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Halloween Under the Sea

Atualizado: 9 de dez. de 2020

English Edit Carla Elliff

How about some ocean “monsters” to get into the mood for Halloween?!

The undersea world is composed of an immense diversity of organisms. From the tiniest planktonic critter to the huge blue whale, from the cutest animals like the Dumbo octopus to the ugliest ones like the blobfish (just don’t forget “Ugly animals need love too!”). And, on the month of October, when we celebrate Halloween, we decided to put together a list of the scariest animals found under the sea. We hope you enjoy this piece and that it may inspire you to create some very original costumes in the future!

Dumbo octopus (left) and Blobfish (right)

Humpback Black Devil

In 1995, the cover of Time’s magazine featured the humpback black devil, a species of anglerfish that later would become a symbol for the deep sea. This fish is an abyssal species, known also by its scientific name Melanocetus johnsonii and belonging to the Lophiiformes order. The humpback black devil is found at mesopelagic depths in tropical and temperate waters all over the world. It has a sort of “fishing rod” with a bubble on the end that emits light, acting as bait and luring prey towards is terribly sharp teeth. The species’ glowing light is possible thanks to a symbiotic relationship between the fish and bioluminescent bacteria.

Male and female anglerfish are very different from each other. Females can measure up to 20 cm in length and have very big heads and mouths. Males on the other hand, have a much simpler body and are much smaller than females (measuring only up to 2.9 cm). Since they are incapable of surviving alone, they live as parasites on the females. Once a male finds a female, he bites on her belly and fuses into her body, receiving nutrients and blood supplied from her in exchange for a permanent supply of spermatozoids.

Researchers from the Monterey Bay Aquarium Research Institute, in California, have recently been able to film a 9-cm long female. The footage was taken at 600 m in depth in the Monterrey submarine canyon off the coast of California. This was the first record of the species in its natural habitat.

This mysterious predator has also starred as a movie villain. If you’ve watched Finding Nemo (Pixar Animation, 2003) you probably remember Dory and Marlin encountering this monstrous fish. In the film, while lost in darkness, they are lured by the humpback black devil’s light-bait. As soon as they realize this monster was behind them, they quickly escape this ferocious predator and continue on with their search for Nemo.

Vampire Squid

The vampire squid (Vampyroteuthis infernalis) is a cephalopod and the only living representative of the Vampyromorphida order. It is a small animal, reaching up to only 28 cm. The vampire squid inhabits deep waters (normally between 600 and 1200 m) in temperate and tropical regions of the Pacific, Atlantic and Indian oceans. At these depths, sunlight is either weak or completely absent, oxygen levels are low and temperatures vary between 2 °C and 6 °C. Although the vampire squid has a very low metabolic rate and is able to live under extremely low oxygen conditions, this animal is able to move surprisingly fast. They use their fins to move around instead of jet propulsion as other squids.

Though scarce, research on this species has shown that they feed on copepods, shrimp and cnidarians, but most of their energy is obtained from detritus (non-living particles that originate from the upper layers of the ocean and precipitate to the deep). Vampire squid are prey mainly for pinnipeds (seals, fur seals, sea lions and walruses), whales and benthopelagic fish, given that beaks of this species have been found in the stomach of these groups.

The species name means “vampire squid from hell” and it was chosen because of some of the morphological characteristics of this animal, such as its dark skin, the membrane it has between each tentacle that looks like a cape, and its red eyes (depending on the light). For the naturalist and explorer William Beebe (1926), the vampire squid is "a very small but terrible octopus, black as night, with ivory white jaws and blood red eyes". Scary! But according to some behavioral studies, this species is a docile animal.

A very interesting reading suggestion is a book called Vampyrotheuthis infernalis. It was written by philosopher Vilém Flusser and biologist/artist Louis Bec, and mixes philosophy/science/fable to discuss how distant we humans are from animals.


The hagfish is part of the Myxini class and although it can be classified as a vertebrate, it does not possess any vertebrae or bones, as described by researchers Alysha Heimberg back in 2010 and Joseph Nelson in 2016. Theodore Uyeno, from the Valdosta State University (Georgia, USA), analyzed the DNA of these organisms and concluded that the hagfish is a vertebrate that lost the characteristic of using a spine. Instead of a spine, the hagfish has a cartilage-like rod (notochord) that in us humans is only present during our embryonic phase.

