2.3 Tissue sample collection
Immediately after each behavioural trial, squid were euthanised with AQUI-S (1:1000). The head was separated from the mantle, rinsed in distilled water, and blotted dry. The skin, tentacles, beak, and buccal mass were removed and the eyes and central nervous system (CNS, containing the oesophagus running through the middle) were dissected and snap frozen in liquid nitrogen within 4.18 ± 0.55 (mean ± SD) minutes after euthanasia. Tissues were then transferred to -80OC for storage. This study followed the animal ethics guidelines at James Cook University (JCU animal ethics number A2644).