Effects of thermal stress on fertilization and early embryogenesis in coral species from the Great Barrier Reef and Japan

Favites chinensis colonies were collected from the reef flat off Sesoko Island, Okinawa and transported to aquaria at Sesoko Station. After spawning, sperm and eggs were separated and then used in fertilization experiments at 7 temperatures (25.5, 26.4, 27.0, 27.8, 28.9, 30.2 and 31.6°C). Early fertilization (first and second cleavage) was assessed after 3 hours using a dissecting microscope.Acropora millepora were collected from Davies Reef on the Great Barrier Reef and transported to aquaria at the Australian Institute of Marine Science. Similar fertilization experiments were carried out at 28.3, 30.4, 31.8, 32.8 and 34.1°C. Embryos were sampled at 2 and 4 hours, fixed in Bouins solution and later assessed for fertilization success and gamete quality.Acropora millepora, Favites abdita and Mycedium elephantotus, were collected from Davies Reef. In this experiment, eggs and sperm were separately pre-exposed to temperatures of 26, 28, 30 and 32°C for 30 minutes prior to fertilization at these tempertures. The embryos were sampled and fixed at 2 and 4 hours and assessed for fertilization success, abnormal embryo development and cell cleavage rates. This research was undertaken to examine the influence of seawater temperature on fertilization success and early embryogenesis of reef-building corals, in different families, from the Great Barrier Reef and Japan. Gametes were subjected to temperatures ranging from 2°C below average temperatures during the spawning period at each location to 5-6°C above average, which encompasses the range of increases that might be expected under climate change scenarios.

中华扁脑珊瑚(Favites chinensis)的群体采集自冲绳(Okinawa)濑长岛(Sesoko Island)附近的礁坪，转运至濑古工作站(Sesoko Station)的水族箱内。产卵完成后，分离得到精子与卵子，随后在7个温度梯度（25.5、26.4、27.0、27.8、28.9、30.2及31.6℃）下开展受精实验。实验启动3小时后，利用解剖显微镜评估早期受精过程（第一次及第二次卵裂）。多孔鹿角珊瑚(Acropora millepora)采集自大堡礁(Great Barrier Reef)的戴维斯礁(Davies Reef)，转运至澳大利亚海洋科学研究所(Australian Institute of Marine Science)的水族箱中，同样在28.3、30.4、31.8、32.8及34.1℃的温度条件下开展了类似的受精实验。分别于实验开始后2小时和4小时采集胚胎，使用波恩固定液(Bouin's solution)固定，后续评估受精成功率与配子质量。另有采自大堡礁戴维斯礁的物种，包括多孔鹿角珊瑚(Acropora millepora)、隐扁脑珊瑚(Favites abdita)及象耳石珊瑚(Mycedium elephantotus)，在此实验中，将精子与卵子分别在26、28、30及32℃的环境中预暴露30分钟，随后在对应温度下开展受精实验。分别于2小时和4小时时采集并固定胚胎，评估受精成功率、胚胎异常发育情况及细胞卵裂速率。本研究旨在探究海水温度对采自大堡礁与日本的不同科造礁珊瑚(reef-building corals)受精成功率及早期胚胎发生的影响。实验所用配子的处理温度范围为各采样点产卵期平均温度下调2℃至平均温度上调5-6℃，该区间覆盖了气候变化情景(climate change scenarios)下预估可能出现的温度升高幅度。