Book Review

Halloween Edition: Creepy Ocean Critters

Vampire Squid (Vampyroteuthis infernalis)

Figure 1: A vampire squid photographed by one of Monterey Bay Aquarium’s Research Institute underwater submersible.
Figure 1: A vampire squid photographed a Monterey Bay Aquariums Research Institute underwater submersible.

Although the name sounds fierce, the vampire squid is far from frightening. The vampire squid was originally given its monstrous name because of the dark, cape-like appearance of its webbed arms, the “spines” on its arms, and the blood-red coloration of the eyes in certain light (although blue when seen from submersibles – Figure 1). The Latin name of the species directly translates to “vampire squid from hell”. The vampire squid is relatively small, only reaching 13 cm in length (about the size of a soft football) and lives around the world in deep temperate and tropical waters (~600 – 1200 m).

The vampire squid has some interesting and unique life history characteristics compared to other cephalopods. This is the only squid thought to live its entire life within oxygen minimum zones (waters with very low oxygen concentrations- in which many animals cannot survive). To cope with low oxygen, the vampire squid has a special protein in its blood (called haemocyanin – similar to our hemoglobin) which strongly binds to oxygen1. Additionally, the squid has a slow metabolism and frequently floats motionless in the water rather than actively swimming. Unlike most of its relatives, the vampire squid does not actively hunt live prey (nor does it feast on blood), but rather eats detritus (decaying matter, plankton, fecal pellets, etc.) which float through the water column2. Another recently discovered and unique characteristic: the vampire squid appears to reproduce multiple times over the course of its life (other cephalopods only breed once before dying) and may be very long-lived compared to shallow dwelling squid relatives3.

The vampire squid has a photophore on each fin and at the tip of each arm, which produce beautiful bioluminescent displays. To escape predators, the vampire squid will wave around its glowing arms in a dizzying dance. The squid then emits a bioluminescent mucous (similar in function to black ink emitted by most cephalopods) to further confuse predators and escape unnoticed.

References:    1. Seibel et al., 1999 2. Hoving and Robison, 2012 3. Hoving et al., 2015

The Oarfish (Regalecus glesne and Regalecus russellii) –

Figure 2: an oarfish found washed ashore.
Figure 2: an oarfish found washed ashore. The fish is so large is cannot be brought in by just one person!

Out of all of the animals on this list, this one sounds the most docile. But do not be fooled – this is the fish that inspired a large number of sea-serpent myths among sailors. The oarfish is the longest bony fish on earth, with specimens reaching 8 m in length (that’s over 25 feet long!) and weighing up to 600 lbs (Figure 2).

It is thought that the two species may stay in deep-water (around 1000 m)4. The oarfish may come to the surface occasionally but the majority of the large fish seen swimming in the shallows are in distress or dying.

These “sea monsters” appear to have the remarkable ability to self-amputate5. This is similar to examples of lizards shedding a tail in order to escape a predator; however, scientists do not believe that the oarfish is using this remarkable body truncation to avoid predators. The reason behind this mysterious behavior is unknown.

Little is known about these giant creatures. This is largely because we do not have many encounters with oarfish- especially while they are alive. So do not be worried about running into a sea serpent on your next beach adventure. If you are still scared that you may be one of the lucky few to lay eyes on a living oarfish – be aware that these fish have no visible teeth and eat only plankton.

References: 4. Benfield et al., 2013 5. Roberts, T. R. (2012). Systematics, Biology, and Distribution of the Species of the Oceanic Oarfish Genus Regalecus:(Teleostei, Lampridiformes, Regalecidae). Publications Scientifiques du Muséum.

The Goblin Shark (Mitsukurina owstoni)-

Figure3: Goblin shark (Mitsukurina owstoni).
Figure3: Goblin shark (Mitsukurina owstoni).

This shark is commonly referenced as one of the creepiest animals in the ocean. Its small eyes, long, flat snout, and jagged teeth projecting from the lower jaw give this fish an alien-like appearance (Figure 3). This is a relatively rare shark and we actually do not know much about its biology. The larges goblin shark found to date measured in at 12.6 feet long. No need to worry about encountering one of these gnarly-toothed creatures on your next visit to the beach – goblin sharks are believed to be bottom-dwelling (demersal) fishes living between 95 – 1300 m6. You would be very lucky to encounter one of these rare sharks.

