Abstract
The asymmetric mandibles of termites are hypothetically more efficient, rapid, and powerful than the symmetric mandibles of snap-jaw ants or termites. We investigated the velocity, force, precision, and defensive performance of the asymmetric mandibular snaps of a termite species, Pericapritermes nitobei. Ultrahigh-speed recordings of termites revealed a new record in biological movement, with a peak linear velocity of 89.7–132.4 m/s within 8.68 μs after snapping, which caused an impact force of 105.8–156.2 mN. High-speed video recordings of ball-strike experiments on termites were analysed using the principle of energy conservation; the left mandibles precisely hit metal balls at the left-to-front side with a maximum linear velocity of 80.3 ± 15.9 m/s (44.0–107.7 m/s) and an impact force of 94.7 ± 18.8 mN (51.9–127.1 mN). In experimental fights between termites and ant predators, Pe. nitobei killed 90–100% of the generalist ants with a single snap and was less likely to harm specialist ponerine ants. Compared with other forms, the asymmetric snapping mandibles of Pe. nitobei required less elastic energy to achieve high velocity. Moreover, the ability of P. nitobei to strike its target at the front side is advantageous for defence in tunnels.
Highlights
Some invertebrates’ elastic power-amplifying systems that incorporate latches and springs can overcome the physiological limits of muscle contraction and perform a powerful or rapid movement[1,2]
In the high- and ultrahigh-speed recordings, the mandible-snapping behaviour of Pe. nitobei soldiers began with the right mandible pressed against the left mandible to store elastic energy
The termites required 261.3 ± 43.1 ms (n = 10) to complete the loading phase: During the first 213.8 ± 43.5 ms, both antennae extended forward as the right mandible continued to press against the left mandible; it took another 47.5 ± 22.5 ms to turn their antennae towards their rear before snap
Summary
Some invertebrates’ elastic power-amplifying systems that incorporate latches and springs can overcome the physiological limits of muscle contraction and perform a powerful or rapid movement[1,2]. Asymmetric snapping mandibles may perform more violent strikes than symmetric mandibles can by storing elastic energy in the left twisted mandible[12]. Termites can snap the ground to leap away from ants[17,18] or snap at ants to push them away[16] or even kill them[6] These defensive behaviours have not been studied in termites with asymmetric mandibles. We conducted ultrahigh- and high-speed video recordings, ball-strike experiments, and ant-defence assessments to test the following hypotheses: (1) snaps of asymmetric mandibles are more rapid and powerful than snaps of symmetric mandibles are, (2) asymmetric mandibles can precisely strike at the front side, and (3) asymmetric mandibles are effective for defending against ants. In addition to revealing the fastest known animal movement, we compared asymmetric and symmetric termite mandibles and analysed the evolution and mechanical effects of mandible morphology
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