NEW SCIENTIST (London, UK) 05 March 05 Turning salamander larvae into killing machines
The right vibrations transform a meek salamander larva into a killing machine. The "predator" morph, with its larger head and aggressive attitude, is better adapted to grabbing larger prey.
Visual, chemical or sound signals can trigger striking morphological changes in a range of aquatic animals and amphibians. For example, in the presence of the salamander Hynobius retardatus, tadpoles of the frog Rana pirica transform into fatter forms that are too big for the predator to grab.
Now Hirofumi Michimae of Hokkaido University in Japan and his team have found a counter-adaptation in the predator that is triggered by the vibrations of the tadpoles' tails. The shape-shifting salamander larvae develop into either "standard" or "predator" morphs, with longer, more substantial bodies and heads about a third broader. "The specific morphology and aggressive behaviour of the [predator] morph are advantageous for the consumption of large prey," says Michimae. It is the first time vibrations have been shown to cause a morphological transformation.
When the team reared the salamanders with tadpoles that had had their tails removed, they were half as likely to change into the predator morph. What's more, they found that artificial fins flapping like tadpole tails were about as effective as real tadpoles at inducing the larger morph, confirming that mechanical rather than chemical cues are the main trigger (Biology Letters, DOI: 10.1098/rsbl.2004.0242).
Turning salamander larvae into killing machines