CAN'T find a mate? Try parthenogenesis. The type of asexual reproduction may be part of an extreme survival strategy for sharks.
找不到配偶？那就試試單性生殖！無性生殖也許將成為鯊魚的最終生存方式。
In parthenogenesis, females' eggs start dividing without being fertilised. This produces daughters that are genetically similar to themother. It was first oberved in a captive hammerhead shark in 2001,?but this was an isolated incident, and the shark pup died after three days,making it difficult to say much about its evolutionary significance.
在單性生殖中，雌性動物的卵無需受精即開始分裂。這會產(chǎn)下基因與母親相同的女兒。單性生殖最初是在2001年捕獲的一頭錘頭鯊身上發(fā)現(xiàn)的，不過，這只是一個孤立的事件，而且，鯊魚幼崽3天后就死了，因此，要對單性生殖的進化意義作比較多的闡述有點勉為其難。
Kevin Feldheim?at the Field Museum in Chicago, and an international team of colleagues, has now shown that the inc ident was not exceptional and sharks born from a virgin mother can survive for many years (Journal of Heredity, vol 101, p 374).
供職于芝加哥菲爾德博物館和遺傳研究國際組織的Kevin Feldheim表示，此次事例并非異常，由單性生殖母鯊產(chǎn)下的幼鯊可存活多年（見《遺傳雜志》第101期，374頁）。
The team was inspired by the 2001 birth to keep eggs produced by a captive white-spotted bamboo shark at the Belle Isle Aquarium of the Detroit Zoological Institute. The female had never encountered a male during her adult life and biologists had assumed the eggs were infertile. To their surprise seven incubated eggs produced two pups that survived five years before they were transferred to another facility. Genetic analysis confirmed that they were parthenogenesis.
受2001年錘頭鯊幼崽的啟發(fā)，該組織將一頭在底特律動物學研究所貝爾島水族館捕獲的白斑竹子鯊所產(chǎn)的卵作了保留處理。這頭母鯊在其成年期中未曾遇到過一頭雄鯊，生物學家們曾想當然地認為這些卵沒有生育力。但令他們驚奇的是，7只孵化的卵中竟孵化出了兩頭幼鯊，而這兩頭幼鯊在被轉移到另一個水族箱之前存活了5年。遺傳分析確認，它們系單性生殖。
"This suggests that parthenogenesis is a viableshark survival strategy," says Paulo Prod?hl?of Queen'sUniversity Belfast, UK, who is investigating a possible case of virgin birth in the whitetip reef shark.
“這暗示著單性生殖將成為行之有效的鯊魚繁殖法，”英國貝爾法斯特女王大學正研究白頂礁鯊單性生殖可能性的Paulo Prod?hl說。
Modern sharks have been on Earth for several hundred million years. One theory is that switching from sexual reproduction to virgin birth might have helped these ancient creatures survive so long. Prod?hl suggests virgin birth could have been a safeguard mechanism. Several shark species live in single-sex groups and he says parthenogenesis may have ensured that isolated populations of females could survive without males.
現(xiàn)代的鯊魚在地球上已存活了幾億年。一種理論言稱，或許是有性生殖到單性生殖的轉變才幫助了這些遠古的生物存活了這么長的時間。Prod?hl認為，單性生殖可能已成為一種保障機制。有幾個鯊魚物種以單性群的方式生存，他還說，單性生殖或許可保證隔離的雌鯊種群不靠雄鯊也能繁殖。
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