August 5, 2009-Just as Hercules had the multi-headed hydra to contend with, ocean predators tussle with two-headed sea snakes-or so it appears. Some sea snake species, such as Hydrophis pachycercos (pictured), have evolved so that sharks and other predators can't tell whether the serpents are coming or going, Johan Elmberg and Arne Rasmussen report in a new study today in the journal Marine Ecology.

When Rasmussen on a research dive in Indonesia, said Elmberg, who was not on the dive, "he saw a venomous sea snake go head first into a narrow crevice. Then suddenly he was surprised to see the snake pull its head out, as if the snake had been able to very quickly turn around inside the crevice."
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