SPECTRAL SENSITIVITY OF THE INVASIVE LIONFISH (PTEROIS SPECIES) RETINA AND ITS CAPACITY FOR CHANGE IN RESPONSE TO LIGHTING CONDITION
Carroll, Miranda Roseland
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Since their first confirmed sighting in 1985 in the tropical western Atlantic, invasive lionfish of the genus Pterois have had a detrimental impact on marine systems in this region, including significant declines in native reef-fish populations. The environmental tolerances of these predators are very broad, allowing them to inhabit a variety of environments: they can withstand large ranges of depths, salinities, and temperatures. Understanding their physiological and behavioral characteristics can provide insight for the success of these invaders. Adaptable visual capabilities is one biological characteristic that may assist their invasive success. I hypothesized that lionfish possess retinal plasticity and can adapt their spectral sensitivity in response to lighting conditions most prevalent in an invaded region, thus making them more effective predators. Lionfish were collected alive along the East coast of Florida. To assess the adaptability of their visual systems, fish were housed for four months under either blue or red lighting conditions on a 12-hour-light/12-hour-dark cycle. Electroretinography was used to assess the spectral sensitivity profile by measuring the initial retinal response of the fish to different wavelengths of light, from 350 to 650 nm in 50-nm increments, and again after two and four months under the experimental lighting conditions. Regardless of the lighting regime, lionfish were most sensitive to the green (500 – 550 nm) region of the spectrum, and very weakly sensitive to the red (600 – 650 nm) region of the spectrum. Neither lighting condition nor time of exposure had a significant influence on spectral sensitivity (2- Way Repeated Measures ANCOVA and Anderson-Darling k-sample test). This lack of plasticity of spectral sensitivity may be due to the primarily crepuscular feeding habits of the species. Feeding under twilight and rapidly changing light conditions makes it more likely that their retinas are primarily adapted to photon capture in low light conditions, rendering color vision less essential. Further examination and characterization of the lionfish visual system is thus warranted to determine how lionfish use vision under changing and low light conditions. Such studies may help understand the biological traits that enable the success of this invader and help define additional habitats that are vulnerable to invasion.