鲨鱼单性繁殖后代的存活时间更长-凯发k8官网

鲨鱼单性繁殖后代的存活时间更长
文章来源:未知 文章作者:meng 发布时间:2010-01-26 03:16 字体: [ ] 
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shark pups幼兽,小狗 born to 1 mothers can survive over the long-term, according to new research published jan. 25, 2010 in the journal of heredity. the study shows for the first time that some virgin births can result in viable能养活的,能生育的 offspring后代,子孙. 3 analysis led by a field museum scientist working with numerous colleagues has confirmed the first known case of a virgin female shark producing multiple offspring that survived. two daughters of the white-spotted bamboo shark竹子鲨 are now more than five years old. earlier research proved that reproduction occurred in two other shark species without aid of male 4, a phenomenon called parthenogenesis单性生殖, but the offspring did not survive in those cases.

dr. kevin feldheim, manager of the pritzker laboratory for 5 systematics and evolution at the field museum, 6 the sharks' genetic material to rule out排除 any 7父亲的 reproduction assistance.

"examination of highly variable易变的,多变的 sections of the genome prove that these young sharks had no father," feldheim said. "these findings are 8 because they tell us that some female sharks can produce litters一窝 of offspring without ever having mated with a male.

"we compared several sections of the genome between two of the young sharks and their mother. it turned out that all the genetic material in each of the young ones came from the mother, proving there was no father."

although the shark mother was kept in a tank at the 9 10 11 in detroit where only another female of a different but related species resided, genetic testing was required to rule out the possibility that the female shark could have encountered male sperm earlier in her life.

a second analysis using more general techniques to examine more than a hundred additional regions of the genome was performed by séan fitzpatrick, ph.d. student, and dr. paulo prodöhl, head of the fish genetics and molecular ecology laboratory, of queen's university in belfast, to confirm feldheim's finding.the analysis found that the young sharks didn't share all their mother's genetic material and aren't true clones of her, but more like "half-clones," said feldheim.

parthenogenesis occurs when an egg or ovum卵子 fuses with与……融合 a cell called a sister polar body极体, a byproduct副产品 of ova卵细胞 production, rather than with male sperm, to promote cell division. the sister polar body is nearly 12 identical to the ovum, said dr. demian chapman of the institute for ocean conservation science at 13 14 university, co-author of the current study and lead author in earlier studies of virgin shark births.

despite the lack of genetic diversity involved in omitting sperm from the process, "parthenogenesis may not be as much of a dead-end mode of reproduction as we thought for these sharks," chapman said.

douglas sweet, who 15 worked at the detroit aquarium水族馆, 16 to incubate孵化,培养 the bamboo shark eggs when he discovered an apparent virgin had produced them because of earlier experiences elsewhere that suggested virgin shark reproduction.

sweet, now 17负责人,主管 of the london state fish hatchery in london, ohio, said that studies have confirmed asexual reproduction无性繁殖 in sharks that bear offspring live and those that deposit eggs. this leads to interesting genetic and conservation implications.

it could mean that a bamboo shark finding herself 18 on a small reef with no male in the vicinity在附近 could produce offspring in hopes that male suitors求婚者,请愿者 may eventually find their way to her daughters. "sharks have been around for hundreds of millions of years," sweet said. "i suspect they have some pretty interesting survival strategies that we are only now becoming aware of."



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1 phpwj     
n.处女,未婚女子;adj.未经使用的;未经开发的
参考例句:
  • have you ever been to a virgin forest?你去过原始森林吗?
  • there are vast expanses of virgin land in the remote regions.在边远地区有大片大片未开垦的土地。
2 mi2wz     
adj.可行的,切实可行的,能活下去的
参考例句:
  • the scheme is economically viable.这个计划从经济效益来看是可行的。
  • the economy of the country is not viable.这个国家经济是难以维持的。
3 pgixp     
adj.遗传的,遗传学的
参考例句:
  • it's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
  • each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。
4 jfozo     
n.精子,精液
参考例句:
  • only one sperm fertilises an egg.只有一个精子使卵子受精。
  • in human reproduction,one female egg is usually fertilized by one sperm.在人体生殖过程中,一个精子使一个卵子受精。
5 me9xh     
adj.分子的;克分子的
参考例句:
  • the research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
  • for the pressure to become zero, molecular bombardment must cease.当压强趋近于零时,分子的碰撞就停止了。
6 483f1acae53789fbee273a644fdcda80     
v.分析( analyze的过去式和过去分词 );分解;解释;对…进行心理分析
参考例句:
  • the doctors analyzed the blood sample for anemia. 医生们分析了贫血的血样。 来自《简明英汉词典》
  • the young man did not analyze the process of his captivation and enrapturement, for love to him was a mystery and could not be analyzed. 这年轻人没有分析自己蛊惑著迷的过程,因为对他来说,爱是个不可分析的迷。 来自《简明英汉词典》
7 l33zv     
adj.父亲的,像父亲的,父系的,父方的
参考例句:
  • i was brought up by my paternal aunt.我是姑姑扶养大的。
  • my father wrote me a letter full of his paternal love for me.我父亲给我写了一封充满父爱的信。
8 8vbx6     
adj.显著的,异常的,非凡的,值得注意的
参考例句:
  • she has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
  • these cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。
9 mqly5     
n.靓女
参考例句:
  • she was the belle of her sunday school class.在主日学校她是她们班的班花。
  • she was the belle of the ball.她是那个舞会中的美女。
10 fatze     
n.小岛,岛
参考例句:
  • he is from the isle of man in the irish sea.他来自爱尔兰海的马恩岛。
  • the boat left for the paradise isle of bali.小船驶向天堂一般的巴厘岛。
11 gvszl     
n.水族馆,养鱼池,玻璃缸
参考例句:
  • the first time i saw seals was in an aquarium.我第一次看见海豹是在水族馆里。
  • i'm going to the aquarium with my parents this sunday.这个星期天,我要和父母一起到水族馆去。
12 lgixo     
adv.遗传上
参考例句:
  • all the bees in the colony are genetically related. 同一群体的蜜蜂都有亲缘关系。
  • genetically modified foods have already arrived on american dinner tables. 经基因改造加工过的食物已端上了美国人的餐桌。 来自英汉非文学 - 生命科学 - 基因与食物
13 qu1wx     
adj.石头的,多石头的,冷酷的,无情的
参考例句:
  • the ground is too dry and stony.这块地太干,而且布满了石头。
  • he listened to her story with a stony expression.他带着冷漠的表情听她讲经历。
14 psiyg     
n.小河,溪;v.忍受,容让
参考例句:
  • in our room we could hear the murmur of a distant brook.在我们房间能听到远处小溪汩汩的流水声。
  • the brook trickled through the valley.小溪涓涓流过峡谷。
15 ni3x9     
adv.从前,以前
参考例句:
  • we now enjoy these comforts of which formerly we had only heard.我们现在享受到了过去只是听说过的那些舒适条件。
  • this boat was formerly used on the rivers of china.这船从前航行在中国内河里。
16 lvqzzd     
adj.决定了的,坚决的;明显的,明确的
参考例句:
  • this gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
  • there is a decided difference between british and chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。
17 vstwv     
n.监督人,主管,总监;(英国)警务长
参考例句:
  • he was soon promoted to the post of superintendent of foreign trade.他很快就被擢升为对外贸易总监。
  • he decided to call the superintendent of the building.他决定给楼房管理员打电话。
18 bqmztd     
adj.与世隔绝的
参考例句:
  • his bad behaviour was just an isolated incident. 他的不良行为只是个别事件。
  • patients with the disease should be isolated. 这种病的患者应予以隔离。
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