Scientists make good ants go bad

Professor Simon Robson, Head of Terrestrial Ecosystems at JCU, examined Australian weaver ants, Oecophylla smaragdina, in collaboration with colleagues at Boston University in the United States.

The weaver ants’ colonies can contain over one hundred nests and more than half a million ants. The bigger ants, known as major workers, have a length of 8 to 10 millimetres; minor workers are half that size. The aggressive major workers act as soldiers and foragers, and expand the colony. The more placid minor workers care for larvae.

The scientists modified levels of the neurotransmitter, octopamine within the larger and smaller ants’ brains while keeping every other factor constant, in order to demonstrate a causal relationship between brain chemistry and behaviour.

Professor Robson said it had a remarkable effect. “The soldier ants became less aggressive and behaved like workers, and the workers became aggressive and behaved like soldiers,” he said.

Amazingly, the researchers also dissected ant brains to confirm the relationship between octopamine and aggression. It helps “not to drink a lot of coffee” before these fine-scale dissections, said Professor Robson.

He said the neurotransmitter octopamine was one of five chemicals originally suspected of playing a role in ant aggressiveness and its central role had now been confirmed.

“The unique ants of tropical Australia represent a valuable study system and it’s not surprising that researchers from the US would come here to study them.  The need to understand the modulation of aggression seems to be growing, and this research helps us understand how such behaviours evolve and are regulated in a variety of biological systems.”

Paper: Kamhi JF, Nunn K, Robson S, Traniello JFA (2015) Polymorphism and division of labour in a socially complex ant: neuromodulation of aggression in the Australian weaver ant, Oecophylla smaragdina. Proceedings of the Royal Society B: Biological Sciences 282:20150704

Link: To paper and pics - http://bit.ly/1SQFsYV

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