澳大利亚研究团队发现，看似最简单的动物——海绵——能够通过日落这一环境线索触发复杂的生理变化。1研究表明，日落会触发海绵幼虫DNA中与定居和变态相关的基因区域的表观修饰，使其被激活为"可及"状态。1这一机制使幼虫能够在约30分钟内快速完成附着并开始分解其幼虫体。1
此前2020年的研究曾发现，若阻止海绵幼虫体经历日落，即使在优质海藻附近也不会定居。1新研究进一步揭示了这一现象的分子基础：日落充当了一种生物信号，提前调整幼虫DNA的可及性，为即将发生的变态做好准备。1值得注意的是，海绵体内控制这一过程的CLOCK基因也调控人类的昼夜节律。1作为现存最古老的动物类群之一，距今约7亿年历史的海绵，其这一适应机制展现了无神经系统动物如何通过环境信号进行精密的生理过程协调。1
Australian researchers have discovered that brainless sea sponges rely on sunset as an environmental cue to trigger genetic changes that prepare them for metamorphosis.1 The study reveals that when sponge larvae experience the dimming light at sunset, they activate DNA modifications that open up genetic regions associated with settlement and metamorphosis, positioning them to undergo rapid transformation.1 This process occurs approximately 30 minutes after the larvae detect the sunset signal and begin attaching to a surface.1
The findings demonstrate a sophisticated biological coordination mechanism in organisms that lack a nervous system.1 Earlier research from 2020 showed that sponge larvae would not settle even near high-quality algae if prevented from experiencing sunset, underscoring the critical importance of this environmental signal.1 The new research uses chromatin accessibility analysis to reveal the molecular mechanism behind this behavior, showing how the organisms pre-activate genes necessary for settling and metamorphosis in response to light cues.1
Notably, the genetic CLOCK gene found in sponges, which regulates this response to sunset, also controls circadian rhythms in humans.1 Sea sponges represent one of the oldest existing animal groups, with an evolutionary history spanning approximately 700 million years.1
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