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水生世界的罗宾汉—射水鱼
2015年07月23日 趣味生物 评论数 1 ⁄ 被围观 784+


射水鱼是水生世界的罗宾汉——它们很少会错失自己的目标。然而,不同于罗宾汉,射水鱼在分享战利品时并没有那么热心。

射水鱼通过向猎物射出水柱捕食。它们和数量更多的、被称为箴鱼的鱼类共享水域。箴鱼捕捉的猎物和射水鱼相同,通常是蛴螬、蟋蟀或甲虫,并且如果有机会的话,会抢夺射水鱼击落的昆虫。

为了生存,射水鱼不得不进化出更加敏捷的捕猎新技能,比如“预先启动”。猎物仍在降落时,它们就会启动,扑向猎物将要击中的水面。不过,尽管这帮助射水鱼在白天打败了箴鱼,但它们不得不在箴鱼大显身手的夜晚放弃狩猎。

这种射水鱼和箴鱼之间的“军备竞赛”是通过分析在泰国红树林栖息地和实验室里对行动中的射水鱼进行的上百次高速摄影记录后发现的。

“在每个地方,射水鱼都被发现和其他在水面觅食的鱼类生活在一起。通常,这些竞争对手不仅在数量上超过射水鱼,还以相同的猎物为食。”来自德国拜罗伊特大学的Stefan Schuster表示,因此对射水鱼来说,保护好它们的猎物变得愈发具有挑战性。

Schuster及其同事在试验中发现了这一点。他们故意把食物丢到水中,然后拍下抢夺的视频。“在几乎所有情形下,射水鱼都能快速注意到正在降落猎物的初始速度和方向,并径直扑向其要降落的地点,从而极其高效地捕捉到食物。”Schuster介绍说。平均而言,射水鱼只用了90毫秒便到达食物处,而箴鱼用了253毫秒。

“我们的研究显示,同其他物种的竞争能扮演重要角色,迫使动物进入只有通过认知能力上的投资才能获得的新市场。”Schuster表示。(闫洁)

《中国科学报》 (2015-07-22 第2版 国际)

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英国新科学家网站相关报道(英文)

Archerfish up their game to outgun rivals stealing their catch

An archerfish demonstrates its impressive shooting and retrieval skills (Image: Ingo Rischawy/Michael Blum/Stefan Schuster)

Archerfish are the Robin Hoods of the aquatic world – they rarely miss their target. But unlike Robin Hood, they are less keen to share their loot.

Archerfish catch food by firing jets of water at prey. They share waters with more numerous fish called halfbeaks, which are after the same prey – typically grubs, crickets or beetles – and will snatch insects downed by archerfish if given a chance.

To survive, archerfish have had to evolve new, sharper hunting skills such as “predictive start”, whereby they launch themselves towards where the prey will hit the water while it is still falling. But although this helps them to beat halfbeaks during the day, archerfish have had to give up hunting at night, when halfbeaks’ skills come to the fore.

The discovery of this “arms race” between archerfish and halfbeaks was made by analysing hundreds of high-speed video recordings of archerfish in action, both in their mangrove habitat in Thailand and in the lab.

“At every spot, archerfish were found together with other surface-feeding fish, and typically these rivals not only outnumbered the archerfish, but also fed on the same prey that archerfish would down with their shots,” says Stefan Schuster of the University of Bayreuth in Germany, whose team conducted the research. “So it has become challenging for the archerfish to secure their prey.”

Specialist equipment
As part of the arms race, both species have developed specialisations to give them an edge.
Halfbeaks have evolved superior machinery for locating and snaffling prey in the dark, which seems to have driven archerfish to abandon hunting at night.

Lab analyses of skin from both species showed that compared with archerfish, halfbeaks have around five times more neuromasts on their backs – these are sensory cells that are vital for detecting waves triggered by prey landing on the water surface above.

Archerfish up their game to outgun rivals stealing their catch
Archerfish are keen-eyed killers (Image: Kim Taylor/naturepl.com)

In lab tests, archerfish did hunt at night in the absence of halfbeaks. They spotted potential prey in near total darkness, hitting and knocking it into the water almost every time.

But they struggled to locate the prey after they had knocked it into the water, taking much longer than halfbeaks do.

To make up for forsaking midnight snacks, archerfish have evolved superior visual skills that enable them to anticipate where “shot” prey will fall. During the daytime, this enables them to outpace their rivals to the spot where the unlucky insect falls.

“The halfbeaks show visual skills too, but they’re far less efficient than the archerfish,” says Schuster. “Archerfish win when they can use vision, but halfbeaks win in the dark.”

Food fight
Schuster and his colleagues discovered this in experiments where they deliberately tipped food into the water and then videoed the scramble.

“Archerfish were extremely efficient at making the catch in almost all cases by quickly noticing the initial speed and direction of the falling prey and heading right to the point where it would drop,” says Schuster.

On average, it took the archerfish just 90 milliseconds to get there, compared with 253 milliseconds for the halfbeaks.

“Our study shows that competition with other species can play an important role, forcing animals into new niches only available through cognitive investments,” says Schuster.

“Between-species competition appears to be driving the evolution and refinement of highly sophisticated behaviours in ways few would have predicted,” says Aaron Corcoran of Wake Forest University in Winston-Salem, North Carolina. “It’s remarkable that a fish species, the halfbeak, has apparently evolved specialised mechanical and visual sensing abilities to steal food from another fish species.”

Journal reference: Current Biology, DOI: 10.1016/j.cub.2015.06.005



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