Seminar: Dr. Ching-Fong Chang

Distinguished Professor, Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung, Taiwan

Title: Coral Reproduction and Evolutionary Adaptation in the Face of Climate Change

Abstract: We investigated the reproduction and reproductive hormones in scleractinian corals (Fimbriaphyllia ancora, Tubastraea aurea). Transcriptome, genome, and methylome approaches are applied. The sexual system, reproductive mode, seasonality and the regulation of reproduction were investigated. The sexual function can be classified into two main categories: gonochoric and hermaphroditic. In fish, the majority are gonochoristic fish, about 1.5% of fish species are hermaphroditic. In contrast, most coral species are hermaphroditic spawners and brooders (> 80%). In addition to external factors (temperature, photoperiod, tides, and others), the intrinsic factors such as hormones may also regulate the coral germ cell growth, maturation, and spawning. We found sex steroids-like, aromatase activity, and irGnRH-like compounds were all increased to a peak during reproductive season in F. ancora coral. Some important factors such as steroidogenic pathway and vitellogenic gene were also found in the gonad, and vitellogenin expression was correlated to the oocyte growth. Full sequences of Gly-Leu-Try-amide (GLWamide) and Glu-Gly-Arg-Phe-amide (RFamide) neuropeptide precursors were obtained. These neuropeptides could induce tentacle contraction which may be related to coral behaviors including reproduction, feeding, stress, or others. The hormonal regulation for the coral reproduction is under further investigation. We further applied a species of coral Tubastraea aurea which could survive and adapt in the hydrothermal vent ecosystem (with high acidic, sulfide, and hypoxia) in the water zone around Kueishan Island, northeastern Taiwan for studying adaptive responses to environmental stress and climate change. Vent corals had higher transient receptor potential ion channels (TRPs) transcripts, anti-ROS (reactive oxygen species; i.e., superoxide dismutase) enzyme activities, and 5-methylcytosine levels (5-mC, a DNA methylation product) than non-vent corals. These increases may be related to the evolutionary adaptation of vent corals in hydrothermal vent extreme environments. We further found that hydrothermal vent coral T. aurea had a stronger performance of sexual (gametogenic activity) and asexual (budding activity) reproduction compared to non-vent control corals. Our studies suggest that intrinsic mechanisms have evolved in corals for the successful sexual and asexual reproduction in the face of environmental variability and extreme environments. The evolutionary and adaptive ecophysiology in corals related to genome methylation is under further exploration.