Exploring emotional contagion in zebrafish: A virtual-demonstrator study of positive and negative emotions.

Emotional contagion, the transmission of emotions within a group, has been extensively studied in mammals but remains largely unexplored in fish. This study aims to investigate whether emotional contagion, specifically in terms of low and high anxiety levels, can be evoked in zebrafish. This freshwater species has been gaining momentum due to its high genetic homology to humans and complex behavioral repertoire, making it well-suited for exploring social behavior. Our hypothesis posits that zebrafish have the ability to transmit positive and negative emotions to one another through visual cues only and that this transmission is robust over time. To test this, we employed a virtual demonstrator fish approach, where videos of zebrafish exhibiting either high or low geotactic behavior were shown to live zebrafish. Geotaxis, the tendency of a fish to spend more time at the bottom of the tank, is a sensitive measure of anxiety, with high geotactic behavior corresponding to high anxiety levels and vice versa. Our findings indicate that the virtual demonstrator successfully transmitted emotional states to the live fish, as evidenced by changes in the time spent at the bottom of the tank, linear acceleration, and fast-turning maneuvers, metrics that quantify anxiety-like behaviors such as geotaxis and erratic movements. Additionally, we conducted a causal analysis using a transfer entropy approach, revealing a significant flow of information from the virtual demonstrator fish to the live fish, indicating the efficacy and potential of this approach in studying emotional contagion. This study provides additional empirical evidence of how visual cues alone from a virtual demonstrator exhibiting high or low anxious behavior can elicit similar behavioral states in bystander fish, highlighting the potential for emotional contagion beyond mammalian and avian models.

Discovery of Phytophthora infestans genes expressed in planta through mining of cDNA libraries.

BACKGROUND: Phytophthora infestans (Mont.) de Bary causes late blight of potato and tomato, and has a broad host range within the Solanaceae family. Most studies of the Phytophthora--Solanum pathosystem have focused on gene expression in the host and have not analyzed pathogen gene expression in planta. METHODOLOGY/PRINCIPAL FINDINGS: We describe in detail an in silico approach to mine ESTs from inoculated host plants deposited in a database in order to identify particular pathogen sequences associated with disease. We identified candidate effector genes through mining of 22,795 ESTs corresponding to P. infestans cDNA libraries in compatible and incompatible interactions with hosts from the Solanaceae family. CONCLUSIONS/SIGNIFICANCE: We annotated genes of P. infestans expressed in planta associated with late blight using different approaches and assigned putative functions to 373 out of the 501 sequences found in the P. infestans genome draft, including putative secreted proteins, domains associated with pathogenicity and poorly characterized proteins ideal for further experimental studies. Our study provides a methodology for analyzing cDNA libraries and provides an understanding of the plant--oomycete pathosystems that is independent of the host, condition, or type of sample by identifying genes of the pathogen expressed in planta.