The Jellies That Evolved a Different Way To Keep Time
A new species of hydrozoan jellyfish keeps time in its own way.
一种新的水螅水母物种以自己的方式计时。
Kristina Armitage/ Quanta Magazine
克里斯蒂娜·阿米蒂奇/广达杂志
The passage of the sun across the sky — dawn, day, dusk, night — drives the clock of life.
太阳穿过天空的过程——黎明、白天、黄昏、夜晚——驱动着生命的时钟。
Some species wake with the sun and sleep with the moon.
有些物种随太阳醒来，随月亮入眠。
Others do the opposite, and a few keep odd hours.
其他人则相反，还有一些人的工作时间很奇怪。
These naturally driven, 24-hour biological cycles are known as circadian rhythms, and they do more than cue bedtime: They regulate hormones, metabolism, DNA repair, and more.
这些自然驱动的 24 小时生物周期被称为昼夜节律，它们的作用不仅仅是提示就寝时间：它们还调节激素、新陈代谢、DNA 修复等。
When life falls out of sync, there can be dire consequences for health, reproduction, and survival.
当生命不同步时，可能会对健康、繁殖和生存造成可怕的后果。
Lacking watches, many species keep time using an internal system — a set of interacting genes and their protein products that effectively keeps track of a 24-hour period — that is calibrated by sunlight.
许多物种没有手表，而是使用内部系统来计时，该系统是一组相互作用的基因及其蛋白质产物，可以有效地记录 24 小时周期，并通过阳光进行校准。
This kind of circadian clock is widespread, found even in single-celled algae , which suggests that biological timekeeping evolved billions of years ago.
这种生物钟很普遍，甚至在单细胞藻类中也有发现，这表明生物计时在数十亿年前就已经进化了。
Across animals, most species have the same genetic system, using genes known as CLOCK , BMAL1 , and CRY , or recognizable homologues.
在动物中，大多数物种都具有相同的遗传系统，使用称为 CLOCK 、 BMAL1 和 CRY 的基因或可识别的同源物。
This form of biological clock mechanism appears even in ancient lineages, including sponges and some jellyfish.
这种形式的生物钟机制甚至出现在古老的谱系中，包括海绵和一些水母。
But is this the only way to do it?
但这是唯一的方法吗？
In a pea-size jelly off the coast of Japan, biologists are examining a different kind of timekeeping.
在日本海岸附近的豌豆大小的水母中，生物学家正在研究一种不同的计时方式。
Somewhere over the course of their evolution, the class of hydrozoans — which includes certain kinds of jellyfish, hydras, and colonial siphonophores such as the Portuguese man-of-war — lost the genes that operate circadian clocks in the rest of the animal kingdom.
在进化过程中的某个时刻，水螅类动物——包括某些种类的水母、水螅和殖民管水母动物，如葡萄牙战舰——失去了动物界其他动物控制生物钟的基因。
Yet a newly discovered hydrozoan jellyfish species has a mysterious circadian clock that regularly tracks 20-hour periods, suggesting that its mechanism evolved independently.
然而，一种新发现的水螅水母物种拥有神秘的生物钟，有规律地追踪 20 小时的周期，这表明其机制是独立进化的。
The findings, published in PLOS Biology in January 2026, push the limits of what chronobiologists consider “circadian.”
该研究结果于 2026 年 1 月发表在 PLOS Biology 上，突破了时间生物学家认为的“昼夜节律”的极限。
“We’ve wondered, do jellyfish have real clocks?” said Ann Tarrant , who studies circadian rhythms in sea anemones at the Woods Hole Oceanographic Institution and was not involved in the research.
“我们想知道，水母有真正的时钟吗？”安·塔兰特（Ann Tarrant）说道，她在伍兹霍尔海洋研究所研究海葵的昼夜节律，但并未参与这项研究。
“This study is really exciting because it shows a clock in this animal that’s lost some of these genes that we think are essential for circadian regulation in most other animals.”
“这项研究确实令人兴奋，因为它表明这种动物的生物钟丢失了一些基因，我们认为这些基因对于大多数其他动物的昼夜节律调节至关重要。”
The clock found in this jellyfish, a new species to science, is unusual not only because it tracks 20 hours, instead of Earth’s 24-hour day length, but also because it seems to be paired with a molecular timer that counts down from sunrise until it’s time for the jellyfish to spawn.
