||In dioecious species, successful finding and mating with a partner is crucial for species survival. Complicated strategies are involved to ensure reproductive success. Sex pheromones have been commonly used to attract the opposite sex for mating, especially for insects. In the nematode worm Caenorhabditis remanei (C. remanei), females produce sex pheromones while Caenorhabditis elegans (C. elegans) males can be attracted by them. C. elegans, as a well-established model organism, has been used for studying the components for sex pheromone perception. CEMs, the only male-specific neuron in the head, have been identified to be required in sex pheromone perception, but their function and connection are poorly understood. My project focuses on the identification and characterization of the connectivity, sensory function and potential components of the male-specific neuron CEM, which define its identity in sex pheromone sensation and perception. In order to define the functional connectivity of CEMs in the sex pheromone perception pathway, I have recorded the physiological response of CEMs and AWAs upon different stimulations by using a genetically encoded fluorescent calcium indicator, GCaMP2. It is known that CEMs and AWAs are neurons required in sex pheromone perception. The excitation of either neuron by an optogenetic reagent, channelrhodopsin-2 (ChR2), could induce the activation of the other. This implies bi-directional communication between CEMs and AWAs, even when the physical connectivity remains unclear. It is also demonstrated that CEMs can respond to sex pheromones with or without exposure of AWAs to the environment. To identify the components which define the function of CEMs, I have initiated a project that compares the transcriptome of functional CEMs with non-functional CEMs in C. elegans ced-4 mutant hermaphrodites. The uniquely expressed and highly enriched components in the functional CEMs would only then be revealed and analyzed.