Todd Oakley's (TO) lab will focus on genomics, gene expression, and behavior of bivalve mollusks (Modiolus in shallows compared to Bathymodiolus from vents). TO will study Modiolus mussels, which are the closest shallow-water relatives to deep sea Bathymodiolus. Modiolus modiolus and M. capax are native to habitats bordering UC Santa Barbara and are accessible for comparative behavioral/physiological characterizations, which will be directly compared to equivalent data from B. azoricus collected by KTR and MM.  To record in situ activities of Modiolus, TO will deploy environmental sensors (temperature, light, pH, flow - with MM) and low-light/IR cameras in custom waterproof housings across multiple tidal cycles. TO will also deploy similar cameras and light meters at deep sea vents with access provided by MM to measure bioluminescence, which could indicate community wide rhythmicity that could serve as a biotic cue to entrain vent rhythms. TO with OP will quantify activity from image/video analyses and test for rhythmicity (KTR/OP). To study molecular evolution of candidate genes (e.g. opsin, Clock, Cry1, ARNT, ROR/HR3, aaNAT) and facilitate gene expression studies, TO will extract high molecular weight DNA for genome sequencing (size ~1.6 Gb for Modiolus) and compare assemblies from Falcon, hifiasm, and HiCanu. TO will also extract RNA from mantle tissue of five individual animals from wild Modiolus from five time points in each tidal cycle, replicated across 4 tidal cycles (5x5x4= 100 RNA preps) and use tag-seq to quantify global gene expression with bioinformatics support from KTR. Previously published molecular data from other research groups are available to facilitate comparative work [e.g. transcriptomes of B. azoricus, B. manusensis, B. platifrons, M. modiolus, and M. kurilensis) {Mat, 2020 #6926}{Jie, 2018 #7113} and a genome of B. platifrons {Sun, 2017 #7112}. Furthermore, although unstudied in Modiolus, tidal rhythms of more distant relatives of vent Bathymodiolus are well-studied, including Mytilus and Crassostrea, allowing new data from Modiolus to be incorporated into a broader comparative framework using phylogenetic models of character evolution. TO will identify candidate genes in Modiolus for sensors and clock oscillators with KTR, identify genes with tidally rhythmic expression with KTR, and quantify ratios of synonymous to non-synonymous substitutions that would indicate positive or purifying selection, or suggest neutral evolution. TO will compile data on rhythmic behaviors and for phylogenetic comparative analyses to understand the evolutionary history of rhythmicity in the two target groups. Finally, TO will search for e-box elements in genomic regions of candidate genes, which serve as enhancers that drive rhythmic gene expression. With KTR, we can test these regions as drivers of rhythmicity using in vitro luciferase assays.