What do fish make of mirror images?

Fish act aggressively towards their mirror image suggesting that they consider it another individual, whereas in some mammals behavioural response to mirrors may be an evidence of self-recognition. Since fish cannot self-recognize, we asked whether they could distinguish between fighting a mirror image and fighting a real fish. We compared molecular, physiological and behavioural responses in each condition and found large differences in brain gene expression levels. Although neither levels of aggressive behaviour nor circulating androgens differed between these conditions, males fighting a mirror image had higher immediate early gene (IEG) expression in brain areas homologous to the amygdala and hippocampus than controls. Since amygdalar responses are associated with fear and fear conditioning in other species, higher levels of brain activation when fighting a mirror suggest fish experience fear in response to fights with a mirror image. Clearly, the fish recognize something unusual about the mirror image and the differential brain response may reflect a cognitive distinction.

[1]  M. Lewis,et al.  Mirror-Image Stimulation and Self Recognition in Infancy. , 1975 .

[2]  J. M. Smith,et al.  The Logic of Animal Conflict , 1973, Nature.

[3]  Joseph E LeDoux,et al.  Fear conditioning induces associative long-term potentiation in the amygdala , 1997, Nature.

[4]  M. Dragunow,et al.  Kindling stimulation induces c-fos protein(s) in granule cells of the rat dentate gyrus , 1987, Nature.

[5]  R. Fernald,et al.  Cytoarchitecture of a Cichlid Fish Telencephalon , 2009, Brain, Behavior and Evolution.

[6]  E. Ross.  The Organization of Will , 1916, American Journal of Sociology.

[7]  William Rowan,et al.  The Study of Instinct , 1953 .

[8]  E. Jarvis,et al.  Rapid Behavioral and Genomic Responses to Social Opportunity , 2005, PLoS biology.

[9]  C. H. Summers,et al.  Monoaminergic activities of limbic regions are elevated during aggression: Influence of sympathetic social signaling , 2000, Brain Research.

[10]  R. Fernald,et al.  Androgen level and male social status in the African cichlid, Astatotilapia burtoni , 2006, Behavioural Brain Research.

[11]  Sheng Zhao,et al.  Comprehensive Algorithm for Quantitative Real-Time Polymerase Chain Reaction , 2005, J. Comput. Biol..

[12]  F. Rodríguez,et al.  Cognitive and emotional functions of the teleost fish cerebellum , 2005, Brain Research Bulletin.

[13]  C Salas,et al.  The effects of telencephalic pallial lesions on spatial, temporal, and emotional learning in goldfish , 2002, Brain Research Bulletin.

[14]  D. Alkon,et al.  Memory-specific temporal profiles of gene expression in the hippocampus , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[15]  H. Phillips,et al.  Hippocampal dysfunction and behavioral deficit in the water maze in mice: An unresolved issue? , 2002, Brain Research Bulletin.

[16]  N. Tinbergen,et al.  The Study of Instinct , 1953 .

[17]  T. Shike,et al.  Animal models. , 2001, Contributions to nephrology.

[18]  R. Morris,et al.  Distinct components of spatial learning revealed by prior training and NMDA receptor blockade , 1995, Nature.

[19]  H. Lissmann.  Die Umwelt des Kampffisches (Betta splendens Regan) , 1932, Zeitschrift für vergleichende Physiologie.

[20]  T. Curran,et al.  Review : The Immediate-Early Gene Response and Neuronal Death and Regeneration , 1995 .

[21]  Russell D. Fernald,et al.  Quantitative behavioural observations of Haplochromis burtoni under semi-natural conditions , 1977, Animal Behaviour.

[22]  R. Northcutt.  Connections of the lateral and medial divisions of the goldfish telencephalic pallium , 2006, The Journal of comparative neurology.

[23]  R. Fernald,et al.  Social regulation of the brain-pituitary-gonadal axis. , 1993, Proceedings of the National Academy of Sciences of the United States of America.

[24]  R. Fernald,et al.  The organization of the diencephalon and the pretectum in the cichlid fish, Haplochromis burtoni , 1985, The Journal of comparative neurology.

[25]  Bruce S. McEwen,et al.  INDUCTION OF CORTICOTROPIN-RELEASING HORMONE GENE EXPRESSION BY GLUCOCORTICOIDS: IMPLICATION FOR UNDERSTANDING THE STATES OF FEAR AND ANXIETY AND ALLOSTATIC LOAD , 1998, Psychoneuroendocrinology.

[26]  F. Rodríguez,et al.  Spatial memory and hippocampal pallium through vertebrate evolution: insights from reptiles and teleost fish , 2002, Brain Research Bulletin.

[27]  G. Gallup,et al.  Self-recognition in nonhuman primates: Past and future challenges. , 1999 .

[28]  R. Northcutt,et al.  An immunohistochemical study of the telencephalon of the senegal bichir (Polypterus senegalus) , 1992, The Journal of comparative neurology.

[29]  D. Clayton,et al.  The Genomic Action Potential , 2000, Neurobiology of Learning and Memory.