Science

How are the “slave ants” that capture other ants to be their workers

We call them, with all propriety, slave owners.

The slaves are not of the same species, but of another very close from the biological point of view. They enslave their genetic relatives, so to speak. They are the so-called “slave ants”.

Some slave ants capture workers of the species they enslave and bring them to their colony to work for them: they tend to their young, help them defend themselves, find food for them, and keep colonies clean.

The most frequent is that they capture the specimens in very early stages of development, in the form of larvae or pupae.

They take them to their colony and, once they become worker ants, they begin to work for their owners. But in some species they capture adult workers.

Food slaves

The emergence of eusociality in ants —the development of complex societies, with castes of individuals that perform different tasks (work, reproduction, defense) and cooperate to maintain a colony and raise their offspring—, was accompanied by a multiplication of the genes that encode chemoreceptor molecules , both for odor and taste.

The proof of this is the great importance of chemical communication in these species.

For this reason, the fact that slave ant workers are capable of reproducing is of special interest . It could be said that they have regained that trait, which is attributed to the loss of the ability to perceive and respond to the pheromones of the queen ant that inhibit reproductive activity.

In a recent study they have sequenced the genomes of eight species of ants – three parasites, their three parasitized species and two non-parasitized species – to find out if chemoreceptors had been lost in these three parasitic species.

They found that the parasitic species had half as many receptors for taste as the other five species and three-quarters of those for smell.

In other words, in these species it has lost the ability to taste a 50% and Olfactory in 25% . They are capable, therefore, of identifying far fewer substances in these ways than those identified by parasitized ones and the two that are neither parasitic nor parasitized.

The loss of taste receptors is attributed to the fact that these species no longer search for food, because they do it for them – and at their command – the parasitized ones and, therefore, they do not need to receive and decode so much information in this way.

The disappearance of olfactory receptors is attributed, in part at least, to the loss or attenuation of the eusocial condition in these species.

Less social ants

It is perfectly logical that, in the same way that eusociality was accompanied by a multiplication of chemoreceptors, the loss of part of these also entails an attenuation of this very special condition.

Many of the smell genes lost by the parasitic species are common to all three studied. It is, therefore, what biologists call a convergence , since the loss of the genes in question has occurred independently in these species.

Given that such things are highly unlikely to happen by chance, the consequence that is drawn is that it is an advantageous loss, one of which we say is of high adaptive value, probably because producing and maintaining them carries a cost that is not seen. offset by an equivalent gain.

The metaphor is suggestive: in ants, the adoption of slavery entails the attenuation or loss of eusociality and the sensory capacities that make it possible.

Evolution does not follow any time arrow; human history, surely, neither.

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