Stress is not pain. Comment on Elwood and Adams (2015) 'Electric shock causes physiological stress responses in shore crabs, consistent with prediction of pain'. - Stevens ED; Arlinghaus R; Browman HI; Cooke SJ; Cowx IG; Diggles BK; Key B; Rose JD; Sawynok W; Schwab A; Skiftesvik AB; Watson CA; et al. (Biology letters, 2016)