These animals are found in cold waters in both hemispheres. They are primitive creatures, similar to eels, with a cylindric and elongated body but without scales, and move like snakes. These animals do not have jaws or stomachs. However, they have several hearts and at least twice the amount of blood in their body than other fishes. Hagfish also have four pairs of detection tentacles located around their mouth. By the way, their mouth holds two parallel lines of strong sharp teeth that are attached to rough dental plates. Although they only have an upper dental arch, these animals have a powerful bite! Researchers have suggested that this fish is indeed able to bite, since it coils up into knots, especially near its head, and with this movement crushes its food in its upper dental arch. Hagfish are almost blind. They rudimentary eyes can only detect light. However, they have highly developed senses of touch and smell.

Nicknamed “marine vultures”, hagfish spend most of their life on the seafloor feeding off dead and dying fish. They also attack small invertebrates, but their favorite dish is whale carcass. Another intriguing characteristic of this animal is that they have been shown to absorb nutrients through their skin. Moreover, hagfish secrete a thick layer of mucous over their skin that acts as both a defense mechanism and also a hunting weapon.

The video below shows the moment when these fish find a carcass on the seafloor. It looks like some sort of voracious zombie attack! No doubt they deserve to be in our ocean monster list.

Goblin Shark

If you’ve ever watched MIB: Men in Black (Sony Pictures, 1997), you will probably notice lots of similarities between this animal and the aliens shown in the movie. This is Mitsukurina owstoni, also known as the goblin shark. This deep-water fish is broadly distributed and has been reported in the Pacific, Atlantic and Indian oceans. Its unusual appearance is very striking. A long and flat snout projects from the shark’s head like a spade and its protuberant mouth, with long and thin teeth, can either extend forward below the snout or retract to the same position as its eye. It is believed that this flat snout is able to detect weak electrical signals emitted by prey. Goblin sharks can grow up to 3.9 m in length and, according to stomach content analyses, researchers have found that this animal eats mainly fish, squid and crustaceans.

While this shark is not a gifted swimmer, it does have an interesting strategy to catch its food. Once it detects its prey, the goblin shark moves slowly towards it and attacks by projecting its jaw forward, suddenly and quickly, sucking the prey into its mouth.

Although this species is rarely captured, it is not considered a threatened species (considered to be of “least concern” status in the IUCN red list), since most times it is fished it is by mistake (bycatch) when using bottom trawls in deep waters, especially off the coast of Japan. In 2011, a goblin shark was accidently captured by a fishing boat off the coast of the state of Rio Grande do Sul. The specimen was donated to the Oceanographic Museum of FURG (Federal University of Rio Grande), making it the second of its kind in a scientific collection in Brazil.

A fish dressed up in plastic is one of the scariest things in an under the sea Halloween party! Source: joelsaucedosaucedo/Pixabay.

Although some of these creatures of the depths are pretty gruesome, they are all important for the marine ecosystem. Can you imagine if they got together to through an under the sea Halloween party?! I bet the scariest costume for them would be of people and plastics, since these are two of the biggest threats to their existence.

So, enjoy yourself today, but remember to always do your bit so that we do not become real monsters to marine life. Happy Halloween!



HEIMBERG, Alysha M. et al. microRNAs reveal the interrelationships of hagfish, lampreys, and gnathostomes and the nature of the ancestral vertebrate. Proceedings of the National Academy of Sciences, v. 107, n. 45, p. 19379-19383, 2010.

NELSON, Joseph S.; GRANDE, Terry C.; WILSON, Mark VH. Fishes of the World. John Wiley & Sons, 2016.

Robison, B. H., Reisenbichler, K. R., Hunt, J. C., & Haddock, S. H. D. (2003). Light Production by the Arm Tips of the Deep-Sea Cephalopod Vampyroteuthis infernalis. The Biological Bulletin, 205(2), 102–109. doi:10.2307/1543231

ZINTZEN, Vincent et al. Hagfish feeding habits along a depth gradient inferred from stable isotopes. Marine Ecology Progress Series, v. 485, p. 223-234, 2013.

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Denny Luyis
Denny Luyis
Oct 25, 2023

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