Patek, S.N., Baio, J.E., Fisher, B.L., Suarez, A.V., 2006. Multifunctionality and mechanical origins: Ballistic jaw propulsion in trap-jaw ants. Proceedings of National Academy of Science 103, 12787-12792.

If a Swiss army knife is in your camping gear, think again. An apparatus with many functions could be disadvantageous in the biological world, because costs of having many functions will not let every specialized part of the apparatus evolve toward an ultimate design. Nevertheless, multifunctionality is common. The trick seems to be tradeoff between functions for the greatest sum of benefits. But important questions remain: can a multifunctional apparatus be highly competitive in each function, and, if so, how?

The authors' crucial finding is that mandibles of the trap jaw ants Odontomachus rank among the fastest animal apparatus and simultaneously perform different functions. High-speed imaging revealed their unparalleled jaw movements with the peak velocity from 35 to 64 ms-1, 0.13 ms mean duration, and the acceleration at the order of 105_g: faster than the mantis shrimp strike, the cnidarian nematocyst stylets, or the fungal ballistspore launch. The mandibles deliver rapid bites for prey capture, and also exert enough force - 300 times the ant's weight - to propel the body into the air by strikig the substrate.

With this ballistic launch, the ants escape from predators and defend against conspecific intruders. In the behavior called bouncer defense, the strike pops both the intruder and the ant into the air. Odontomachus's multifunctional mandibles undoubtedly work out one of the fastest mechanics among animals. Because many functions depend on this mandible snap, the evolution of the mandibles somewhat bypassed the tradeoff, making such extreme kinematics evolutionarily affordable.

(250 words)

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(posted Mar. 24 2009)