巴西生物学家用一种笨办法发现了世界上第一只会“注射”毒液的毒蛙。来自巴西圣保罗的布坦坦研究院的Carlos Jared在靠近巴西西南海岸的Goytacazes国家森林的丛林里进行野外考察的时候意外捡起了一只巴西雨蛙格林胄蛙(Corythomantis greeningi，如图)——一种小型、背部多疣状突起的绿色两栖类动物。这只蛙用隐藏在其上唇的刺划了Jared的手，他扔下这只蛙，之后他手臂上的剧痛折磨了他五个小时。其它有几种蛙物种也是有毒的，但至今在它们中间并没有一种被证明会喷射毒液，即将毒素“注射”入宿主的身体。新发现的毒蛙的毒液是致命的蝮蛇的两倍，研究人员今天在《当代生物学》网络版上报告了这一发现。该研究小组还在Goytacazes国家森林里发现了另一种有毒的巴西雨蛙，布鲁诺盔头蛙(Aparasphenodon brunoi)。它的毒液的毒性比蝮蛇要高出25倍，但这次研究人员很聪明，他们没有把它捡起来。这两种毒蛙都是通过皮肤的毒腺中所含的头刺刺中对方而使其中毒。当它们发动攻击时，它们的皮肤会收紧，满覆毒液的刺就从毒蛙的嘴唇里伸出来。研究人员设想，当一个饥饿的捕食者将嘴靠近毒蛙时，毒蛙就会开始摇晃头部，猛刺每一个它的脸能伸进的角落。这两种毒蛙并没有很近的亲缘关系，因此研究人员认为还会有几种蛙可能也演化成了毒蛙。在危机四伏的热带雨林里，这种适应过程可能经历了多次的演化，只是科学家们从来没有注意到而已。
原文链接：
Amid agony, scientists discover world’s first venomous frog
原文摘要：
Brazilian biologists have discovered the world’s first venomous frog the hard way. When Carlos Jared of the Butantan Institute in São Paulo, Brazil, picked up a Brazilian hylid frog (Corythomantis greening, pictured)—a small, lumpy, green amphibian—while doing fieldwork in a jungle in the Goytacazes National Forest near the southwest coast of Brazil, the frog raked the spines hidden within its upper lip across his hand. He dropped the frog, and excruciating pain shot up his arm for the next 5 hours. Several other species of frogs are poisonous, but until now none have been shown to be venomous—that is injecting a toxin into their host. C. greening’svenom is twice as potent as that of the deadly pit viper, the researchers report online today inCurrent Biology. The team found another venomous Brazilian hylid frog, Aparasphenodon brunoi, also in the Goytacazes National Forest. Its venom was a whopping 25 times more deadly than that of a pit viper, but this time the researchers were smart—they didn’t pick it up. Both frogs deliver their venom from head spines resting in toxic glands in their skin. When the animals attack, the skin contracts and the poison-coated spines protrude from the frog’s lip. Researchers imagine as a hungry predator closes its mouth over the frog, it begins shaking its head and jabbing the spines into every corner a frog’s face can fit. These two frog species are not very closely related, so researchers think several more frogs could have evolved to be venomous. It’s possible the adaptation evolved multiple times in the perilous rainforests, but scientists just never picked up on it.
