八爪魚有腳？科學家︰章魚有6臂2足

八爪魚有腳？科學家︰章魚有6臂2足

〔編譯陳成良／綜合報 導〕章魚（八爪魚）的英文「octopus」源自於古希臘，意為「八隻腳」。但泰晤士報十三日報導，科學家最近利用魔術方塊等玩具對章魚進行觀察實驗後認 定，章魚在水裡行進時，主要使用最後面兩隻觸手，而其餘六隻觸手只在捕食時派上用場，在行進時卻是閒置的。因此，從功能上來說，章魚的「八爪」有六隻實為 手臂，而另外兩隻則是腿。

研究發現章魚慣用後面兩隻觸手行進

主 持這項實驗的海洋生物專家利托女士表示，章魚要游泳時，先用後面兩隻觸手把身體往前推，再用另外六隻觸手讓自己往前游，在岩石或海床上活動時，也多半使用 後面兩隻觸手。此前，一般認為章魚八隻觸手具有兩種不同功能的分組，一組用來在水中推進，另一組則是像人類的手一樣，用來操控。

這項在歐洲二十處海洋生物館進行的研究，原本是要觀察章魚在活動或進食時，是否像人類有左右撇子之分，偏愛使用哪一側或哪隻觸手，抑或每隻觸手都可靈活運用。

研究人員是在分析二千多份觀察章魚的資料後，得出上述結論。在研究過程中，研究人員觀察到，當章魚被纏住時，也會使用從前面算起的第三對觸手來協助自己脫身，雖然頻率比使用前面兩對觸手來得少，但已超出研究人員的預期，所以這三對觸手都可稱之為「手臂」。

大 多數人習慣用右手，也有一部分人慣用左手，人們戲稱為「左撇子」，那麼章魚有那麼多隻觸手，牠們是否也有慣用的「手」呢？關於這一點，研究人員發現，章魚 並沒有特別偏愛使用左側或右側的觸手，章魚的眼睛角度朝前，會比較常使用在其視線範圍的觸手。至於先前有研究指稱，有的章魚慣用一側觸手，其中一個解釋 是，這些章魚可能有近視或視力障礙。

Source: http://www.libertytimes.com.tw/2008/new/aug/14/today-int4.htm

How many arms does an octopus have?

The answer is six: the other two are legs

Simon de Bruxelles

A giant Pacific octopus called Mavis has helped researchers to prove that the one thing everyone knows about the creatures is wrong.

The name octopus is derived from the Ancient Greek for eight feet. Mavis, who lives in a tank at Weymouth Sea Life Centre, actually has six arms and two legs.

Researchers who were studying octopuses' behaviour were taken aback to discover that some of the most basic assumptions about them were wrong.

Until now it had been believed that the tentacles were deployed in two equal sets, one set of four for propulsion and the other for manipulation.

The research, conducted at 20 centres across Europe, was originally intended to establish whether octopuses favoured one side over the other, as people do, or were multidextrous.

Toys including a Rubik's Cube were placed in the octopus tanks and a careful watch was made of which limbs the animal used to play with them.

Claire Little, who led the research at Weymouth, where the project was devised, said: "We've found that octopuses effectively have six arms and two legs. " It had been thought they used four tentacles for movement and the other four for feeding and manipulating objects, but observations showed that they use the rearmost two to get around over rocks and the seabed.

"They also use these two legs to push off when they wish to swim, and then other tentacles are used to propel them."

Mavis, whose head is the size of a dinner plate and whose limbs are about half a metre (20in) long, is a member of one of the largest species of octopus. Helped by the suckers on her tentacles she can easily prise open clams and mussels that would defeat most people.

The giant Pacific octopus can weigh up to 71kg (more than 11 stone) in the wild, although Mavis has some way to go. Ms Little said: "We haven't tried to take her out of the tank to weigh her because she'd find that quite traumatic."

Octopuses are among the most intelligent of marine creatures and can learn to open jam jars and manipulate small objects such as the Rubik's Cube - although, so far as is known, none has yet succeeded in solving the puzzle.

During the study, researchers discovered that when octopuses get in a tangle they use their third pair of arms to help. Ms Little said: "The real surprise was the frequency with which octopuses employed their third tentacles from the front on both sides.

Though it was markedly less than the front two pairs, it was more than we expected, given that earlier studies suggested the four rearmost limbs were reserved mainly for propulsion.

"More than half of the octopuses studied were found to display no bias at all for either right or left-sided limbs. The rest were split fairly evenly between those preferring the right side and those favouring the left.

"An octopus's eyes are angled towards the front of its body, so if it used its eyes to determine which tentacles it mobilised, you would expect the choice to favour those more directly in its line of view. That was precisely what we found."

Some previous studies had found that octupuses favoured one side over the other, and the explanation for this was that some were shortsighted or had visual impairments.

Ms Little said: "We identified seven octopuses that genuinely do prefer one side over the other, possibly because of some weakness in the other eye.

"If any of those animals should fall sick, we can now care for them that little bit more efficiently by delivering food and medication from the direction they prefer. As with any sickly animal, any measure that reduces stress, however slightly, can make a crucial difference," she said.

Researchers gathered the data from more than 2,000 separate observations, assisted by members of the public who were invited to take part in the study. The octopuses were mainly the common octopus, Octopus vulgaris, which also inhabits British waters.

A larger-scale study is now planned so that the findings can be published in a scientific journal.

Source: http://www.timesonline.co.uk/tol/news/environment/article4517779.ece