Population outbreaks of the coral-eating crown-of-thorns starfish (CoTS) have resulted in extensive coral mortality on reefs in the Indo-Pacific region and is considered one of the major contributors of significant declines in coral cover in Australia’s Great Barrier Reef (GBR). Effective management of CoTS outbreaks rely on improved understanding of the drivers of individual and population-level differences in reproductive patterns, particularly those factors that may contribute to step-changes in reproductive success, such as the timing and synchronicity of spawning. This study investigated gametogenesis and spawning patterns in a persistent population of CoTS at one reef within the putative initiation zone where outbreaks appear to start in the GBR. We examined variation in the progression of gametogenesis and spawning patterns over two distinct spawning seasons (2013–2014, 2014–2015), using a variety of methods: macroscopic examination of gonads, assessment of monthly changes in the gonadosomatic index, analysis of histological sections of ovaries and testes, and comparison of the size-frequency distribution of oocytes. These methods yielded consistent results, which revealed striking variation in the timing of maturation and gamete release between two summer spawning seasons, possibly depending on local environmental conditions. The optimal temperature for gametogenesis and spawning occurred when seawater temperature exceeded 28 ℃. Gradual increases in temperature (to > 28 ℃) over spawning months in 2013–2014 caused ‘batch/dribble’ spawning, while abrupt increases in temperature in 2014–2015 caused synchronous ‘all-at-once’ spawning. During more rapid warming events in the typical summer spawning period, CoTS may exhibit greater synchronicity in their reproductive capacity, which may help seed outbreaks. This work advances our understanding of the mechanisms surrounding periodic fluctuations in CoTS densities and improves predictions on how this corallivorous predator will respond to environmental perturbations due to climate change.

中文翻译：

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大堡礁北部爆发起始区内棘冠海星配子发生和产卵模式的时间变化

吃珊瑚的棘冠海星（CoTS）的种群爆发导致印度-太平洋地区珊瑚礁上的珊瑚大量死亡，被认为是澳大利亚大堡礁珊瑚覆盖率显着下降的主要原因之一。英镑）。CoTS 爆发的有效管理依赖于对繁殖模式中个体和种群水平差异的驱动因素的更好理解，特别是那些可能导致繁殖成功的阶跃变化的因素，例如产卵的时间和同步性。这项研究调查了在 GBR 爆发似乎开始的推定起始区内的一个珊瑚礁上的 CoTS 持久种群的配子发生和产卵模式。我们使用多种方法检查了两个不同产卵季节（2013-2014、2014-2015）中配子发生和产卵模式的进展变化：性腺宏观检查、性腺指数每月变化评估、组织切片分析卵巢和睾丸，以及卵母细胞大小频率分布的比较。这些方法产生了一致的结果，揭示了两个夏季产卵季节之间成熟时间和配子释放的显着变化，这可能取决于当地的环境条件。配子发生和产卵的最适温度出现在海水温度超过28 ℃时。2013-2014 年产卵月份温度逐渐升高（至 > 28 ℃）导致“分批/滴状”产卵，而 2014-2015 年温度的突然升高导致了同步的“一次性”产卵。在典型的夏季产卵期更快速的变暖事件中，CoTS 的繁殖能力可能表现出更大的同步性，这可能有助于种子爆发。这项工作增进了我们对 CoTS 密度周期性波动机制的理解，并改进了对这种食珊瑚捕食者如何应对气候变化引起的环境扰动的预测。