page_title: Emotion in animals
section_title: Crayfish
hierarchical_section_title: Emotion in animals / Examples / Crayfish
caption_attribution_description: English: Procambarus clarkii9284477アメリカザリガニ 日本語: Procambarus clarkii9284477アメリカザリガニ
context_page_description: Emotion is defined as any mental experience with high intensity and high hedonic content. The existence and nature of emotions in animals are believed to be correlated with those of humans and to have evolved from the same mechanisms. Charles Darwin was one of the first scientists to write about the subject, and his observational approach has since developed into a more robust, hypothesis-driven, scientific approach. Cognitive bias tests and learned helplessness models have shown feelings of optimism and pessimism in a wide range of species, including rats, dogs, cats, rhesus macaques, sheep, chicks, starlings, pigs, and honeybees. Jaak Panksepp played a large role in the study of animal emotion, basing his research on the neurological aspect. Mentioning seven core emotional feelings reflected through a variety of neuro-dynamic limbic emotional action systems, including seeking, fear, rage, lust, care, panic and play. Through brain stimulation and pharmacological challenges, such emotional responses can be effectively monitored.
context_section_description: Crayfish naturally explore new environments but display a general preference for dark places. A 2014 study on the freshwater crayfish Procambarus clarkii tested their responses in a fear paradigm, the elevated plus maze in which animals choose to walk on an elevated cross which offers both aversive and preferable conditions (in this case, two arms were lit and two were dark). Crayfish which experienced an electric shock displayed enhanced fearfulness or anxiety as demonstrated by their preference for the dark arms more than the light. Furthermore, shocked crayfish had relatively higher brain serotonin concentrations coupled with elevated blood glucose, which indicates a stress response.  Moreover, the crayfish calmed down when they were injected with the benzodiazepine anxiolytic, chlordiazepoxide, used to treat anxiety in humans, and they entered the dark as normal. The authors of the study concluded "...stress-induced avoidance behavior in crayfish exhibits striking homologies with vertebrate anxiety."
  A follow-up study using the same species confirmed the anxiolytic effect of chlordiazepoxide, but moreover, the intensity of the anxiety-like behaviour was dependent on the intensity of the electric shock until reaching a plateau. Such a quantitative relationship between stress and anxiety is also a very common feature of human and vertebrate anxiety.
caption: The freshwater crayfish Procambarus clarkii
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