對于圭亞那地區(qū)的海豚來說,，只比其他動(dòng)物多一種感覺還不夠。除了回聲定位能力以外,，他們還能感覺到所捕食獵物的電場——這在真正的哺乳動(dòng)物中還是第一次發(fā)現(xiàn),。相關(guān)論文發(fā)表于英國《皇家學(xué)會(huì)學(xué)報(bào)B》（Proceedings of the Royal Society B）。
德國羅斯托克大學(xué)的沃爾夫·漢克及其同事對熱成像中所顯現(xiàn)的圭亞那海豚上頜凹陷處密集的生理活動(dòng)感到好奇,。魚類,、有些兩棲類以及像鴨嘴獸那種原始產(chǎn)蛋哺乳類動(dòng)物，都會(huì)利用類似的凹陷處來捕捉附近動(dòng)物產(chǎn)生的電場,。
通過研究死亡海豚的結(jié)構(gòu),，并訓(xùn)練一只活海豚對一個(gè)相當(dāng)于魚類產(chǎn)生的電場做出回應(yīng),，研究小組發(fā)現(xiàn)，這些海豚也具有電場的覺察能力,。
漢克表示：“電感知能力有利于在近距離內(nèi)感覺到獵物的存在,，因?yàn)榇藭r(shí)回聲定位感已不那么靈敏。”他認(rèn)為,，其他種類的海豚,，甚至包括鯨，或許也有類似的天賦,。他說：“絕大多數(shù)人都沒有意識(shí)到鯨類也在海底捕食,，因此，很可能它們采用的也是電場感應(yīng),。”
漢克指出,，電場感應(yīng)器官是從古動(dòng)物身上的須演變而來的。動(dòng)物的這種機(jī)械性刺激感受器官,，諸如人類耳朵里的毛細(xì)胞,，能夠機(jī)械性地發(fā)出觸覺波或聲波的激源。圭亞那地區(qū)海豚的這種感官適應(yīng)性調(diào)節(jié)相當(dāng)新奇,，他懷疑“這種能力相對較容易演變,，而且容易將機(jī)械性刺激感受器官演變?yōu)殡妶龈惺芷?rdquo;。
的確,，這一研究結(jié)果表明，幾乎所有的哺乳動(dòng)物都有可能具有這種演變能力,。（生物谷 Bioon.com）
doi:10.1098/rspb.2011.1127
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Electroreception in the Guiana dolphin (Sotalia guianensis)
Czech-Damal, Nicole U.; Liebschner, Alexander; Miersch, Lars; Klauer, Gertrud; Hanke, Frederike D.; Marshall, Christopher; Dehnhardt, Guido; Hanke, Wolf
Passive electroreception is a widespread sense in fishes and amphibians, but in mammals this sensory ability has previouslyonly been shown in monotremes. While the electroreceptors in fish and amphibians evolved from mechanosensory lateral lineorgans, those of monotremes are based on cutaneous glands innervated by trigeminal nerves. Electroreceptors evolved from otherstructures or in other taxa were unknown to date. Here we show that the hairless vibrissal crypts on the rostrum of the Guianadolphin (Sotalia guianensis), structures originally associated with the mammalian whiskers, serve as electroreceptors. Histological investigations revealedthat the vibrissal crypts possess a well-innervated ampullary structure reminiscent of ampullary electroreceptors in otherspecies. Psychophysical experiments with a male Guiana dolphin determined a sensory detection threshold for weak electricfields of 4.6 µV cm?1, which is comparable to the sensitivity of electroreceptors in platypuses. Our results show that electroreceptors can evolvefrom a mechanosensory organ that nearly all mammals possess and suggest the discovery of this kind of electroreception inmore species, especially those with an aquatic or semi-aquatic lifestyle.