这种水母是科学上的一个新物种，它的时钟很不寻常，不仅因为它记录的是 20 小时，而不是地球的 24 小时白天长度，而且还因为它似乎与一个分子计时器配对，从日出开始倒计时，直到水母产卵的时间。
This surprising mechanism suggests that scientists may be overlooking unconventional clocks across the tree of life.
这种令人惊讶的机制表明，科学家可能忽视了生命树上的非常规时钟。
“Systems like this might be much more widespread, and we are not looking, because we only look at these genetic components, [the animal CLOCK genes],” said Ezio Rosato , a chronobiologist at the University of Leicester who penned a scientific commentary about the work.
莱斯特大学的时间生物学家埃齐奥·罗萨托 (Ezio Rosato) 写了一篇关于这项工作的科学评论，他说：“这样的系统可能更为普遍，但我们没有关注，因为我们只关注这些遗传成分，[动物时钟基因]。”
“You could make a clock with any molecular mechanism.
“你可以用任何分子机制制造一个时钟。
All you need is a series of reactions which are organized in a certain way.”
你所需要的只是一系列以某种方式组织起来的反应。”
Once a quarter, Ryusaku Deguchi brings his students at Miyagi University of Education to Izushima, a 1-square-mile island in Sendai Bay along Japan’s northeastern coast.
每个季度，出口龙作都会带着宫城教育大学的学生来到日本东北海岸仙台湾的一座面积为 1 平方英里的岛屿——伊豆岛。
There, thousands of translucent orbs smaller than peas bob in the water column below the fishing dock.
在那里，钓鱼码头下方的水柱中漂浮着数千个比豌豆还小的半透明球体。
He and his students collect these jellyfish specimens, representing more than a dozen species, and rear them in the lab to study their reproductive cycles.
他和他的学生收集了这些代表十多个物种的水母标本，并将它们放在实验室中饲养以研究它们的生殖周期。
Sendai Bay, off the northeastern coast of Japan, as seen from Izushima, a small offshore island inhabited by only a few dozen fishers and shellfish farmers.
仙台湾位于日本东北海岸，从伊豆岛看到，这是一个只有几十名渔民和贝类养殖者居住的近海小岛。
When Ruka Kitsui was a freshman in college, he was one of those students.
当Ruka Kitsui还是大学一年级学生时，他就是其中之一。
Observing jellyfish gametes develop under a microscope lured him away from the neat logic of physics and chemistry and into the dynamic processes of biology.
在显微镜下观察水母配子的发育，使他远离了物理和化学的简洁逻辑，进入了生物学的动态过程。
Later, he joined Deguchi’s lab to study invertebrate development and dedicated his master’s thesis to jellyfish reproduction, homing in on an unusual population among the specimens.
后来，他加入了口口的实验室，研究无脊椎动物的发育，并将他的硕士论文奉献给了水母繁殖，重点关注样本中不寻常的种群。
Many of Deguchi’s jellyfish spawned daily, releasing their eggs and sperm into the water, usually shortly after sunrise.
许多出口水母每天都会产卵，通常在日出后不久将卵子和精子释放到水中。
But these jellyfish were odd: They spawned at night.
但这些水母很奇怪：它们在晚上产卵。
For species that reproduce through mass spawning, including some corals and jellyfish, accurate timekeeping is crucial.
对于通过大量产卵繁殖的物种（包括一些珊瑚和水母）来说，准确的计时至关重要。
They release gametes directly into the water, leaving fertilization to chance: If there aren’t sperm in the water when eggs arrive, there will be no next generation.
它们将配子直接释放到水中，使受精成为可能：如果卵子到达时水中没有精子，就不会产生下一代。
So these species have evolved various molecular mechanisms to sync up their spawning, often using proteins that sense and respond to light signals.
因此，这些物种进化出了各种分子机制来同步产卵，通常使用感知光信号并做出反应的蛋白质。
Kitsui knew there had to be some molecular mechanism behind his jellies’ sundown clock.
Kitsui 知道他的水母的日落时钟背后一定存在某种分子机制。
But the absence of an obvious light trigger made the night-spawning behavior a puzzle.
但由于缺乏明显的光触发因素，夜间产卵行为成为一个谜。
After taking a class with Ryusaku Deguchi (left) at Miyagi University of Education in Japan, Ruka Kitsui (right) became captivated by the mechanisms of jellyfish development.
