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小老鼠为了求爱也是要唱情歌的
2015年09月21日 科学研究 评论数 1 ⁄ 被围观 525+


老鼠是如何求爱?如何吸引异性?一项最新的研究发现,它们通过唱“老鼠情歌”,追求伴侣,这为位数极少的会唱歌的哺乳动物――鲸类、蝙蝠和人类的名单上又增加了一名新成员。

雄性老鼠嗅到雌性老鼠的气味,会发出超声波的尖叫,美国科学家已经将这些叫声录了音。这是科学家首次证明老鼠的叫声不是它们随意发出的声音,其实是可以识别的歌曲
,把唱歌作为一种求爱仪式在动物王国很常见,尤其是鸟类、昆虫和两栖类动物如蛙类,喜欢用动听的声音吸引异性,但在哺乳动物中,这种求爱方式并不常见。在此之前,科学家知道,除人类之外,还有蝙蝠和鲸类等海洋哺乳动物,比如鲸和海豚的用歌声求爱。

密苏里州圣路易斯的华盛顿大学的一个研究小组的这一新发现显示,老鼠也是低音歌手,因为它们发出的这些声音,人是听不到的。然而,为了让人能够听到这些声音,研究人员对“老鼠情歌”进行了技术处理,去除时序的干扰,降低定音,于是,产生出一种吱吱的尖叫声,听起来很象鸟叫。

该项研究的主要人员蒂莫西·豪莱说,老鼠的曲调符合构成歌曲的基本要素,而不是无规则的发音模式。他说:“在学术界,对于什么样的声音才能被称作歌曲这个问题有不同的说法,但是通常有两点是必须具有的,一是应该有一些可识别的音节差异,也就是声音可分成几类,而不是只有一个音在不断地重复。第二是应该有一定的规律性,比如,有多次出现的主旋律。”

研究人员认为,“老鼠情歌”的丰富性和多样性似乎达到了许多鸟类鸣叫的水平。但老鼠并不象鸟类那样善于唱歌,在主旋律方面也没有鸟类老练和自信。豪莱博士说:“鸟类在求爱期间唱歌,是向对方传递自己所具有的优势等信息,但老鼠是否也通过唱歌传递这样的信息,目前还不清楚。”

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Using a sophisticated array of microphones and a sound chamber he developed, a University of Delaware researcher discovered the world is full of tiny furry Beyoncés. Studying all the Single Ladies' communication provides insight into brain mechanics.
Credit: Jeff Chase, University of Delaware

They don't use gondolas or croon like Sinatra. But scientists have known for a long time that male mice belt out something like love songs to females when the time seems right to them.

What they didn't know -- until a University of Delaware researcher developed a sophisticated array of microphones and a sound analysis chamber -- was that female mice were singing back.

No one knows if the females are singing "It Had To Be You" or "Catch Me If You Can," but mouse "songs" -- as neuroscientist Joshua Neunuebel, assistant professor of psychological and brain sciences, calls them -- apparently are quite the thing with these little rodents.

You can't tell that a mouse is singing or shouting. There is no obvious physical sign. And their voices during these interactions register in a range far beyond the reach of human ears, Neunuebel said.

The highest range the human ear can detect is about 20 kilohertz. The high-pitched voice of a mouse registers at about 35 to 125 kilohertz, he said.

It takes special microphones to pick that up and Neunuebel and his collaborators have worked on collecting, analyzing and interpreting all sorts of mouse sounds and related data.

Neunuebel developed a sound system and analysis equations that allowed researchers to figure out -- with up to 97 percent accuracy -- which sound came from which mouse.

That's when they discovered that female mice weren't just listening to male voices. They were singing back.

With the new sound analysis capacity -- and especially the ability to pinpoint which mouse the vocals are coming from -- a platform for much broader research now is available.

The work could lead to advances in understanding autism, for example, and deficits that may exist in the neural circuits of the brain that underlie social communication, Neunuebel said.

Studying mouse communication and behavior can produce great insight into brain mechanics and systems and possibly give researchers valuable insight into how human brains work.

"We are just scratching the surface," he said.

Neunuebel collaborated with three former colleagues at the Janelia Research Campus of the Howard Hughes Medical Institute -- Adam Taylor, Ben Arthur and S.E. Roian Egnor.

It has been known for some time that male mice vocalize during their efforts to find a mate. Neunuebel now has demonstrated that the source of mouse songs can be pinpointed to specific mice and as part of that work subsequently demonstrated that female mice were in the vocal mix, too.

The system gathered data as four mice -- two males, two females -- were observed interacting and often detected vocal exchanges during chases when a male pursued a female. The data showed that females who responded vocally to a male's "song" also slowed down, making it easier for the male to catch up to them. Unresponsive females kept up their pace.

That makes researchers think these songs may be communicating important social information -- but that is another study, yet to come.

To get this data, Neunuebel and his collaborators developed a fascinating system. They rigged up an acoustically precise chamber, surrounded by foam, that had nylon mesh walls to reduce "reflections" -- the phenomenon of sound bouncing around an enclosed space and off walls. They installed an array of four microphones, illuminated the chamber with infrared light, and linked each mouse to a tracking system.

They developed a calculation to divide the sound into smaller pieces and then estimated the source location for all the small pieces, correcting for delays caused by the speed of sound in air at room temperature and at standard atmospheric pressure.

They developed a theoretical grid across the floor of the chamber, spaced at a quarter of a millimeter. From each point on the grid, they calculated the estimated delay between each possible pair of microphones and used this to analyze sounds and estimate their sources.

With all of that, they produced Mouse Ultrasonic Source Estimation (MUSE) software, now available for download.

Neunuebel's new lab at UD is looking at social communication in mouse models of autism. These mice spend 12 hours in the chamber, which is equipped with food, water and bedding, and half a terrabyte of data is collected in each 12-hour period. To analyze that much material, Neunuebel, in his ongoing work, is taking advantage of the Farber High-Performance Computing Cluster, which speeds the analytics dramatically.

"That has been incredibly helpful," he said. What would have taken weeks can now be done in less than a day.

"The University has put the pieces in place to make this happen," he said.

Neunuebel earned his doctorate in neuroscience at the University of Texas Health Science Center at Houston and a postdoctoral fellowship at Howard Hughes Medical Institute at Janelia Research Campus.

The work was supported by the Howard Hughes Medical Institute and published by eLIFE sciences.


Story Source:

The above post is reprinted from materials provided by University of Delaware. The original item was written by Beth Miller. Note: Materials may be edited for content and length.


Journal Reference:

  1. Joshua P Neunuebel, Adam L Taylor, Ben J Arthur, SE Roian Egnor.Female mice ultrasonically interact with males during courtship displays. eLife, 2015; 4 DOI: 10.7554/eLife.06203


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