the amazing amazon , the widest , wettest and , so national geographic now affirms , the longest river in the world -lrb- 4,007 miles , 51 longer than the nile -rrb- , boasts the longest snake , the most venomous viper , the biggest rat , beetle and ant , along with razor-toothed piranhas that can reduce a brahman steer to raw bones in minutes and electric eels delivering 640 volts , enough to drive a metro - north commuter train .