溫度與縮小化對於南台灣維氏腦紋珊瑚有性生殖之影響

Influence of temperature and downsizing on the reproductive patterns of brain coral, Platygyra verweyi, (Scleractinia; Merulinidae) in southern Taiwan

曹景昕(Ching-Hsin Tsao)

指導教授 ： 陳昭倫

國立臺灣大學/理學院/海洋研究所/碩士(2016年)

https://doi.org/10.6342/NTU201603610

摘要

有性生殖是造礁珊瑚重要生活史階段之一。在排放型造礁珊瑚的有性生殖中，配子發育以及排放配子的時間最為影響之後卵的受精率或是幼體的存活率。然而，在氣候變遷與人為活動等逆境的影響下，這些有性生殖特徵可能受到不同程度的衝擊，進而影響珊瑚的生存與族群的繁衍。過去的研究指出海水溫升高的逆境直接影響珊瑚的生存。為了進ㄧ步了解海水溫度對於造礁珊瑚配子發育以及排放配子的時間之影響，我選定墾丁海域核能三廠出水口右側（以下稱出水口）與恆春半島西岸萬里桐海域維氏腦紋珊瑚(Platygyra verweyi)族群為對象，進行兩海域維氏腦紋珊瑚交互搬遷，並於2015年4月6月生殖季時檢查搬遷組、控制組與母族群珊瑚本體之卵大小、孕卵數以及產卵時間的差異。出水口海水年均溫與日溫差(30.5oC ~ 23.4oC ± 2.1~2.5 °C)都顯著高於萬里桐的年均溫與日溫差(29.7oC ~ 22.6oC ± 1.1~1.2°C)。由結果我們發現孕卵數與排卵時間會受到縮小化的影響。兩地控制組的孕卵數都少於母群體三分之一或是更少。在兩地比較上，萬里桐母群體與控制組孕卵數分別大於出水口母群體與控制組。兩地搬遷組的孕卵數都低於母群體與控制組，但是對互相並沒有顯著差異，推論是因為能量轉移至生長或是維持生理運作之結果，造成無法檢測溫度對於孕卵數的影響。在卵徑上，出水口母群體與控制組的卵徑明顯大於萬里桐母群體與控制組，且在搬遷組的卵徑上，由萬里桐搬至出水口的卵的卵徑增加且大於出水口搬至萬里桐的卵；反之，出水口搬至萬里桐的卵徑明顯縮小。在排卵時間上，出水口母群體早於萬里桐母群體約兩周。但是在兩地控制組都有相較於母群體提早產卵的現象發生。此外搬遷組的產卵時間跟其所在位置之母群體相似，而非同其原母群體。由本實驗可以發現，縮小化會造成孕卵數降低，且會提早排卵。此現象可能是能量重新轉移至生長或是維持其他生理象限，必須降低配子產量；而提早生產則可能是珊瑚必須加速度過配子生成的過程，進而繼續生長或是修復傷口。本論文亦證明海溫異常可影響卵徑與排卵時間，前者可能是在極端環境下母體對於其後代能量分配的改變之結果，後者則顯示海溫為珊瑚排卵之重要依據。

關鍵字

維氏腦紋珊瑚 ； 海溫異常 ； 縮小化 ； 配子生成 ； 排卵時間

並列摘要

Sexual reproduction is considered as a key factor for the maintenance of broadcast spawning scleractinian coral populations and genetic diversity. In the process of reproduction, gametogenesis pattern and spawning time are the two fundamental stages which do not only influence fertilization but also larval survival. However, suffering from increasing anthropogenic and climatic disturbances, gametogenesis pattern (fecundity and oocytes size) and spawning time of corals are highly influenced, this may lead to a reduction of fertilization success. In this study, we carried out reciprocal transplantation experiment to examine how coral gametogenesis pattern and spawning time change under hyper-thermal and highly variable environment conditions. Two sites in Kenting, Taiwan, with contrasting thermal environments: Outlet of the Nuclear Power Plant (OL) with higher daily mean temperature and daily temperature fluctuation (30.5°C ~ 23.4°C ± 2.1~2.5 °C), and Wanlitung (WLT) with a relatively stable temperature environment (29.7°C ~ 22.6°C ± 1.1~1.2°C), were chosen as the study sites. At each site, five colonies of coral Platygyra verweyi were sampled and separated into three group: maternal colonies, control group (making into nubbins) and transplantation group (making into nubbins and transplanting to another site). Results of fecundity were different from three groups and site. Downsizing and transplantation led to a great number of reduction in fecundity (1/3 or less oocytes per polyp) in the transplantation groups compared to maternal colonies in both sites. Furthermore, fecundity of samples from maternal and control groups in WLT were higher than those in OL, respectively. Fecundity of transplantation groups in both site was lower than maternal colonies and control groups but both transplantation groups were not different from each other. Unlike fecundity, oocyte size was larger in all groups in OL compared to WLT, respectively. However, downsizing had little but not significant impact on oocyte size. Spawning time of downsized nubbins were advanced in control groups in both sites. But spawning time of transplantation groups were the same as maternal colonies in the sites where they have been transplanted. In general, this study showed that downsizing has impacts on fecundity and spawning time which might because of energy re-allocation to growth or regeneration. Besides, temperature anomalies do have effects on oocyte size and spawning time, under extreme environment, corals tend to increase single offspring fitness and sharply define the spawning time in order to increase fertilization success.

並列關鍵字

Platygyra verweyi ； Temperature anomalies ； Downsizing ； Gametogenesis ； Spawning time

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