The twilight zone, also known as the Mesopelagic zone, is the midwater region of the oceans. At depths between 650 and 3,000 feet (200-800 meters) below the surface the sunlight is barely a glimmer; to the human eye it’s virtually darkness. That is where it gets it’s name “twilight zone”. To add to the feeling, the water is a frigid average temperature of 40°F (4°C). Residing in these waters are creatures beyond your wildest dreams (and, perhaps, nightmares).
“Everything that lives here has amazing adaptations for the challenges of such an extreme environment.” -Heidi Sosik, ocean scientist
So without further ado, may I introduce to you…a few of the most intriguing twilight zone inhabitants! Each wild creature is accompanied by a mesmerizing video for you to see just how special it really is.
The Rainbow Maker
A Ctenophores (also known as comb jellies, sea gooseberries, sea walnuts, or Venus’s girdles) is essentially a rainbow making jellyfish. Although technically it is not a jellyfish, rather, a comb jelly. They can be found all over the world. They come in many different forms (some are flat, some are rounded, some have lobes, some are shaped like medusa heads) and range widely in size, from a few millimeters to several feet.
Comb jellies might be all kinds of shapes and sizes but they do share a couple similarities. They are all translucent blobs with eight rows of swiftly beating cilia – minute, hair like structures that look like tiny combs. These cilia are what the jellies use to swim. This type of locomotion does more than just get the jelly from A to B. As their cilia wave they retract light, producing a rainbow-like effect. In other words, the movement of the hair like structures creates a rainbow lighting effect.
The Built-in Lure Fish
Anglerfish can be found worldwide. They have a mouthful of creep jagged, translucent, incredibly sharp teeth. Most are small but some (only the females) can grow to be three feet in length and weigh up to 110 pounds. The feature that makes them exceptionally strange is their built-in fishing rod which is actually a piece of dorsal spine that juts out above their mouths.
At the end of the rod is a fleshy bit covered with bioluminescent bacteria living on it. It looks like a glowing bubble and it acts as a lure, attracting crustaceans, fish and other prey. When their victim is in striking distance the fish opens its mouth nice and wide and the meal just swims into the trap. Unbelievably, it can devour something twice its size. Well, only the female can.
Actually, the males are much smaller and don’t even have a fishing rod! In order to survive they latch onto females with their teeth. And here’s where it gets really bizarre, the male will remain latched on for so long that the fish end up fusing together at the blood-vessel level and the male gives up all its internal organs (even its eyes) keeping only its testes. It is common for one female to host six or more males for life. Which is quite a long time to be fused to a group since they can live up to 24 years.
The Gelatinous Vacuum Chain
Salps range from about half an inch to 4 inches in length. The way they move is the way they eat. These translucent barrel-shaped animals propel themselves through the twilight zone by sucking water in one end and pushing it out the other. Then as the seawater moves through them, salps consume the phytoplankton particles floating in it.
Their lifespan is short – only a few months long. They begin alone then interlink to form complex chains of colonies meters long. They flow together in fascinating ways. Normally, each salp moves at its own pace, at ease, pulling the chain along with incredible efficiency. But if there is a strong current or if they are under attack by predators, the salps in these chains will move in a coordinated fashion.
The Squid-like Worm With Straw Tentacles
The squidworm is 4 inches long with 10 tentacle-like appendages, eight of which comprise its respiratory system. Included in these 10 tentacles are 2 brilliant spiraling yellow ones that they use to help them eat by sucking in little particles of marine snow – organic material that float through the twilight zone.
It has a tapered body with a color that transitions from black to brown. The muscles just underneath its skin glow a shimmery, iridescent pink. Along the side of its body are glittery bristles like fins that flutter, propelling it forward like a set of oars.
Scientists think the squidworm may be a transitional species. Meaning, it is the missing link between species that reside solely in the seafloor’s mud and those that live in the water column but never go to the floor.
The Light Communicator
Lanternfish range from 1-12 inches in length. They are small but they are many. They travel in massive schools found all over world. Masses so large, they’re as tall (thick) a two-story house. These are the fish that have been known to cause a phantom bottom – when something is mistaken for the ocean floor by sonar. It is possible that they make up 65% of the fish biomass in the sea.
There are around 250 different species, each possessing it’s own characteristic pattern of photophores – their bioluminescent blue, green and yellow organs. These glowing dots are a form of underwater camouflage called counter-illumination. From a distance, the light they emit blurs their silhouette thus making it difficult for predators to see them well. Some scientists even think these photophore patterns may help lanternfish communicate, and potentially pick mates.
The Red Lantern
Atolla’s are typically one to eight inches in diameter. Their vivid deep red color is a protective feature – it makes them practically invisible to their predators. These creatures are also found all around the world.
They typically have 20 marginal tentacles (and one hypertrophied tentacle which is larger than the rest) that extend from their ring-shaped core used to help them move and snare prey, catching food as it floats by. Here the incredible part, when their prey touch the tentacles, the Atolla produces bright, flashing circles of blue bioluminescence. Aquatic animals find the spectacle very alluring and are pulled right in to the trap. Like they say, “curiosity killed the cat”.
This last one is a bonus. It is not a twilight zone sea creatures but it deserves to be in the mix!
The Glittery Rainbow Sand Striker
This is Eunice aphroditois, also known as the bobbit worm, can grow up to 10 feet long but the only part of it you’ll see is the top of it’s head. This disturbing creature digs itself into the sand exposing a few inches of its body, never more, and waits. It is brainless, boneless, and purely relays on its senses to feed.
The bobbit worm senses passing prey using its five antennae. It snaps down on them with supremely muscled mouth parts, called a pharynx. The speed and strength of it can literally split a fish in two. But weather or not that happens, dead or alive, once caught the prey is yanked into the worm’s burrow and into untold nightmares. There is speculation that the eunicid injects some narcotizing or killing toxin in their prey animal, such that it can be safely ingested (especially if they are larger than the worm) and then digested through the gut.