Sharks are scary animals in the ocean， primarily for their big size and sharp teeth. Sharks have been around for hundreds of millions of years， and while they continue to evolve， they are also in grave danger. However， humans are a larger threat to sharks than sharks are to us. There are more than 500 species of shark. Given that there are a large number of unique species， some characteristics may be true for one species， but not another.

鯊魚是海洋中令人聞風喪膽的動物，主要是因為它們巨大的體型和鋒利的牙齒。鯊魚已經(jīng)存在了數(shù)億年，在不斷進化的同時，它們也處于極大的危險之中。但是，我們對鯊魚的威脅遠超過它們對我們的威脅?，F(xiàn)存有500多種鯊魚，但由于大量品種有其獨特性，某些特征可能在一個品種身上有，在另一個品種身上就沒有。

Sharks can live for hundreds of years.

鯊魚可以活數(shù)百年。

Sharks have one of the longest life spans compared with other animals.

The Greenland shark is the longest-living known vertebrate on Earth， according to a 2016 study published in the journal Science. Researchers using radiocarbon dating determined that the North Atlantic species likely lives an average of at least 272 years， and often doesn’t reach maturity until 150 years of age. Greenland sharks can live for at least 400 years， scientists have estimated.

與其他動物相比，鯊魚是壽命最長的動物之一。

《科學》雜志2016年發(fā)表的一項研究表明，格陵蘭鯊是地球上已知最長壽的脊椎動物。研究人員利用放射性碳測年法確定，北大西洋品種的平均壽命可能至少為272歲，它們通常要到150歲才成年?？茖W家估計，格陵蘭鯊的壽命至少可達400歲。

Sharks are older than trees and dinosaurs.

鯊魚比樹木和恐龍還要古老。

The earliest shark fossils date back as far as 450 million years， which means these creatures have been around at least 90 million years before trees and 190 million years before dinosaurs.

Sharks have been around since before Pangea broke apart， said Catherine Macdonald， lecturer at the University of Miami. Additionally， sharks have survived five mass extinctions， one of which wiped out around 96% of all marine life.

最早的鯊魚化石可以追溯到4.5億年前，這意味著這些生物的出現(xiàn)時間至少比樹木早9000萬年，比恐龍早1.9億年。

邁阿密大學的講師凱瑟琳·麥克唐納說，鯊魚在盤古大陸分裂之前就已經(jīng)存在了。此外，鯊魚曾經(jīng)歷過五次大規(guī)模的物種滅絕，其中一次約有96%的海洋生物滅絕。

Shark pregnancies can last longer than 3 years.

鯊魚的孕期可以持續(xù)三年以上。

Reproduction patterns in sharks vary. On average， sharks give birth after 11 or 12 months of pregnancy， but some sharks， such as the frilled shark can be pregnant for over three years.

Some sharks， like bull sharks， give live birth， while other sharks， like cat sharks， lay eggs. Long pregnancy terms， and the fact that some sharks take 10 to 12 years to reach sexual maturity， like the great white， further impact populations.

鯊魚的繁殖方式各不相同。平均而言，鯊魚在懷孕十一二個月后分娩，但有些鯊魚，如皺鰓鯊，可以懷孕3年以上之久。

一些鯊魚，如灰牛鯊，是胎生；而其他鯊魚，如貓鯊，是卵生。長孕期，以及一些鯊魚（如大白鯊）需要10至12年才能達到性成熟的事實更深層次地影響其數(shù)量。

Sharks do not vocalize.

鯊魚不會發(fā)聲。

Sharks are primarily silent creatures， as they don’t have organs for producing sound. Instead of speaking， sharks communicate through body language， such as zigzagging， shaking and moving their jaws.

鯊魚天生是沉默的生物，因為它們沒有發(fā)聲的器官。鯊魚不發(fā)聲，而是通過肢體語言進行交流，如游之字形、晃動下頜等。

Sharks can sense electricity.

鯊魚可以感應電流。

Sharks have a sixth sense — they can pick up nanoscopic electromagnetic currents. This extra sense can help them navigate the ocean and find prey， or even a mate.

“The minute electrical impulse that a prey’s brain sends to its heart to tell it to beat can be sensed by sharks， so they can find hidden prey quite effectively，” Macdonald said. With this extraordinary sense， sharks hunt sick and weak animals， playing a crucial role in keeping the marine ecosystem healthy.

鯊魚有第六感——它們可以感知納米級的電磁電流。這種額外的感知可以幫助它們在海洋中找到方向和獵物，甚至是配偶。

麥克唐納說：“鯊魚可以感知到獵物大腦發(fā)送到心臟以使其跳動的微小電脈沖，因此它們可以非常有效地找到隱藏的獵物?！睉{借這種敏銳的感知，鯊魚捕食患病和虛弱的動物，在保持海洋生態(tài)系統(tǒng)平衡方面發(fā)揮著至關重要的作用。