What’s up with the weird snout? Like all sharks, the goblin shark can sense electric currents using special organs (ampullae of Lorenzini) which allow them to detect prey and orient to the earth’s magnetic fields. It is hypothesized that the odd-shaped snout is used to increase the goblin shark’s sensitivity to electric pulses- likely helping them to locate prey in the dark. As for that crazy jaw- when goblin sharks have been observed alive, the jaws do not normally stick out. These sharks use their extremely protrusive jaw to help catch their prey, which appears to be mostly fish and squid7. One live specimen was caught and held on display at the Japanese Aquarium in 2007. The shark only survived in captivity for 2 days, however, interesting footage on the living specimen can give researchers insight into this poorly understood animal.

References: 6. Rincon et al., 2012  7. Yano et al., 2007

Additional information can be found at: Florida Museum of Natural History and

Black Sea Devil (Melanocetus johnsonii) –

Figure 3: Melanocetus johnsonii female with attached male (hanging off of the belly). Specimens held at the British Museum of National History. Image credit : E.A. Widder-
Figure 4: Melanocetus johnsonii female with attached male (hanging off of the belly). Specimens held at the British Museum of National History. Image credit : E.A. Widder

There are actually 6 species of Black Sea Devils (belonging to the family Melanocetidae). Melanocetus johnsonii is one of the most abundant species in the family, found worldwide in deep waters between 500 – 1500 m. It may look like this fish is going to come swallow you whole with its gaping mouth and elongate teeth, but do not be afraid- this anglerfish only grows to 135 mm long8– probably about the size of your phone.

Melanocetus is in the group of anglerfishes called the ceratoids. These ceratoid anglerfishes typically have dwarfed males with females being much larger (Figure 4). Males have larger eyes and nostrils than females, which are used to find potential mates in the vast, dark ocean. In many ceratoids, these dwarfed males will actually attach to the female (often times fusing with her body and becoming parasitic), essentially acting as her personal egg fertilizer whenever she is ready to mate. In the sea devils, the males attach, but do not fuse to the female- serving as the first example of a non-parasitic attachment in ceratoid anglerfishes9.

As with other ceratoids, the black sea devil is a sit-and-wait predator. It uses a bioluminescent lure to attract prey (just think of finding Nemo). Bioluminescent bacterial symbionts (bacteria living within the blub of the lure) allow the fish to produce light10.


References: 8. Cowles and Childress, 1995 9. Pietsch, 2005 10. Hulet and Musil, 1968

Zombie Worm (Osedax worms)-

Figure 5: Osedax worms colonized on a whale carcass (left) showing the red plumes (gills). A female Osedax worm (right) showing the green “roots” which burrow into the bone.
Figure 5: Osedax worms colonized on a whale carcass (left) showing the red plumes (gills). A female Osedax worm (right) showing the green “roots” which burrow into the bone.

Zombies are real- but they do not feast on living animals, and certainly will not be turning you into a flesh-eating monster. The genus of worms, Osedax, was recently discovered in 2002, colonizing a decaying whale carcass11 (Figure 5). Turns out these worms will eat just about any type of bone they find in the nutrient-limited deep sea12. But they don’t “eat” in the same way we are accustomed to. These small (2 – 7 cm) worms do not have a mouth, a stomach, or an anus! They secrete an acid through their skin, and with the help of symbiotic bacteria, the worms are able to digest the fats and proteins within the bone. They burrow into the bone with their “roots”. Only the females burrow into the bones- the males are dwarfed and non-feeding. They live inside the females, acting as sperm repositories – simplifying the problem of finding a mate in the barren deep-sea. As many as 111 males have been found in a single female!

Since the discovery of the first Osedax species just 13 years ago, over 12 new species have been found. To learn more about this weird animal and how it was discovered, read this story from Monterey Bay Aquarium’s Research Institute.

References: 11. Rouse et al., 2004 12. Rouse et al., 2011


Leave comments to let me know what you think of these “scary” animals living in our oceans or if there are other creepy marine critters you would like to learn more about!





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