Animals encounter information from different resources simultaneously, integrating input from multiple sensory systems before responding behaviorally. When different cues interact with one another, they may enhance, diminish, or have no impact on their responses. In this project, we test how the presence of chemical cues affect the perception of visual cues. Zebrafish (Danio rerio) often use both chemical cues and visual cues to communicate with shoal mates, to assess predation risk, and to locate food. For example, zebrafish rely on both olfactory cues and visual cues for kin recognition, and they frequently use both chemical and visual cues to search for and to capture prey. In zebrafish, the terminal nerve (TN) constitutes the olfacto-visual centrifugal pathway and connects the olfactory bulb with the retina, thus allowing olfactory perception also to activate visual receptors. Past studies have found that the presence of an olfactory cue can modulate visual sensitivity in zebrafish through the terminal nerve pathway. Alternatively, given that zebrafish are highly social, the presence of social chemical cues may distract individuals from responding to other visual cues, such as food and predator visual cues. Foraging and predator chemical cues, including chemical food cues and alarm cues, may also distract individuals from responding to non-essential visual cues. Here, we test whether the response to a visual cue either increases or decreases when presented in concert with alanine, an amino acid that represents the olfactory cues of zebrafish prey. We found that the presence of chemical cues did not affect whether zebrafish responded to visual cues, but that the fish took longer to respond to visual cues when chemical cues were also present. These findings suggest that different aspects of behavior could be affected by the interaction between sensory modalities. We also found that this impact of delayed response was significant only when the visual cue<br/>was weak compared to the strength of the chemical cue, suggesting that the salience of interacting cues may also have an influence on determining the outcomes of the interactions. Overall, the interactive effects of chemicals on an animal’s response to visual cues may also have wide-ranging impacts on behavior including foraging, mating, and evading predators, and the interaction of cues may affect different aspects of the same behavior.

Skulls house sensory systems that perceive communicative signals and may be shaped by behavior over evolutionary time. Here, I used an indicator trait (presence of a blue patch used as a sexual signal and linked to differences in sensory behavior) to test whether Sceloporus lizard species that rely more on olfactory behavior differ in skull morphology and sensory structures from those that rely more on visual behavior. We marked specific morphological points on Sceloporus skulls to compare the distances between significant sensory structures, such as eye orbit and snout length. Adjusting for body length, I found that white-bellied lizards have a wider snout tip, suggesting more evolutionary investment in chemosensory structures. White-bellied lizards also had a pattern of larger olfactory and visual skull morphology. Finally, I found a strong robust positive correlation between visual and olfactory structures. Together, our results support a hypothesis of strong integration between sensory structures, suggesting that vision and olfaction are evolving in concert rather than independently in Sceloporus lizards.