每日英語跟讀 Ep.K622: Scientists Discover Unprecedented "Virgin Birth" of Crocodile at Costa Rica Zoo
Researchers have made an extraordinary finding at a zoo in Costa Rica, as they document the first-known case of a "virgin birth" by a crocodile that had been isolated for 16 years. The female American crocodile laid 14 eggs in 2018 within her enclosure, a relatively common occurrence among captive reptiles. However, the true surprise came when one of the eggs was discovered to contain a fully formed stillborn baby crocodile after three months of incubation.
研究人員在哥斯大黎加的一個動物園達成了一項非凡的調查，他們記錄了鱷魚「孤雌生殖」的首例，而這隻鱷魚在動物園獨居了16年。這隻美洲鱷於2018年在圈養環境下產下了14個蛋，這對圈養爬行動物來說是相對常見的現象。然而，真正的驚喜出現在經過三個月孵化後，其中一個蛋被發現含有一隻完整的鱷魚寶寶死胎。
In a study published in the journal Biology Letters, scientists examined the genetic composition of the crocodile fetus. They identified DNA sequences indicating that the fetus resulted from facultative parthenogenesis (FP), a form of reproduction that does not involve the genetic contribution of males. Although this phenomenon, also known as a "virgin birth," has been observed in other species such as fish, birds, lizards, and snakes, this marks the first recorded instance in a crocodile.
在發表於《生物學報》期刊的研究中，科學家們檢驗了這隻鱷魚胎兒的基因組成。他們發現DNA序列表明這個胎兒是由「真孤雌生殖」（FP）產生的，即無需雄性基因參與的一種繁殖形式。雖然這種現象，也被稱為「處女生殖」，在其他物種如魚類、鳥類、蜥蜴和蛇類中已被觀察到，但這是首次在鱷魚中出現的記錄。
FP occurs when a female's egg cell develops into a viable offspring without being fertilized by a male's sperm cell. During the process of egg cell formation, a precursor cell divides into four cells. While one of these cells becomes the egg cell itself, retaining essential cellular structures and cytoplasm, the remaining cells contain extra genetic material. One of these additional cells functions similarly to a sperm cell, fusing with the egg and initiating the process of fertilization.
「真孤雌生殖」是指雌性的卵細胞在沒有雄性精子受精的情況下發育成一個能夠存活的後代。在卵細胞形成過程中，一個前體細胞分裂成四個細胞。其中一個細胞成為卵細胞本身，保留著關鍵的細胞結構和細胞質，而其他細胞則含有額外的遺傳物質。其中一個額外的細胞類似於精子細胞，與卵細胞融合，啟動了受精的過程。
The American crocodile is currently classified as vulnerable and faces the risk of extinction in the wild. The study suggests that FP may be more prevalent among species nearing extinction. The scientists believe that the Costa Rica "virgin birth" could provide valuable insights into the reproductive capabilities of ancient crocodile ancestors that existed during the Triassic Period, approximately 250 million years ago. The findings could offer new knowledge about the reproductive mechanisms of archosaurian relatives, including members of Pterosauria and Dinosauria.
美洲鱷目前被列為易危物種，面臨野外滅絕的風險。研究表明，「真孤雌生殖」在接近滅絕的物種中可能更為普遍。科學家們認為哥斯大黎加的「處女生殖」發現可能為早在約2.5億年前三疊紀時期存在的古代鱷魚祖先的繁殖能力提供寶貴的洞察資料。這些發現可為翼龍目和恐龍亞目等主龍類近親相關的繁殖機制提供新的知識。
Reference article: https://www.reuters.com/world/americas/scientists-find-crocodile-virgin-birth-costa-rica-zoo-2023-06-07/