UC Davis

Previous research has shown that African jewel fish (Hemichromis bimaculatus) recognize pair-bonded mates during theirexchanges of egg-guarding duties. The current research examined the perceptual cues for face recognition by comparingtwo face models displaying anatomically realistic arrangements of blue iridophores derived from discriminant functionanalysis of distinct sibling groups. Four groups each consisting of 9 subadults were examined using a narrow compartmentrestraining lateral movement where face models were presented at eye level for eight trials. Because respiratory movementof the operculum can mechanically displace the eye thereby shifting the retinal image, jewel fish reduce their respirationrate during increased attention. When two experimental groups were presented with the same face models on four trials followinginitial model presentations, both groups exhibited stable respiration rates indicative of model habituation. When thehabituated face models were switched to novel face models on the fifth trial, the rates of respiration decreased as measuredby reliable increases in the elapsed times of opercular beats. Switching the models back to the habituated models on thesixth trial caused reliable decreases in the elapsed times of opercular beats, resembling the earlier trials for the habituatedmodels. Switching the face models again to the formerly novel models on the seventh trial produced respiration rates thatresembled those of the habituated models. The two control groups viewing the same models for all eight trials exhibited nosubstantial change in respiration rates. Together, these findings indicate that jewel fish can learn to recognize novel facesdisplaying unique arrangements of iridorphores after one trial of exposure.