VOA科学技术2024--Pregnant Stingray Offers Rare Lesson of Biology

Pregnant Stingray Offers Rare Lesson of Biology

　　Charlotte has spent much of her life in captivity¹ at a non-profit aquarium² in North Carolina's Appalachian Mountains. She is an ocean animal called a round stingray.

　　She is about 3,700 kilometers from her natural habitat in the Pacific Ocean off southern California. And she has not shared space with a male of her species in at least eight years.

　　But Charlotte is about to give birth. The reddish-brown stingray is pregnant with as many as four young, called pups. They were created by a rare process of natural reproduction called parthenogenesis. A female animal develops an egg into an embryo³ without fertilization material from a male.

　　Charlotte will give birth to her young at home: Team ECCO Aquarium and Shark Lab on Main Street in Hendersonville. Brenda Ramer formed the organization and serves as its chief.

　　She said, when caretakers first noticed a lump on Charlotte's back, they thought it might be a cancerous growth. So, they examined the animal with an ultrasound machine, which makes images using sound. The images showed that Charlotte was pregnant.

　　The aquarium team was shocked.

　　"We were all like, ‘Shut the back door. There's no way,'" Ramer said. "We thought we were overfeeding her. But we were overfeeding her because she has more mouths to feed."

　　The small aquarium encourages local schoolchildren and others to take an interest in science. Now, they are getting a real-life lesson few witness. Parthenogenesis can happen in some insects, fish, amphibians⁴, birds and reptiles⁵, but it is extremely unusual. Documented examples have included California condors⁶, Komodo dragons and yellow-bellied water snakes.

　　Kady Lyons is a research scientist at the Georgia Aquarium in Atlanta. She is not connected to the North Carolina aquarium. She said Charlotte's pregnancy⁷ is the only documented example of parthenogenesis in the round stingray that she knows of.

　　But Lyons is not shocked. Other kinds of rays, and related fish such as sharks, have had these kinds of pregnancies⁸ under human care.

　　"I'm not surprised, because nature finds a way of having this happen," she said.

　　To be clear, Lyons said, these animals are not cloning themselves. Instead, a female's egg joins with another cell in the female. This leads to cell division and creation of an embryo.

　　"We don't know why it happens," Lyons said. "Just that it's kind of this really neat phenomenon that they seem to be able to do."

　　Charlotte lives in a tank of about 8,300 liters of water. Ramer said the aquarium is hoping to get a tank nearly twice that size for Charlotte's young. They also want to put live cameras up for people to see them.

　　"It is very rare to happen," Ramer said. "But it's happening in the middle of the Blue Ridge⁹ Mountains in rural North Carolina, hundreds of miles from the ocean."

　　Round stingrays like Charlotte are common along the Pacific Ocean coasts of southern California and Mexico. They often rest on the ocean's sandy bottom near land.

　　In the wild, they are about the size of a food plate. They come in all shades of brown. They eat small animals like worms, crabs¹⁰ and mollusks. And round stingrays are sometimes eaten by sharks, seals and giant sea bass¹¹.

　　The round ray is well known to humans who like to go in the ocean. The ray can sting when stepped on.

　　Lyons finds the species fascinating.

　　"I'm glad the round stingray is getting the media attention that it deserves," Lyons said. "It's not necessarily as sexy as a white shark, but they do a lot of really neat stuff."

　　Words in This Story

　　aquarium –n. a tank that holds fish or a building that keeps fish for the public to see and enjoy

　　habitat –n. the environment in which a plant or animal lives

　　encourage –v. to cause someone to do something

　　cloning –n. the process of making an exact genetic¹² copy of a living thing

　　phenomenon –n. an event that happens for a reason which can be described and studied

　　shade –n. the level of brightness or darkness that a color has

　　fascinating –adj. very interesting and worth attention

　　neat –adj. (informal) interesting or fun

1 captivity   

n.囚禁；被俘；束缚

参考例句：

• A zoo is a place where live animals are kept in captivity for the public to see.动物园是圈养动物以供公众观看的场所。
• He was held in captivity for three years.他被囚禁叁年。

2 aquarium   

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。

3 embryo   

n.胚胎，萌芽的事物

参考例句：

• They are engaging in an embryo research.他们正在进行一项胚胎研究。
• The project was barely in embryo.该计划只是个雏形。

4 amphibians   

两栖动物( amphibian的名词复数 )； 水陆两用车； 水旱两生植物； 水陆两用飞行器

参考例句：

• The skin of amphibians is permeable to water. 两栖动物的皮肤是透水的。
• Two amphibians ferry them out over the sands. 两辆水陆两用车把他们渡过沙滩。

5 reptiles   

n.爬行动物，爬虫( reptile的名词复数 )

参考例句：

• Snakes and crocodiles are both reptiles. 蛇和鳄鱼都是爬行动物。 来自《简明英汉词典》
• Birds, reptiles and insects come from eggs. 鸟类、爬虫及昆虫是卵生的。 来自《现代汉英综合大词典》

6 condors   

n.神鹰( condor的名词复数 )

参考例句：

• What would our condors feed on if no one was in danger? 你不发生危险，那我们秃鹰吃啥呢？ 来自互联网
• Yo mama so fat she has been declared a natural habitat for Condors. Yomama是如此之肥，她被定为秃鹰的自然栖息地。 来自互联网

7 pregnancy   

n.怀孕，怀孕期

参考例句：

• Early pregnancy is often accompanied by nausea.怀孕早期常有恶心的现象。
• Smoking during pregnancy increases the risk of miscarriage.怀孕期吸烟会增加流产的危险。

8 pregnancies   

怀孕，妊娠( pregnancy的名词复数 )

参考例句：

• Since the wartime population needed replenishment, pregnancies were a good sign. 最后一桩倒不失为好现象，战时人口正该补充。
• She's had three pregnancies in four years. 她在四年中怀孕叁次。

9 ridge   

n.山脊；鼻梁；分水岭

参考例句：

• We clambered up the hillside to the ridge above.我们沿着山坡费力地爬上了山脊。
• The infantry were advancing to attack the ridge.步兵部队正在向前挺进攻打山脊。

10 crabs   

n.蟹( crab的名词复数 )；阴虱寄生病；蟹肉v.捕蟹( crab的第三人称单数 )

参考例句：

• As we walked along the seashore we saw lots of tiny crabs. 我们在海岸上散步时看到很多小蟹。 来自《简明英汉词典》
• The fish and crabs scavenge for decaying tissue. 鱼和蟹搜寻腐烂的组织为食。 来自《简明英汉词典》

11 bass   

n.男低音(歌手)；低音乐器；低音大提琴

参考例句：

• He answered my question in a surprisingly deep bass.他用一种低得出奇的声音回答我的问题。
• The bass was to give a concert in the park.那位男低音歌唱家将在公园中举行音乐会。

12 genetic   

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。