I’ve always been fascinated by cuttlefish. Their calcium carbonate internal “shells” were once a common sight on Southsea beach (on England’s south coast where I lived when my girls were young) and were collected and used to keep our budgies healthy. Mekon seemed to enjoy his, although, looking back on it, I can’t help thinking it was cruel to keep birds locked up in a little cage. Cuttlefish have blue-green blood due to it being based on copper rather than, like ours, iron. In the same way that our blood is a similar colour to rust (iron oxide), the blood of octopodes is the colour of copper carbonate which is the greenish surface that forms on bronze statues when they’re exposed to the rain