Colossal Squid - The Largest Invertebrate in the Animal Kingdom.

"File: Colossal squid in Te Papa.jpg" by Scotted400

The largest invertebrate in the animal kingdom is the colossal squid(Mesonychoteuthis hamiltoni) with an average weight of at least 500 kg and a maximum weight of 700 kg. Current estimates suggest that these squids usually grow up to a length of 10 meters but the maximum length can be 14 meters.

HABITAT

The colossal squid inhabits the deep cold waters of the Antarctic Ocean. The depth at which the individuals of the species are found depends upon their life stages. Young squids are found between 0 - 500 m, adolescents are found between 500–2000 m and adults are found between mesopelagic and bathyal zone.

BODY

Not only are they the largest squid species but also have the biggest eyes in the animal kingdom. Each eye is as big as a soccer ball with a diameter of 27 cm. The eyes have their own headlights i.e., they have light organs called photophores behind their eyeballs. These photophores provide enough light for the squid to see in its dark surroundings. The glowing of these light organs in the dark is an example of a phenomenon called bioluminescence.

Like all other squids, they also have a head, a mantle, a pair of gills, two tentacles, and eight arms but these are the only squids of the family Cranchiidae to have swivelling hooks on their tentacles and arms. The hooks on the arms and tentacles differ from each other as the hooks on the tentacles can swivel but those on the arms cannot. The colour of the skin is reddish-pink due to the presence of pigmented cells called chromatophores.

DIET

M. hamiltoni are carnivorous invertebrates. These are ambush predators. It is believed that their diet includes Patagonian toothfish, Antarctic toothfish, and Chaetognatha. One study also suggests the possibility of cannibalism within the species. Even though they have huge body, they consume very little food as it has a very slow metabolism.

PREDATION

Despite being giants, these predators are also preyed upon by other animals. The animals that prey upon the colossal squid include beaked whales, pilot whales, southern elephant seals, Patagonian toothfish, Antarctic toothfish, and albatrosses. These predators only consume the juvenile and young squids. The only predators that are known to prey upon fully grown squids are sperm whales and sleeper sharks.

SIGHTINGS

Although the colossal squids are the largest invertebrates, they are rarely sighted. The first colossal squid was discovered in 1925 and only 12 complete adults have been found since then.

To learn more about these animals, visit the official website of Te Papa Museum at https://www.tepapa.govt.nz/discover-collections/read-watch-play/science/colossal-squid