What may seem like a plot of a science fiction movie, is actually the scenario present in one little corner of our biological realm. To that end, entomologists are already aware of a unique natural phenomenon where groups of ants tend to abandon their fellow brethren, to protect a particular caterpillar (lycaenid butterfly variety) against its enemies. This occurrence was long believed to be a product of a reciprocal relationship – where both parties had something to gain from their actions. But now, researchers at the Kobe University in Japan have uncovered a more deeper biological aspect in this scope. According to them, the lycaenid caterpillar can secrete a special substance from its dorsal nectary organ. And when this substance is consumed by the ants, it basically turns them into ‘bodyguards’ who fight for the caterpillar instead.
Quite intriguingly, these ‘converted’ bodyguard ants were found to be not exactly willing in their guarding duties. In that regard, the scientists observed that the ants didn’t just consume the secretion and went their merry way. Instead they stuck around the caterpillar – thus hinting at a biological factor which is not just confined to a symbiotic relationship.
So, to make further tests, the researchers brought back both of the creature types to their laboratory. They divided up the ants into two separate groups, and one of these groups was allowed to feed on the secreted material from the caterpillar’s dorsal nectary organ. The results showed that the ants that consumed the ‘nectar’ substance stayed with the caterpillar, while the other ants wandered away.
Furthermore, these ‘converted’ ants had the tendency to respond to particular stimuli. For example, when the lycaenid caterpillar raised its tentacles and moved them, the ants reacted to that and tended to act aggressively – by seeking out enemies. On further analysis, it was found that the raising of tentacles is a part of defensive motion by the caterpillar.
And lastly (and most interestingly), the scientists dissected and discovered that the affected ants had decreased levels of dopamine in their brains. They somewhat replicated that effect by feeding a fresh batch of ants a drug called reserpine – that blocks the flow of dopamine. These drug-addled ants were found to have movement lethargy, which was similar in nature to the nectar ‘drunk’ ants. So this might allude to a biological phenomenon where the caterpillar secretion causes the alteration of dopamine levels in ant brains – thus making them more aggressive while being induced by the caterpillar.
The related study was originally published in the journal Current Biology.
Featured Image Credit: Alexander Wild