SGER: UV Communication in Swordtails

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Many animals experience parts of the environment to which we are not privy. Bats use echolocation, some insects sense substrate vibrations. We recently found that a fish, the pygmy swordtail, communicates in the ultraviolet (UV)-- light to which our skin but not ours eyes are sensitive. Male swordtails have a sword that extends beyond the tail fin. Our previous studies, which inadvertently excluded UV, were never able to show that females preferred males with swords to those without swords. Recently we discovered that the sword reflects UV, and that when tested under light containing UV (e.g. sunlight) females do indeed prefer males with swords. Thus UV plays a critical role in the communication system involved in mate choice. We also found that the swordtail's major predator, the Mexican tetra, does not see in the UV. Thus males can increase their conspicuousness to females but not predators by adding UV reflectance to the sword.In the proposed study we will determine how general the UV communication system is in these types of fishes, if variation in the presence of UV influence when the animal's court, how sensitive the visual system is to UV, if the presence of UV does not influence the predator's hunting success, and if the swordtails use UV for other tasks, such as locating their own prey. These studies promise to give us insights into a sensory world of these animals that was previously unknown.