Sneak_early_dataset

In species with external fertilisation, sperm release by males is considered crucial for synchronizing with female egg release, yet little is known about sperm release strategies when females lay eggs over extended periods. In the intertidal goby Bathygobius fuscus, smaller males intrude into the nest during pair spawning, which lasts several hours, and release sperm. Here, we investigated how the timing of sneaking affects the paternity of sneaker males, using controlled aquarium experiments combined with genetic paternity analysis. Our results showed that early nest intrusion after the onset of egg-laying (within approximately 1 hour) significantly increased sneaker male paternity. This may be partly because early released sperm remain viable for several hours and can fertilise eggs laid later. Another possible mechanism is that females laid approximately 70% of their total eggs during the first hour of spawning. These findings suggest that early sneaking maximizes fertilization opportunities of sneaker males, likely as an adaptation to prolonged oviposition and long sperm longevity. This study proposes the importance of considering the timing and sequence of sperm release in understanding the consequences of sperm competition in externally fertilising species with a time gap between sperm release and fertilization, similar to that of species with internal fertilisation.对于体外受精（external fertilisation）物种而言，雄性释放精子以匹配雌性产卵节律被认为是至关重要的，但目前对于雌性长时间产卵场景下的精子释放策略仍鲜有研究。在潮间带虾虎鱼（Bathygobius fuscus）中，体型较小的偷配雄性（sneaker male）会在持续数小时的配对产卵期间侵入巢穴并释放精子。本研究通过受控水族箱实验结合遗传父权分析（genetic paternity analysis），探究了偷配行为的时机对偷配雄性父权占比的影响。研究结果显示，在产卵启动后约1小时内提前侵入巢穴，可显著提升偷配雄性的父权占比。这一现象的部分原因可能是，提前释放的精子可保持活性数小时，并能对后续产出的卵子完成受精。另一潜在机制为：雌性在产卵的首个小时内即可产出约70%的总产卵量。上述研究结果表明，提前偷配可最大化偷配雄性的受精机会，这大概率是对长时间产卵过程以及精子长存活时长的适应性演化策略。本研究提出，在解析体外受精物种的精子竞争后果时，需考虑精子释放的时机与顺序——这类物种的精子释放与受精之间存在时间差，与体内受精（internal fertilisation）物种的情形相似。