Termite’s Twisted Mandible Presents Fast, Powerful, and Precise Strikes

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-tofront 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. 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. For example, mantis shrimps (Crustacea: Stomatopoda) perform high-speed strikes to prey by using elastic energy stored in their raptorial appendages 3. Springtails (Hexapoda: Collembola) escape from enemies with quick and powerful jumps by using their springing organ 4. Many ants and termites, such as the snap-jaw ant Mystrium camillae Emery (Hymenoptera: Formicidae) 5 and the soldiers of termite Termes panamaensis (Snyder) (Blattodea: Termitidae) 6 , have mandibles that are morphologically specialised for powerful snapping attacks. The snapping speeds of the mandibular attacks of M. camillae (111.1 m/s) 5 and T. panamaensis (67 m/s) 6 are the most rapid animal movements currently reported 1,5,6 , followed by the mandible-closing movement of Odontomachus bauri Emery trap-jaw ants (64.3 m/s) 7 , the diving of gyrfalcons (58 m/s) 8 , the nematocyst discharge of jellyfish (37 m/s) 9 , and strike behaviour of mantis shrimps (31 m/s) 1. The snapping mandibles of termite soldiers have two forms: symmetric and asymmetric 10,11. T. panamaensis has two narrow and elongated symmetric snapping mandibles that press together until they slide against each other (Fig. 1a). These mandibles strike enemies along their lateral sides 6. By contrast, the asymmetric snapping mandibles of some termites are relatively short and wide, with a twisted left mandible and curved right mandible 10. The right mandible presses against the left until the two surfaces slide. Moreover, the left mandible snaps in a clockwise motion (Fig. 1b), presumably striking enemies along the front side. Additionally, asymmetric sna...

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“…Some species have soldiers with vestigial mandibles, fully dependent on chemical secretion for defence [107]. On the opposite end of the spectrum, soldiers with symmetric or asymmetric snapping mandibles have evolved independently several times within Termitidae [146,147]. Finally, some lineages of Termitidae lost the soldier caste entirely and are exclusively defended by workers [148].…”

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“…Each mandible (Figure 4) bears an apical tooth and a variable number of marginal teeth, as well as a molar plate at the base (Figure 4). In general, the right mandible shows less modification than the left in the Rhinotermitidae and Hodotermitidae, whereas there is a less asymmetrical trend in the Termitidae (Jurgens et al, 2020;Kuan et al, 2020).…”

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“…The sticky toxic and irritating content of the frontal gland is sprayed at a distance from the nasus of the soldiers in Nasutitermitinae 47 . Other strategies are as peculiar as closing entrance holes with soldier heads (phragmosis) or strikes by modified symmetrical or asymmetrical snapping mandibles causing devastating wounds to invertebrates 34 , 41 , 54 , 55 . Defense is not restricted to soldiers, the defensive mechanism of workers in Neocapritermes taracua involves self-sacrifice through body rupture, allowing two separately stored secretions to come into contact together and to produce a sticky and toxic cocktail harmful to opponents 56 , 57 .…”