Date of Award
Program or Major
Molecular and Evolutionary Systems Biology
Doctor of Philosophy
W. Kelley Thomas
Class Hydrozoa belongs to Phylum Cnidaria which occupies a key phylogenetic position in animal evolution. Phylum Cnidaria, which includes animals such as jellyfish, sea anemones, corals, and hydrozoans, is the evolutionary sister lineage to bilaterians. My Ph.D. research is focused on understanding how hydrozoans integrate sensory information from the environment at the genetic level and how that mediates an organismal behavioral response by investigating three closely related hydrozoan species: Hydractinia symbiolongicarpus, Hydra vulgaris, and Ectopleura crocea. Many of the studies on cnidarian sensory ecology have focused on adult stages or anthozoan species (sea anemones and corals) leaving a lack of understanding of Hydrozoan sensory systems, especially at the larval stage. Additionally, most studies of Hydrozoan sensory ecology have focused on chemosensory and mechanosensory integration leaving many questions opened about hydrozoan photosensitivity. My Ph.D. research aims to address these open questions and questions regarding the evolution of sensory systems and the sensory ecology of Hydrozoans. My first chapter is a literature review of photosensory systems in Cnidaria which provides a comprehensive overview of what we know about photosensitivity in the phylum. My second chapter investigates the genetic components involved in the phototactic response in the planula larva of the model hydrozoan, Hydractinia symbiolongicarpus. This chapter aims to deepen our understanding of how larvae in Hydrozoa utilize photosensory information and the genetic basis behind the photoresponse. Here, I combined a developmental transcriptome study with behavioral work conducted by a previous graduate student and found that Hydractinia planulae larvae are sensitive to blue and green wavelengths of light and express sensory genes indicative of opsin-mediated phototransduction prior to competency. My third chapter investigates key components involved in the phototransduction pathway in another model hydrozoan, Hydra vulgaris. Important questions remain about the composition and function of the cnidarian pathway which is the focus of this chapter. Here, I have combined studies of gene phylogeny, comparative transcriptomics, and RNA fluorescent in situ hybridizations (FISH) with behavioral work from a previous graduate student to demonstrate components involved in the photosensory pathway of Hydra. We identified that cnidarian phototransduction uses both Adenylate Cyclase and phosphodiesterase to coordinate photobehavior. Lastly, my fourth chapter investigates sensory integration during larval settlement in a key fouling hydrozoan, Ectopleura crocea. This study aimed to identify the sensory cues being utilized in the settlement decision and the underlying genetic machinery. Here, I combined a settlement study, a developmental transcriptome study, immunohistochemistry, and RNA FISH staining to investigate sensory integration of the E. crocea actinula larva. We found that actinulae are utilizing multisensory integration (MSI) which manifested as a sensory cue hierarchy. Additionally, we also identified candidate sensory genes and have uncovered preliminary evidence that polymodality may underly MSI in actinulae larvae. Altogether, this research provides a better understanding of sensory integration in hydrozoans and provides insights into the evolution of sensory systems.
Birch, Sydney, "Integrating behavior and genomics to understand sensory integration in Cnidarians" (2022). Doctoral Dissertations. 2663.