在日本宫城教育大学与 Ryusaku Deguchi（左）一起上课后，Ruka Kitsui（右）对水母的发育机制着迷。
He began with a series of light experiments.
他从一系列光实验开始。
First he kept female jellyfish in a cycle of 12 hours of artificial light and 12 hours of darkness — roughly reflecting the natural day-night cycle at Izushima.
首先，他让雌性水母处于 12 小时人造光和 12 小时黑暗的周期中——大致反映了伊豆岛的自然昼夜周期。
Each time, precisely two hours after “dusk,” female jellies released their eggs into the water.
每次，在“黄昏”后两小时，雌性水母都会将卵释放到水中。
At first, Kitsui and Deguchi assumed that the transition from light to dark was the spawning signal.
起初，Kitsui 和 Deguchi 认为从亮到暗的转变是产卵信号。
But when they turned the lights on two hours earlier, making “dawn” happen sooner but leaving “dusk” at the same time, the jellyfish spawned two hours earlier as well.
但当他们提前两个小时开灯，让“黎明”提前到来，但同时也离开“黄昏”时，水母也提前了两个小时产卵。
What would the jellies do under continuous sunlight?
在持续的阳光照射下，水母会做什么？
To Kitsui’s surprise, the jellyfish spawned every 20 hours on their own, without a specific cue.
令 Kitsui 惊讶的是，水母每 20 小时就会自行产卵一次，没有任何特定提示。
This suggested that the previously unknown jellyfish species — dubbed Clytia sp.
这表明以前未知的水母物种——被称为 Clytia sp。
IZ-D until it receives a formal name — had some kind of internally driven circadian rhythm.
IZ-D 在获得正式名称之前——具有某种内部驱动的昼夜节律。
“In that instant, I felt the true joy at the core of research: uncovering something that no one in the world had known before,” he said.
“在那一刻，我感受到了研究核心的真正快乐：发现了世界上以前没有人知道的东西，”他说。
Kitsui knew that C.
Kitsui知道C.
sp.
sp。
IZ-D’s clock wasn’t made of the clock genes widespread in animals; this hydrozoan lineage had lost those over evolutionary time.
IZ-D 的生物钟并非由动物体内普遍存在的生物钟基因构成；而是由生物钟基因组成。随着进化时间的推移，这种水螅动物谱系已经失去了这些特征。
Yet it fit nearly all the requirements that chronobiologists have described for circadian clocks.
然而它几乎符合时间生物学家描述的生物钟的所有要求。
A circadian clock must be self-sustained and internally driven, as the 20-hour cycle of the jellies’ spawning is.
生物钟必须是自我维持和内部驱动的，就像水母产卵的 20 小时周期一样。
It must also be regulated by an environmental stimulus such as light; while the jellies’ spawning clock can run on a 20-hour cycle under persistent light in the lab, in nature it resets every day.
它还必须受到环境刺激（例如光）的调节；虽然水母的产卵时钟在实验室的持续光照下可以以 20 小时为一个周期运行，但在自然界中它每天都会重置。
And a true circadian rhythm, like ours, should also be unaffected by temperature.
真正的昼夜节律，就像我们一样，也应该不受温度的影响。
In Kitsui’s experiments, however, warmer water made the 20-hour clock faster and cooler water made it slower.
然而，在 Kitsui 的实验中，温暖的水使 20 小时时钟走得更快，而冷水则让它走得更慢。
It is a molecular biological clock, but not in the way scientists typically define them.
它是一个分子生物钟，但与科学家通常定义的方式不同。
“I wonder how [this] will be perceived in the chronobiology field,” said Kristin Tessmar-Raible , a chronobiologist at the Alfred Wegener Institute and the University of Vienna who was not involved in the research.
“我想知道时间生物学领域会如何看待这一点，”阿尔弗雷德韦格纳研究所和维也纳大学的时间生物学家克里斯汀·泰斯马尔-拉布尔（Kristin Tessmar-Raible）说，她没有参与这项研究。
Is it a true circadian rhythm if it breaks any of the three rules?
如果违反这三个规则中的任何一个，这就是真正的昼夜节律吗？
“Or will we, as a community, take it as something [else]?”
“或者，作为一个社区，我们会将其视为[其他]吗？”
But the 20-hour circadian clock couldn’t fully explain the jellies’ sunset spawning behavior.
但 20 小时生物钟无法完全解释水母日落产卵的行为。
There had to be another piece to this clockwork mechanism.
