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What do fish make of mirror images?
Julie K Desjardins1, Russell D Fernald
1Department of Biology, Stanford University, CA, USA. desjarjk@stanford.edu
Biology Letters
|May 14, 2010
Summary
Fish fighting mirror images show distinct brain gene expression, suggesting fear. This indicates fish recognize unusual stimuli, differentiating real opponents from reflections.
Area of Science:
- Neuroscience
- Ethology
- Animal Behavior
Background:
- Aggressive behavior in fish towards mirror images is common.
- Mammalian mirror responses can indicate self-recognition, but fish lack this ability.
- The cognitive processing of mirror images in fish remains unclear.
Purpose of the Study:
- To investigate if fish can differentiate between fighting a mirror image and a real conspecific.
- To compare molecular, physiological, and behavioral responses in these two conditions.
Main Methods:
- Comparison of molecular (gene expression), physiological (androgen levels), and behavioral responses.
- Measurement of immediate early gene (IEG) expression in specific brain regions.
- Control groups for baseline and real opponent interactions.
Main Results:
- No significant differences in aggressive behavior or circulating androgens were observed between mirror and real opponent conditions.
- Elevated immediate early gene (IEG) expression was found in brain areas homologous to the amygdala and hippocampus in fish fighting a mirror image.
- These brain regions are associated with fear and fear conditioning in other species.
Conclusions:
- Fish exhibit differential brain activation when confronting a mirror image compared to a real opponent.
- The heightened IEG expression suggests that fish may experience fear or a similar emotional response to mirror images.
- This indicates a cognitive distinction, where fish recognize the unusual nature of the mirror image, despite not achieving self-recognition.
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