Giant Squid…

biology
This entry is part 1 of 12 in the series Animals

.It is rare for the giant squid (Architeuthis dux) to show up where it can be filmed. It was only photographed alive for the first time in 2004 although dead specimens have washed up on shore and been removed from the stomach of sperm whales (Physeter macrocephalus). The first film footage of a giant squid was in 2012.

Full-sized specimens are thought to be about 10 to 12 metres in length. The one in the video above is only about 4 metres long so it is probably still quite young. It is unusual to see one in such shallow water because by day they tend to live between 300 and 1000 metres down. They come nearer the surface at night but retreat back to the deep at dawn. They also spend more time nearer the surface when they are younger.

The squid’s body consists of a mantle (the part with the eyes and siphon), eight legs and two long tentacles. The arms and tentacles are lined with suckers each surrounded by a hard ring of chitin. They also have a hard beak at the opening of their mouths. When they capture prey in their arms they draw it towards the beak and tear off chunks. They produce a mixture of toxic and digestive chemicals that help to stun and dissolve their prey. They use the siphon to force out water, jetting them along at great speed.

The squid’s eye is the largest in the animal kingdom. Although it is not thought to provide colour vision, it is probably extremely good at distinguishing subtle differences in shade. At the depths at which architeuthis hunts there is very little light so large eyes would be a huge advantage.

Whilst giant squid pursue deep-sea fish and other squid as prey, their main predator is the sperm whale. Some juvenile squid may also be preyed upon by deep diving shark species. Much of what is known about the giant squid has been found out by studying sperm whales. Most sperm whales carry the scars of their encounters with the toothed suckers of their prey deep within the ocean.

Squid belong to the invertebrate phylum molluscs. All molluscs have soft bodies and many have one or more muscular feet, similar to the squid’s suckers. Sometimes they have shells made from calcium carbonate; indeed calcium is the metal element most plentiful in the squid’s body. So little is known about giant squid, despite their very wide distribution in the world’s oceans, that it is thought that the whole global population could all be the same species.

Questions…

  1. Suggest two other members of the phylum mollusc.
  2. Name one way in which a sperm whale is a typical mammal.
  3. Sperm whales have relatively small eyes. How might they track and pursue their prey under water?
  4. Name an enzyme present in human saliva.
  5. How do you think researchers know that squid eyes are not sensitive to colour?
  6. Calcium is the most plentiful metal element in the human body. Suggest another important metal present in humans and what role it performs.