The body of the colossal squid

A colossal squid has three main body parts: the mantle and
fin, the head, and a circle of arms and tentacles.

The mantle

The main body of the squid is called the mantle, which fits like a sheath over the internal organs. This colossal squid's mantle is about 2.5 metres long and about 982 millimetres wide, almost the same diameter as a truck tyre — which would make pretty big squid rings!

The mantle is made up of muscle and skin. Small pigment-containing cells, called chromatophores, give the skin its reddish-pink colour. When these cells contract, the skin appears paler. The reddish skin of the colossal squid in the tank is peeling off the mantle surface in some places.

When the squid was caught and still alive, it was bright red, which may be a sign that it was under stress.

Gladius, or pen

All molluscs have a shell. The colossal squid has an internal shell called the gladius. The gladius is a rigid internal structure that supports the squid's body and runs through the upper part of the mantle, between the paired tail fin. It is made of chitin — a tough, protective, and semi-transparent substance, which is primarily a nitrogen-containing polysaccharide. The gladius is easy to remove when dissecting a squid, and looks like a long piece of plastic.

Tail fin

The paired tail fin is attached to the upper surface of the mantle and is made up of muscle. The colossal squid swims forward through the water by undulating the fin longitudinally.

The fin is unusually massive and muscular (1,183 millimetres long and 982 millimetres wide). This probably enables the colossal squid to move forward quite rapidly in short bursts when attacking prey. In most squid, the paired tail fins are used more for changing direction than propulsion.

Funnel or siphon

The funnel, or siphon, is a muscular structure located on the ventral surface of the mantle. It has several functions, including respiration and discharge of wastes. The colossal squid also uses the funnel to help it move in the water. When the mantle expands, water is sucked into the squid's mantle cavity through the mantle opening around the head. Oxygenated water then bathes the gills for respiration.

When the mantle contracts, water is squirted out through the funnel along with waste products. The squid can move backwards using jet propulsion by rapidly shooting water out through the funnel.

Image 01
The thawed colossal squid, star of the show, before being fixed in formalin. This photo was taken before the specimen was turned over, so the mantle and fin are upside down (dorsal view).
Image 02
Dorsal view of the colossal squid.
Illustration by Anton van Helden.
Image 03
Lateral view of the colossal squid.
Illustration by Anton van Helden.
Image 04
A ventral view of the mantle as Dr Steve O'Shea, Dr Tsunemi Kubodera, and Dr Kat Bolstad count the number of suckers and hooks on the arms.
Image 05
Dr Olaf Blaauw, Mark Fenwick, and Dr Kat Bolstad look inside the mantle of the smaller, dissected colossal squid.
Image 06
The gelatinous skin covering the squid's muscular mantle is delicate, and starts to come off as the squid thaws.
Image 07
The muscular mantle is covered by a delicate, gelatinous skin. Chromatophores on the skin contain red pigment.
Image 08
Dr Olaf Blaauw, Dr Tsunemi Kubodera, and Dr Kat Bolstad measure the colossal squid's head.
Image 09
The team holds up the thawed colossal squid in the tank. The mantle and tail fin are twisted, showing the ventral side.

Clockwise from left:
Dr Tsunemi Kubodera, Dr Kat Bolstad, Mark Fenwick, Dr Olaf Blaauw, Dr Steve O'Shea.
Image 10
Ventral view of the muscular paired tail fin of the colossal squid.
Image 11
Chris Paulin holds the gladius removed from the smaller colossal squid.
Image 12
A head-on view of the colossal squid showing the funnel.

Digital reconstruction