Timing of Larval Release by Five Coral Species in Southern Taiwan：Seasonality, Lunar and Diurnal Periodicity

• Main Authors: Ke-han Lin, 林科含
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/02614385845827855620

碩士 === 國立中山大學 === 海洋生物研究所 === 93 === The seasonality, lunar and diurnal periodicity of planulation of five scleractinian corals, Seriatopora hystrix, Stylophora pistillata, Pocillopora damicornis, Euphyllia glabrescens and Tubastraea aurea, were compared. Corals were collected monthly and maintained in outdoor, flow-through systems to quantify the number of larvae released. Planulation of the five species occurred throughout the year. The long period of reproduction may be related to the warm mean seawater temperature in Nanwan Bay. S. pistillata released few larvae during late summer and early fall, suggesting the seasonality of reproduction. The pattern of lunar cycle can be classified into three strategies: (1) Planulation of S. hystrix and P. damicornis showed clear lunar periodicity and the peak of larval release shifted with different months. The peak of planulation occurred around the full moon in winter then shifted gradually to the first quarter moon phase in summer. The phase shift of larval release may be related to the seasonal variation of seawater temperature and the sudden temperature drops caused by upwelling. (2) Planulation of S. pistillata showed clear lunar periodicity and the peak of larval release occurred around the full moon. This may promote the larval dispersal. (3) E. glabrescens and T. aurea showed clearly lunar periodicity and the peak of larval release changed with different months. The peak of planulation shifted from full moon to new moon during winter and spring while it shifted from new moon to full moon during summer and fall. The pattern of diurnal cycle also can be classified into three strategies: (1) Planulation of S. hystrix and S. pistillata revealed a well-defined diurnal pattern with most planulae being released close to sunrise. (2) P. damicornis and E. glabrescens released larvae throughout the day, with two peaks occurring in the early morning and in the night. Corals of all three pocilloporids and E. glabrescens timed larvae release relative to the light-dark cycle suggesting that diurnal cycle determined when larvae were released. Larvae released in the dark may have lower risk of predation effect. Furthermore, the peak planulation occurred close to sunrise may be advantageous for some mature larvae to have light cues for quick settlement within the natal reef. (3) The azooxanthellate coral T. aurea released larvae throughout the day with no apparent cycle. These results suggest that zooxanthellae may play a role in regulating the diurnal cycle.