这个发条装置必须有另一个部件。
To understand more about what was going on in their new species, Deguchi and Kitsui turned to Clytia hemisphaerica , a close relative.
为了更多地了解他们的新物种的情况，出口和Kitsui转向了Clytia hemisphaerica，它的近亲。
C.
C.
hemisphaerica is visually identical to C.
hemisphaerica 在视觉上与 C.
sp.
sp。
IZ-D, with a transparent bell and long, trailing tentacles.
IZ-D，有透明的铃铛和长长的拖尾触手。
Crucially, it is a well-studied animal model , and the details of its spawning and reproduction are well known.
至关重要的是，它是一种经过充分研究的动物模型，其产卵和繁殖的细节众所周知。
Eager for answers, they pulled in their friend Tsuyoshi Momose, a developmental biologist at the French National Center for Scientific Research and an expert on the species.
为了寻求答案，他们请来了朋友 Tsuyoshi Momose，他是法国国家科学研究中心的发育生物学家，也是该物种的专家。
Clytia hemisphaerica , a model species for invertebrate reproduction, has two phases: sessile polyp (left) and free-floating medusa (right).
Clytia hemisphaerica 是无脊椎动物繁殖的模式物种，有两个阶段：无蒂息肉（左）和自由漂浮的水母（右）。
Plankton Chronicals (left); Marion Lechable and Alexandre Jan
浮游生物编年史（左）；马里昂·勒查布尔和亚历山大·扬
Every day, two hours after sunrise, C.
每天，日出后两小时，C.
hemisphaerica spawns.
半球菌产卵。
This process begins with the day’s first light, when photoreceptive proteins called opsins in the gonads detect sunlight, triggering production of a hormone that matures developing gametes.
这个过程从一天的第一缕阳光开始，此时性腺中称为视蛋白的感光蛋白检测到阳光，触发一种激素的产生，使正在发育的配子成熟。
The team suspects that the new species C.
研究小组怀疑新物种C.
sp.
sp。
IZ-D has a slightly tweaked version of this mechanism in which the hormone is released slowly over time, dragging out the gamete maturation process to around 14 hours.
IZ-D 对该机制进行了稍微调整，其中激素随着时间的推移缓慢释放，将配子成熟过程拖到大约 14 小时。
Once enough of the hormone has accumulated and the gametes have fully developed, the jellies spawn simultaneously — roughly two hours after sunset, like clockwork.
一旦积累了足够的激素并且配子完全发育，水母就会同时产卵——大约在日落后两小时，就像发条一样。
“For me, as a chronobiologist, it is very interesting to see a system getting a different level of organization using almost the same tools that you had before,” Rosato said.
“对我来说，作为一名时间生物学家，看到一个系统使用与以前几乎相同的工具获得不同级别的组织是非常有趣的，”罗萨托说。
“Just a little change” — slower hormone accumulation and therefore a slower gamete maturation process — “creates a much more complex level of organization.”
“只要一点点改变”——激素积累速度减慢，配子成熟过程减慢——“就会产生更加复杂的组织水平。”
Next, Momose, Deguchi, and Kitsui plan to compare the genomes of C.
接下来，Momose、Deguchi 和 Kitsui 计划比较 C.
hemisphaerica and C.
半球形和C.
sp.
sp。
IZ-D to explore the molecular mechanisms at play in the 20-hour quasi-circadian clock and the 14-hour sunrise countdown timer.
IZ-D 旨在探索 20 小时准生物钟和 14 小时日出倒计时器中发挥作用的分子机制。
And in April 2026, Kitsui will start a doctorate program focused on clam reproduction at Tohoku University, where he can continue describing the quirks of invertebrate development.
2026 年 4 月，Kitsui 将在东北大学启动一个专注于蛤类繁殖的博士学位课程，在那里他可以继续描述无脊椎动物发育的怪异现象。
Already, the unusual clock he stumbled upon has made an impact on the field.
他偶然发现的这款不寻常的时钟已经在这个领域产生了影响。
“It’s just a beautiful study that’ll inspire a lot more work,” Tarrant said.
“这是一项美妙的研究，将激发更多的工作，”塔兰特说。
“It highlights that there’s novelty and diversity and perhaps completely different pathways, and it gives us some examples of how you can be really creative in studying those mechanisms.”
“它强调了新颖性和多样性，也许还有完全不同的途径，它给我们提供了一些例子，说明如何在研究这些机制时真正发挥创造力。”
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