Ant weightlifting

Ant weightlifting

This image is an Asian weaver ant holding 500mg in its mandibles. That is ~100x the weight of the ant.

This picture was taken by Dr Thomas Endlein of Cambridge University as part of research on the adhesive properties of insects’ feet.

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Like a bear trap

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Photo credit: Alex Wild (myrmecos.net)

Strange and oddly shaped mouth parts a certainly not rare in the animal kingdom and ants have their share of strangely appearing mouth parts as well. One species which undoubtedly breaks a record is the trap-jaw ant Odontomachus bauri. Named after its jaws, which close like a snap, this ant species has one of the fastest predator strikes currently known in the animal kingdom. Dr. Sheila Patek and her colleagues have clocked the movement of the closing mandibles with 35 to 64 meters per second (78 to 145 miles per hour), which means the time it takes the ant to strike is a mere 0.13 milliseconds (that is about 2,300 times faster than the blink of an eye) and each jaw generating forces exceeding 300 times the insect’s body weight.

Trap jaw-ants use their jaws to capture prey, eject intruders or, more oddly, “jump” to safety when threatened by striking their jaws against the ground to propel themselves into the air. These “jumps” cast the ants up to heights of 6.1 to 8.3 centimeters, but only 3.1 centimeters horizontally, which is enough to confuse enemies and escape. The full research article of Dr. Patek’s study has been published in PNAS.

‘Supersoldier’ ants

Photo credit: Alex Wilde (myrmecos.net)

Ant colonies are organized in different castes which fulfil diverse functions like workers and soldiers. Dr Ehab Abouheif and his colleagues has shown that in Pheidole ants, monstrous ‘supersoldiers’ with huge heads and jaws can be created by activating ancient genes. Caste affiliation is determined by temperature, nutrition and the juvenile hormone levels inside the egg during development, therefore ‘supersoldier’ development can be induced in many different species, if treated with the hormone at the right time. Naturally this caste is very rare and can only be found in eight species in Mexico where they help protecting the colony by blocking entrances from invaders with their oversized heads, however the fact that these ‘supersoldiers’ can be induced in different Pheidole species is evidence that a common ancestor of them possessed this trait and that the developmental pathway is retained in all species, but shut down in most. This study has been published in Science.

Slaves rebel against masters

Photo Credit: Alexandra Achenbach

Ants of the species Temnothorax longispinosus have been shown to launch effective rebellions against their oppressors. Protomognathus americanus, a social parasitic ant found in the north eastern United States, regularly raids nests of neighbouring species, killing adult ants and abducting the young. The now enslaved ants are forced to gather food, defend the nest and care for larvae of the slavemakers. However T. longispinosus workers eventually start killing pupae of their slaveholders, which leads to reduced growth of the social parasites’ nests and fewer raids on neighbouring related host colonies. Usually, P. americanus pupae have an 85 percent chance of survival, but it has been shown that this rate drops to a range of 58 to 27 percent when enslaved ant workers care for the offspring.  This study was published in Evolutionary Ecology.

Fungus turns ants into zombies

Photo Credit: Dr. David Hughes

Some parasite species have evolved mechanisms to alter their hosts’ mind and control its actions, often co-opting a pre-existing behaviour to its benefits. Although not truly undead in a classical definition of “zombie”, worker ants of the tribe Camponotini (Formicinae: Formicidae) have been found to be under the control of a fungus (Ophiocordyceps unilateralis ) which leaves them no other choice but to follow its commands. Carpenter ants mostly nest high in the canopy of tropical forests in Africa, Australia, Brazil and Thailand. When workers trek down to the forest floor to forage, the fungus attaches itself to them and uses enzymes to break down their exoskeleton to enter the body. Once infected, the fungus uses as-yet unidentified chemicals to direct the ant to leave its hive and take it to a place with the optimal height from the ground, prevalent temperature, humidity and orientation of the leaves, where the ant bites in the underside of a leave and dies. The fungus carries on to grow after the ants’ death, producing a long stem that protrudes from the ant’s head, shooting spores out, while at the same time preserving and reinforcing the ants’ exoskeleton to protect itself. Due to the destructive nature of the fungus which is capable of destroying entire colonies, ants have evolved an ability to detect infected members and will carry away diseased ants in order to contain the exposure to fungal spores. The research of Dr. David Hughes and his colleagues is available online on PLoS ONE.