What s the world s largest invertebrate

Q. Just how big is it

A. At least up to 18m in length and up to 900kg in weight.

It holds another record: it has the largest eyes in the animal kingdom. They can grow up to 25 cm in diameter.

Q. At least 18m

A. Unfortunately very little is known about the giant squid. Sightings by sailors describing giant sea monsters were dismissed by the scientific community until relatively recently due to lack of evidence. However, specimens washed up on beaches have provided some basic information and confirmation that these giants do exist.

Q. If they're the biggest invertebrates, how come so little is known about them

A. The fact they live in the ocean helps them evade humans. Also, they live in the deepest parts of the ocean, rarely surfacing.

Squid are masters of evasion. They can change colour in a split second using pigment cells called chromatophores.

Q. How many arms does it have

A. This we do know. Even though there are 500 species of squid, ranging from just 2.5cm up to 18m, they all have the same basic body structure. They have eight arms, studded with two rows of suckers and two feeding tentacles. They move about the oceans either by moving their fins or by jet-propelling themselves by forcing water through their body, reaching speeds of up to 20 mph.

Q. What does the giant squid eat

A. Based on the stomach contents of specimens washed up on shore, we know they have a diet of mainly fish and other squid. A squid grabs food with its tentacles and tears it up into bite-sized chunks with its sharp, horny beak . A file-like radula then rams food down the throat and oesophagus, which passes directly through the brain to the stomach.

Because giant squid beaks are found in the stomachs of sperm whales, we know these huge creatures are also eaten - but they must put up quite a fight as sucker marks have been found on sperm whales' skins.

Q. What is an invertebrate

A. The animal kingdom is basically split into two groups: those with a backbone -vertebrates -and those without, the invertebrates.

Q. Is it significant that the world's largest invertebrate is a marine animal

A. Yes, the natural buoyancy of the water is essential in aiding the giant squid move around. However the giant squid isn't completely helpless and is able to partially support its own body using the gladius, a feather-shaped blade, which also acts as a site for muscle attachment.

Do you want to know what's the smallest, oldest or fiercest member of the animal kingdom Click here to ask.

by Lisa Cardy