Coral reproduction is vital to the persistence of coral reefs. Decades of ecological studies have correlated environmental variables, such as temperature and light, to the timing of reproduction in anthozoan cnidarians, including corals and sea anemones. However, elevated temperatures associated with climate change impair reproductive success and threaten the resilience of coral reefs globally. Empirically evaluating the effect of the key environmental variables temperature and light on the timing of reproduction, at ecological and molecular levels, will further our understanding of the impacts of a changing environment on the future of coral reproductive success. At the transcriptomic level, the signaling pathways and mechanisms involved in transducing environmental cues into molecular signals and coordinating reproductive events is poorly understood. The few studies examining molecular events associated with reproduction have focused on spawning corals: no study has examined these events in a brooding coral.
Cnidarians are both evolutionarily and ecologically significant. As early-diverging basal metazoans, they occupy a key position as the sister-taxon to bilaterians, and are the foundational species of coral reef ecosystems. Therefore, hypothesis-generating studies aiming to characterize both novel and homologous genes involved in coordinating reproductive events can provide a basis for detailing the genetic and physiological mechanisms governing reproduction in ancestral animal systems.
In this work, Chapters 2 and 3 investigate the impacts of elevated temperature on reproductive timing in the coral Pocillopora damicornis and integrate ecological and genomic methods to describe environmental and physiological components of reproductive timing in a brooding coral. My findings reveal that there is plasticity in the timing of reproduction at both an ecological and transcriptomic level, as elevated temperature results in earlier larval release and a disruption of transcriptomic profiles associated with the timing of reproduction. Chapter 4 explores the potential of the sea anemone developmental model, Nematostella vectensis as a reproductive model for corals and examines gene expression patterns associated with light + temperature-induced spawning. I describe smaller transcriptomic changes during reproduction, compared to brooding and spawning corals, and suggest that reproductive priming and post-translational regulation leads to modest transcriptional change. Overall, this work describes the impacts of elevated temperature on reproductive timing in a brooding coral and provides a detailed comparison of the transcriptomic mechanisms associated with light + temperature induced reproduction both in a brooding coral in nature and a laboratory-maintained sea anemone.