The legend of “Kraken” is not totally false. In the depths of the Antarctic Ocean lies the refuge of a creature similar in size and appearance to myth. The colossal squid (Mesonychoteuthis hamiltoni). Little is known about this animal, but this is enough to fascinate you, the reader.

The colossal squid is known as the largest invertebrate of our planet in terms of mass (495 kg), and the second largest in length (the giant squid takes first place). The species of squid closest to this squid are very fragile and transparent beings, known by the name of “glass squid” not exceeding a couple of centimeters, resembling plastic bags or jellyfish, in everything different than M. hamiltoni, a large animal with well developed muscles and claws/hooks emerging from the suction cups in the tentacles. But they have in common the fact that they have a fluctuation chamber [1] and the presence of photophores [2].

Despite their appearance, these animals serve as a meal for others in the Antarctic Ocean, such as Albatrosses, cetaceans and even fish. Albatrosses, seabirds that can weigh up to 9 kg and plunge up to 20 meters deep are a predator (at least) out of place for a half-ton animal that lives up to 2500 meters below the surface. Most likely, these birds, like ocean vultures, feed on already dead (or dying) squids that eventually float to the surface. Cetaceans seem to be the least surprising predator, since it is often imagined in the fiction fights between sperm-whales and this animals. Finally, we have the fish, more precisely the species Dissostichus mawsoni (antarctic toothfish), which are involved in mutual predation (fish -> squid and squid -> fish) as an alien (squid) vs. predator (fish) duel.

[1] with the same function as a swimming bladder

[2] light emitting organs

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Source: Rosa, R., Lopes, V.M., Guerreiro, M., Bolstad, K. and Xavier, J.C., 2017. Biology and ecology of the world’s largest invertebrate, the colossal squid (Mesonychoteuthis hamiltoni): a short review. Polar Biology, pp.1-13. doi: 10.1007/s00300-017-2104-5

Author: Miguel Guerreiro