t the only means of survival in the depths. The hagfish is well acquainted with this fact, considering its lack of the former.
Hagfish belong to the superclass Agnatha, meaning “jawless fish”, and are descendants of some of the earliest marine vertebrates. They lack proper bones, so their skeleton is made of cartilage. In place of bony jaws, hagfish have a slitlike opening bordered by two rows of keratinous teeth. Resembling eels, hagfish possess a long, sinuous body that can grow anywhere between 16 to 40 inches long, depending on the species. Their appearance earned them the affectionate nickname “slime eel”. The eel part is self-explanatory, but what about the slime? Turns out it's the hagfish’s special skill.
The body of the hagfish is lined with pores that secrete truly impressive amounts of slime. This slime acts as the fish’s main defense, clogging up the mouth and gills of predators who try to take a bite out of it. The slime also lubricates the hagfish’s body, allowing it to slip away from danger. Hagfish produce so much slime that they actually “sneeze” it out and tie themselves in knots to shed the excess. If they didn’t, they would end up choking on their own secretions. Sounds pleasant.
Fitting their slimy lifestyle, hagfish are opportunistic predators as well as scavengers. They prey on fish and marine invertebrates, especially those which are crippled or already dead. They also frequent whale falls, which are the sunken corpses of deceased whales. Super fun fact: since they have no jaws, hagfish can’t really rip into their prey as easily as other fish, so they will often start their meal by going for the softest tissue first. I’ll leave you to extrapolate from there. Another super fun fact: Hagfish have been known to attack fish caught on lines or in nets. They’ll bore their way into the fish’s body, eating them from the inside out. Needless to say, fishermen often aren’t too fond of them.
Hagfish have a preference for cold seawater at depths below 1,300 meters (4260 feet). They are partially benthic in nature, meaning they spend a lot of time on the seafloor. They can be found burrowed into soft sediment with only their heads left exposed.
So the consensus is no jaws, no problem as far as the hagfish is concerned, but what about the other end of the spectrum? Well, can you recall a time when you took a large helping of something delicious only for someone to nag you for having eyes bigger than your stomach? In the case of one fish, however, this is hardly ever true. As far as the gulper eel is concerned, any food is fair game.
The gulper eel, also called the pelican eel, is aptly named for its massive mouth, which takes up the majority of the eel’s body size. Scientific name Eurypharynx pelecanoides, the gulper eel resides at depths between 500 and 3,000 meters (1640 to 9840 feet). There, it can grow to 3 to 6 feet in length. To hunt, it uses a pinkish-red bioluminescent lure on the tip of its tail. Its highly specialized body with a long, ribbon-like tail and almost nonexistent pectoral fins make the gulper eel ill-suited to chase down its prey, hence the ambush approach. When prey is lured close enough, the eel uses its mouth as a fishing net to scoop up its meal. Like the telescope fish, the gulper eel’s stomach can also extend to hold larger catches. Excess water swallowed along with prey is slowly expelled through its gills. Interestingly enough, the gulper eel’s diet mainly consists of smaller crustaceans and invertebrates as opposed to larger prey. Its mouth is well suited to scoop up groups of smaller creatures, but in times of food scarcity, the gulper eel can also expand its diet to larger prey in order to survive.
As well as using it to grab a bite, the gulper eel has been observed using its mouth to defend itself against predators. When agitated, the eel takes in a mouthful of water and swells up like an angry beachball. This makes the eel appear much larger to predators and may discourage their advances.
We’re getting to the thick of it now. The species that have been discussed thus far are strange but not unheard of to the general public. These last three, on the other hand, are true oddities. Take the basket star, for example.
A living mass of twisted tentacles, the basket star can be found as deep as 550 meters (1800 feet) down in colder waters. It dwarfs most other starfish lookalikes with arms that can measure a meter in length. Speaking of its arms, the basket star’s appendages are covered in tiny hooks which the creature uses to capture its prey. It gets the name “basket star” from its appearance as well as the way it hunts. While anchoring its body to the seafloor, the star splays its branched limbs outwards to form a basket. Any jellyfish, small shellfish, or zooplankton that get snagged by its hooks are dragged to the basket star’s mouth. The basket star’s arms can also act in its defense. When in danger, the star can wrap itself up in its arms to form a tight, hooked ball, dissuading would-be attackers.
We're sticking to the theme of tentacles for this next creature (because who doesn’t like tentacles). Say hi to Slenderman’s long-lost cousin.
The bigfin squid is a phantom of the depths, living deeper than any other known squid species at as far as 4,735 meters down. For perspective, that’s three miles below the ocean’s surface. The big fin squid was only discovered relatively recently, with the family being officially recognized by scientists only 20 years ago. Since its initial discovery, there have only been about a dozen confirmed sightings of the squid. From these few encounters, scientists have learned that the squid appears to hunt by hanging motionlessly in the water column. Near the base, each of its tentacles sports a unique elbow, allowing the squid to drape its arms like a ghostly curtain. It is unknown whether the squid hunts in open water or whether it drags its arms across the seafloor. Regardless, scientists believe that the big fin squid waits for prey to bump into its tentacles before snatching them up.
It’s hard to accurately judge the squid’s size given its skeletal shape, but the creature is likely larger than you think. Bigfin squids have been found to exceed 6 meters (20 feet) in length. The largest specimen on record measured 6.4 meters, its appendages taking up 6.1 meters of its length. Fun fact: Because there are only a handful of squid sightings it’s hard to tell, but some scientists believe that we have only ever encountered juvenile big fin squid. That means this phantasmal monster might get even larger than previously observed. A comforting thought, I’m sure.
And now, the moment you have been waiting for, it is my pleasure to introduce you to the strangest and most disturbing creature in this collection; the sea spider.
