Why do cicadas come out every 17 years?
2024/5/31
But Why: A Podcast for Curious Kids
A
Andrew
专注于解决高质量训练数据和模型开发成本问题的 AI 研究员。
A
Anna
D
Dan Gruner
J
Jane Lindholm
K
Kieran
T
Tilda
Dan Gruner: 十七年蝉的周期性出现是一种进化适应，是为了躲避捕食者。通过以巨大的数量同时出现，它们可以压倒捕食者的捕食能力，确保种群的延续。这种策略的成功之处在于，捕食者无法在漫长的周期内记住蝉的出现时间，并且即使捕食者数量增加，也无法消灭所有蝉。此外，蝉的幼虫期在地下以植物的木质部汁液为食，这种汁液营养成分低，导致它们的发育周期很长。蝉的幼虫期经历多次蜕皮，每次蜕皮后体型都会增大，直到最后一次蜕皮长出翅膀，飞出地面。雄性蝉通过腹部内特殊的器官——鼓膜振动发出响亮的鸣叫声来吸引雌性交配，雌性蝉则将卵产在树枝上。
Jane Lindholm: 今年的蝉群出现格外引人注目，是因为两个不同周期的蝉群同时出现，这种现象非常罕见，上一次出现是在221年前。蝉的出现是一种令人兴奋的自然现象，因为它们数量巨大，行动缓慢，且不咬人，易于观察和互动。但大量蝉的出现也可能造成一些困扰，例如噪音和遍地的蝉蜕。
Anna: 蝉以植物的木质部汁液为食。
Kieran: 蝉蜕皮是为了长大，因为它们的表皮（外骨骼）不能随着身体长大而扩张。
Tilda: 蝉的繁殖方式是雌蝉将卵产在树枝上。
Andrew: 蝉在夜间出现的数量多于白天，可能是为了躲避捕食者。
Dan Gruner: The periodical cicadas' 17-year cycle is an evolutionary adaptation to avoid predators. By emerging in massive numbers simultaneously, they overwhelm the predatory capacity of their predators, ensuring the survival of the species. The success of this strategy lies in the fact that predators cannot remember the cicadas' emergence time over such a long cycle, and even if the number of predators increases, they cannot eliminate all the cicadas. In addition, the cicadas' larval stage feeds on the xylem sap of plants underground, which is low in nutrients, resulting in a long developmental cycle. The cicadas' larvae undergo multiple molts, and each molt increases in size until the final molt, when they grow wings and fly out of the ground. Male cicadas emit loud calls to attract females for mating by vibrating special organs—tymbals—in their abdomens, while female cicadas lay their eggs on tree branches.
Jane Lindholm: This year's cicada emergence is particularly striking because two different cyclical groups of cicadas have emerged simultaneously, a very rare phenomenon, the last time occurring 221 years ago. The emergence of cicadas is an exciting natural phenomenon because they are numerous, slow-moving, and do not bite, making them easy to observe and interact with. However, the emergence of large numbers of cicadas can also cause some inconvenience, such as noise and the shedding of cicada skins all over the place.
Anna: Cicadas feed on the xylem sap of plants.
Kieran: Cicadas molt to grow larger because their exoskeleton cannot expand as their bodies grow.
Tilda: Cicadas reproduce by the female cicada laying eggs on tree branches.
Andrew: More cicadas emerge at night than during the day, possibly to avoid predators.
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