Every summer opalescent squid (Doryteuthis opalescens) swarm together and lay masses of eggs. Opalescent squid tend to reproduce near the end of their life span, so in addition to finding eggs washed up on the beach, it's not uncommon to find the desceased parents as well. This particular washed up individual was fresh enough that its colour changing cells were still firing!
Cephalopods (including squid, octopus, and cuttlefish) are covered in specialized cells called "chromatophores." This close-up video shows these cells in action. Chromatophores are how cephalopods such as squid and octopus are able to change colour so rapidly. Each cell complex has muscle and nerve cells that cause the chromatophore to expand and contract. By controlling the diameter of the cell certain optics are altered, resulting in a change in reflected colour. The changes can happen incredibly quickly and are important for cephalopod camouflage and communication.