In my research, I have found the sea spider to be the personification of “but wait, there’s more”. For one, it looks as though the front half of a human rib cage gained life and started scuttling around. And swimming too, because despite their thin appendages they are able to propel themselves off the seafloor. Sea spiders are found across the world’s oceans, from tropical to polar waters as well as shallow depths to the seafloor. No one is spared from their insidious presence. Within their expansive range, they come in all sorts of sizes, from as small as a grain of sand to as large as a common housecat (what good pets they’d make). Sea spider is the name given to anything within the Pycnogondia class, of which there are a whopping 1,300 species! Most species have eight legs (though they can have more :D) and are equipped with a hard exoskeleton. In addition to their legs, sea spiders sport several simple eyes, a pair of claws, and a pair of ovigers (modified legs) used for grooming and carrying their eggs. Perhaps you are wondering what the creature looks like on the inside. After all, where does something that skinny keep all its organs? Why in its legs of course! For example, its intestines extend all the way to the end of its legs. Oxygen then diffuses through its legs and into its intestinal pouches. A lovely way to breathe, and somehow, the way it eats is even better. Sea spiders prey on soft-bodied animals including jellyfish, worms, anemones, and nudibranchs. The prey needs to be soft because the sea spider uses its proboscis (a tubular mouthpart) to pierce its prey’s flesh and suck out its innards. This wonderful feeding method isn’t even guaranteed to be fatal, and thus the sea spider’s prey is sometimes left suffering long after it is caught. The consensus: sea spiders put several eldritch horrors to shame and they are now one of my favorite sea creatures.
Evidently, the deep ocean is filled with all sorts of alien creatures. A lot of people find deep-sea species to be scary or unpleasant, and I admit to putting their most unusual features at the forefront of their descriptions. However, it is important to remember that, weird or not, all the creatures on this list fill important roles in the ocean’s ecosystems. For instance, deep-sea scavengers like the hagfish help recycle nutrients trapped within detritus falling to the seafloor. They break up dead matter so it can cycle back through the ocean. Without the efforts of deep-sea scavengers, nutrients would become trapped in the deep away from the upper sea life. Sea creatures are just animals going about their lives. What seems strange to us is natural to them, and their unusual behaviors are more often than not borne out of necessity. The ocean’s abyssal depths are a tough place to live, so you can’t blame the residents for getting a little creative. In fact, that’s why you should find them interesting. The deep’s denizens have come up with an array of adaptations extending far beyond this article in order to survive. Deep-sea creatures are perfect examples of the ocean’s diversity and should be recognized for their interesting approaches to life.
Thanks for reading this special installment! I hope you enjoyed the freaky fish facts and that you have just maybe found a new favorite sea creature to add to your list.
Barras, C. (2019, December 3). Zoologger: The giant sea spider that sucks life out of its prey. New Scientist. Retrieved May 4, 2022, from https://www.newscientist.com/article/dn27978-zoologger-the-giant-sea-spider-that-sucks-life-out-of-its-prey/
Benningfield, D. (2016, November 27). Basket stars. Basket Stars | Science and the Sea. Retrieved May 4, 2022, from https://www.scienceandthesea.org/program/201611/basket-stars
The Editors of Encyclopaedia Britannica. (2019, February 12). Hagfish. Encyclopædia Britannica. Retrieved May 4, 2022, from https://www.britannica.com/animal/hagfish
Goblin Shark. Oceana. (2021, November 7). Retrieved May 4, 2022, from https://oceana.org/marine-life/goblin-shark/
Gulper eel. Gulper Eel - Deep Sea Creatures on Sea and Sky. (n.d.). Retrieved May 4, 2022, from http://www.seasky.org/deep-sea/gulper-eel.html
Magazine, S. (2012, October 17). 14 fun facts about hagfish. Smithsonian.com. Retrieved May 4, 2022, from https://www.smithsonianmag.com/science-nature/14-fun-facts-about-hagfish-77165589/
McGrouther, M. M. (2021, March 19). Goblin Shark. The Australian Museum. Retrieved May 4, 2022, from https://australian.museum/learn/animals/fishes/goblin-shark-mitsukurina-owstoni/
Monterey Bay Aquarium. (n.d.). Sea Spider. Montereybayaquarium.org. Retrieved May 4, 2022, from https://www.montereybayaquarium.org/animals/animals-a-to-z/sea-spider
Nakaya, K., Tomita, T., Suda, K., Sato, K., Ogimoto, K., Chappell, A., Sato, T., Takano, K., & Yuki, Y. (2016, June 10). Slingshot feeding of the goblin shark mitsukurina owstoni (Pisces: Lamniformes: Mitsukurinidae). Nature News. Retrieved May 4, 2022, from https://www.nature.com/articles/srep27786
Rabenold, C. (2021, November 12). Windows to the deep 2021: Southeast U.S. ROV and mapping. Bigfin Squid: Windows to the Deep 2021: Southeast U.S. ROV and Mapping: NOAA Ocean Exploration. Retrieved May 4, 2022, from https://oceanexplorer.noaa.gov/okeanos/explorations/ex2107/features/bigfin-squid/bigfin-squid.html
Telescopefish. College of Agricultural Sciences. (2018, March 30). Retrieved May 4, 2022, from https://fwcs.oregonstate.edu/150-species/telescopefish
US Department of Commerce, N. O. and A. A. (2011, July 5). Creatures of the deep: Basket star. Ocean Today. Retrieved May 4, 2022, from https://oceantoday.noaa.gov/creaturesofthedeep_basketstar/
Woods Hole Oceanographic Institution. (n.d.). Creature feature: Pelican eel. Twilight Zone. Retrieved May 4, 2022, from https://twilightzone.whoi.edu/explore-the-otz/creature-features/pelican-eel/