Visual and Chemosensory Guidance of Predatory Behavior in the California Two-Spot Octopus (Octopus bimaculoides) Dana Callahan Biology Department & Program In Neuroscience. Middlebury College. Middlebury Vermont We assessed the effects of vision and chemosensation on predatory behavior in Octopus bimaculoides.. Octopuses underwent three trials: visual stimulus only, chemical stimulus only, and visuochemical stimulus. The behavioral paradigm required octopuses to attack live prey in a clear glass tube. Predatory behaviors were quantified, and results were compared across trials. Data collection for the first 5 subjects was completed on 4/16/13, and the next 6 subjects are arriving for testing on 4/17/13. For this reason, the observations presented below are based on preliminary qualitative observations of trials. Preliminary observations suggest that the chemical stimulus alone decreased latency to attack, relative to the visual stimulus alone or the visuochemical stimulus. Preliminary observations suggest that the chemical stimulus may have increased total time spent in contact with the stimulus, suggesting that chemosensation increased perseverance in predation. Interindividual variation in basal activity level, curiosity, and prey preference may have confounded our results, as suggested by previous studies (Ambrose 1982; Byrne et al., 2001). Preliminary comparisons across trials suggest that the order in which octopuses underwent the three trials did not significantly affect predatory behavior. This suggests that learning and/or desensitization to the stimulus did not occur. Vision is primary sensory trigger for predatory behavior. Chemical stimuli are significantly less effective than visual stimuli at inducing predatory behavior., but chemical stimuli may increase predatory perseverance (e.g. frequency of attacks and time spent in contact with the stimulus). This research is still underway, and we hope to strengthen our findings as we collect data on the next group of animals. Further development of this study warrants examination of the effects of a variety of chemical stimuli on predatory behavior. Octopuses (Phylum Mollusca, Class Cephalopoda) are proven models for the neurobiology of behavior (Messenger, 1998). However, neurobiologists have not achieved a complete understanding of sensory processing in the octopus (D’Aniello et al., 2005; D’Este et al., 2008). While recent studies have demonstrated visual guidance of behavior (Byrne et al., 2001; Fiorito et al., 2005) and chemosensory abilities in cephalopods(Lee, 1992; Darmaillacq et al., 2004; Fry, 2011), the biological relevance of these sensory capabilities continues to be examined. Octopuses are active predators, preying on fish, crustaceans (e.g. shrimps, crabs), and mollusks (Ambrose, 1982; Byrne et al., 2001). Octopus predatory behavior varies among individuals and depends on prey type (Dickel et al., 2001; Cartron et al., 2013). Such complex predatory behavior requires highly effective sensorimotor integration. Octopuses use vision to guide their initial approach to prey (Young, 1965). In addition, findings that octopuses demonstrate positive chemotaxis to chemical stimuli related to prey (Lee, 1992; Fry, 2011) suggest that predatory behavior may also be influenced by chemosensation. The present study seeks to clarify the ecological relevance of octopus chemosensation by studying how vision and chemosensation interact to guide predatory behavior in the California two-spot octopus (Octopus bimaculoides). We presented octopuses with visual stimuli, chemical stimuli, or visuochemical stimuli and quantified the resulting predatory behaviors. Based on previous research, we hypothesized that vision would be the primary initiator of predatory behavior, but that the effects of vision and chemosensation on predatory behavior would be additive. In other words, we hypothesized that predatory behavior would be stimulated most strongly by visual and chemical cues