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專題報導 海洋
3 mins

10 個關於鯊魚有趣的真相

綿延不絕的牙齒?忍者?未出世就殘殺同類的小鯊?

作者: 綠色和平英國海洋專案主任 Willie Mackenzie
動畫裡那些形狀奇特的鯊魚可不是憑空想像的。關於鯊魚,除了長滿尖牙的大嘴,還有更多有趣的事實等你來了解。

鯊魚的牙齒從來不停止生長,牙列上一直不斷生長牙齒,這就是為什麼你很少看到鯊魚牙醫。

但是,鯊魚除了那些不討人喜歡的新聞外,令人吃驚的不僅僅是牙齒。濾食性鯊魚(像是巨口鯊)通常有巨大的口腔(通常無害);翼頭鯊的頭部就佔了它整個身長的 1/2;長尾鯊的大尾巴(通常在吃掉獵物之前,會先用大尾巴嚇嚇它們!)就和它的身體一樣長。

很多種類的鯊魚都是母鯊的皮較厚。母鯊魚的皮膚可以是雄鯊魚皮膚的兩倍厚,據說這是為了承受在交配過程中被雄鯊魚啃咬。

關於鯊魚的皮膚,這不是唯一一件令人吃驚的事。鯊魚皮是由數個細齒所組成,當你用不正確的方式摸它時,它會摸起來很粗糙;粗糙到可以當作砂紙使用。若從另一方向接觸它,你會感覺鯊魚皮膚是光滑而且水潤的。鯊魚皮也常常被用來做成實用品及裝飾品,像是忍者劍上的把柄。

世界上最大的鯊魚是鯨鯊,它是一種長 13.5 公尺的溫和食浮游生物巨鯊。但與大白鯊的史前時代祖先-巨齒鯊相比,鯨鯊就相形失色了。巨齒鯊的牙齒就有 6 吋,而且它的身長超過現今的雙層巴士車身,差不多就跟現在的抹香鯨一樣大。你應該慶幸我們在現代的水域裡(應該)不會再巧遇他們啦!

全世界最小的鯊魚是侏儒燈籠棘鮫,就像其他燈籠棘鮫一樣,侏儒燈籠棘鮫也會在黑暗的深海中發光。

鯊魚會用電波去找尋獵物,而且鎚頭鯊家族會用它們奇形怪狀的頭部來回掃動,就像生物性金屬探測器一樣找尋匿伏在海床的美食。連擅長攻擊的魟魚都是他們的獵物,即使是冒著生命危險仍要大口吃魟魚。

有些鯊魚產卵,有些則臨盆生小孩。就魚類來說,鯊魚生產的後代數量較少,因此它們在繁衍能力上屬於較弱勢的物種。在生產前鯊魚要懷孕兩年,比鯨魚或大象都還要長;有些種類的鯊魚一次只會生產一隻或兩隻小鯊魚,這些順利生出的小鯊魚還在媽媽子宮的時候,就會吃掉其他隻手足,爭取被生下來存活的機會。

“Jumping the Shark” 這個詞指的是有些事情跨越了理智線,進入了瘋狂的境界。
這個俚語源自於影集 Happy Days 中的主角 Fonz,就如同 Fonz 當時在有鯊魚的水池滑水跳過一尾鯊魚一樣瘋狂。鯊魚攻擊人的新聞得到了很多媒體關注,但事實上,人類每秒就殺死 3 隻鯊魚,一個禮拜就可以殺死 1,848,000 隻這麼多….

譯者:Sannie Lee

《原文附錄》

Sharks have a never-ending supply of teeth. They regenerate replacement dentition on an inexhaustible toothy conveyor belt... which explains why you see so few shark dentists.

But sharks are not all about teeth, despite the bad press. Filter feeders like the megamouth shark, are mostly big (but harmless) mouths; the winghead shark has a head half the length of its body, and; the thresher sharks have a huge tail (ideal for stunning fish before eating them) that can be the same length as its body.

In many shark species the females have much thicker skin (I know, I know...). It can be twice the thickness of the males' skin and is thought to be an adaptation to endure ferocious bites from the males during sex.

That's not the only remarkable thing about shark skin, which is composed of tiny teeth like scales called 'denticles' which make it rough if you stroke it the wrong way. So rough, in fact, that it used to be used as sandpaper. The advantage is that in the other direction it makes the shark sleek and hydrodynamic. Shark skin leather (called Shagreen) has also been used for practical and ornamental purposes – including on the handles of ninja swords!

The world's biggest shark is the whale shark, a peaceful plankton-munching giant that can be 13.5 metres long. But it was dwarfed by a prehistoric giant shark, Megalodon, which was a pumped up ancestor of today's great white. It had six inch teeth and was much, much bigger, easily overshooting a double-decker bus in length, and possibly about the same size as today's Sperm whales. Think yourselves lucky they are (probably) no longer around.

The world's smallest shark is probably the dwarf lanternshark, which, like other lanternsharks, glows in the dark.

Sharks use electrical senses to find prey, and the oddly-shaped heads of the hammerhead family are used sweep back and forth like a biological metal detector to find lunch lurking on the seabed.  They even enjoy munching on stingrays, oblivious to their deadly barbs.

Some sharks lay eggs and some give birth to live young. They usually have relatively few babies (in fish terms) which makes them vulnerable species.  Sharks can be pregnant for two whole years before they give birth, which is longer than whales or elephants. A few shark species give birth to just one or two 'pups' at a time, the successful offspring having eaten all their siblings inside the womb beforehand…

The phrase 'Jumping the Shark', meaning when something crossed the line into ridiculousness, originated on an episode of the sit-com Happy Days when lead character, the Fonz, inexplicably jumped over a shark on waterskis.

Shark attacks get lots of media attention, but humans kill an estimated 3 sharks every single second. Over Shark Week alone that will add up to some 1,848,000 sharks …