Polarized light in communication and behavior of two fish species APPROVED BY SUPERVISING COMMITTEE:

Many animals can see polarization of light (a property to which humans are visually insensitive) and use polarization for a variety of behavioral tasks such as navigation and foraging. The polarized light environment is spatially and temporally complex, presenting a unique challenge for signaling or crypsis in animals with polarization vision. Some invertebrates have polarization body patterning that may be used in communication, but only in one species has polarization body patterning been shown to affect receiver behavior, and polarization communication has never been investigated in vertebrates. Many species of fish see polarized light and the aquatic environment is highly polarized; body patterning in visual communication is also common in fish. We measured polarization patterning in the northern swordtail (Xiphophorus nigrensis) and used behavioral assays to measure response to polarization cues of social stimuli in the swordtail and in the rockhind (Epinephelus adscensionis). We found that swordtails have sexually dimorphic polarization patterning. By manipulating the light environment of stimulus males in a two-choice female preference test, we presented females a highly-polarized male and a male with reduced polarization patterning. Females preferred the polarized male, indicating that polarization patterning