对于圭亚那地区的海豚来说，只比其他动物多一种感觉还不够。除了回声定位能力以外，他们还能感觉到所捕食猎物的电场——这在真正的哺乳动物中还是第一次发现。相关论文发表于英国《皇家学会学报B》（Proceedings of the Royal Society B）。
德国罗斯托克大学的沃尔夫·汉克及其同事对热成像中所显现的圭亚那海豚上颌凹陷处密集的生理活动感到好奇。鱼类、有些两栖类以及像鸭嘴兽那种原始产蛋哺乳类动物，都会利用类似的凹陷处来捕捉附近动物产生的电场。
通过研究死亡海豚的结构，并训练一只活海豚对一个相当于鱼类产生的电场做出回应，研究小组发现，这些海豚也具有电场的觉察能力。
汉克表示：“电感知能力有利于在近距离内感觉到猎物的存在，因为此时回声定位感已不那么灵敏。”他认为，其他种类的海豚，甚至包括鲸，或许也有类似的天赋。他说：“绝大多数人都没有意识到鲸类也在海底捕食，因此，很可能它们采用的也是电场感应。”
汉克指出，电场感应器官是从古动物身上的须演变而来的。动物的这种机械性刺激感受器官，诸如人类耳朵里的毛细胞，能够机械性地发出触觉波或声波的激源。圭亚那地区海豚的这种感官适应性调节相当新奇，他怀疑“这种能力相对较容易演变，而且容易将机械性刺激感受器官演变为电场感受器”。
的确，这一研究结果表明，几乎所有的哺乳动物都有可能具有这种演变能力。（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.
