Illuminating Dinoflagellates: Integrating Technology for Movement and Light Sensing

Abstract

Movement is a fundamental feature of life that shapes ecological dynamics. This dissertation advances the study of movement behavior in dinoflagellates, a diverse group of algal protists best known for forming harmful algal blooms. Understanding their movement capacities, drivers, and mechanisms is essential for improving ecological modeling, developing accurate sampling methodologies, monitoring proliferation and colonization, and uncovering the traits that have sustained the dinoflagellate lineage for millennia.To expand behavioral research in this group, open-source imaging hardware and software were developed to enable accessible, reproducible studies across different experimental contexts. Using various types of microscopic imaging techniques, including multiple solutions developed as part of this dissertation, the movement of 13 strains from six Gambierdiscus species was characterized, revealing species-specific activity rhythms, and distinct diel movement patterns. Experiments with modified lighting conditions and schedules revealed endogenous circadian rhythms that regulate this movement, as well as what appears to be three different oscillator systems and entrainment systems in as many species. These point to the movement of Gambierdiscus being a key part of its ecology and life strategy, although the underlying mechanisms and reasons remain enigmatic. In exploring links between gene and function in dinoflagellates, the rhodopsin repertoires of A. carterae and K. veneficum, two species with well developed genomic or transcriptomic resources, were characterized. Only two canonical rhodopsins were identified from the transcriptomes out of 28 total putative rhodopsins, including the first discovery of a heliorhodopsin in dinoflagellates, found in K. veneficum. No canonical ion-pumping or phototactic capacity was found in A. carterae, whereas these were retained in K. veneficum. Both species also exhibited a preponderance of chimeric gene fusions of the rhodopsin backbone with novel accessory domains, indicating functional diversification of originally ion-pumping rhodopsins into yet undescribed light-gated functions. Taken together, the work collected in this dissertation enables faster, more efficient behavioral and bioinformatic studies into the group, as well as illuminates new aspects of dinoflagellate biology while revealing just how much of their complexity remains hidden, underscoring the remarkable evolutionary divergence that makes these tiny algal cells fascinating.