Stopping the rot
Once the colossal squid was thawed, it had to be stored in a liquid preservative to stop the tissues rotting. When they are stored, biological specimens, just like food, can become contaminated with microorganisms which make them decompose.
To prevent this soft-bodied museum specimens are often stored in a preservative such as formaldehyde. Formaldehyde is a pungent gas consisting of hydrogen, oxygen and carbon. It is available as an aqueous solution known as formalin. This is what the colossal squid was preserved in.
Formalin is toxic, so the scientists needed to take care using it. They had to wear full protective gear, including respirators, when adding it to the tank.
The team also injected formalin into the arms and outer body of the squid. Once the formalin was pumped into the tank, the lid was put in place, and the squid was left in the 6,000 litres of solution to 'fix' for two months.
Neutralising the acid
Pure formalin is acidic and would have dissolved the hooks and beak of the squid. To stop this happening, the liquid in the tank was buffered with bicarbonate to keep it as neutral as possible.
The pH level of the storage solution was monitored every three hours for the first 24 hours. After that, the pH was checked every three days.
Changed during preservation
During the preservation process, the colossal squid changed. The tissues became harder and less flexible, and there was some loss of colour.
Glycol for public display
For safety reasons, formalin cannot be used in public spaces. So for public display in the Te Papa exhibition spaces, the formalin had to be replaced with another liquid preservative. The team decided to use glycol. Propylene glycol is a colourless, nearly odourless, syrupy liquid derived from natural gas. It is an antifreeze as well as a preservative.
Learning by experiment
As no one has ever used glycol to store such a large biological specimen for a long time, this is a bit of an experiment! The team will have to monitor the squid carefully over the next few months. They will have to take samples of the storage solution regularly, and the tank has been designed to allow this to happen.