Things that Yoram knows: Go to the ant

Nir looks in amazement at the rows of industrious ants and asks: Is there slavery in nature? Are the workers enslaved to the queen?

The purpose of every individual in nature is to pass on their genes to future generations. Therefore, the membranous winged social insects (Hymenoptera) was already an enigma for the father of evolution Charles Darwin. The bee or the working ant is notShe lays and yet works hard so that the queen will give birth to more workers and more queens. Darwin had trouble explaining how workers can adapt to the environment and change if a successful worker does not pass on her traits to the next generation? How are several types of workers created that differ from each other in body structure and behavior (for example gathering and guarding workers) if only the queen that does not resemble any of these types reproduces? But the great mystery is the extreme altruism - giving up the ability to reproduce in favor of the swarm or the hive.

To understand the meaning of the unique evolution of social insects, a new theory was required that merges Darwin's principles of selection with genetics. This combination is called "residual selection" and is based on the transfer of genes to the next generation by helping relatives who carry the same genes to reproduce. In fact, in any multicellular creature, most of the cells give up culture and work so that a few cells in the testicle or ovary pass on the shared genes. Every ant in a nest or bee in a hive performs the The same choice that individual cells make in a complex organism: The one who reproduces is not an ant or a bee but a swarm of ants or a beehive that distributes young queens and males that carry with them the DNA common to all individuals. Just as the differentiation into different cell types became possible only when the role of reproduction was transferred to specialized cells only and all competition between the other cells disappeared, so also different types of workers appeared in those insect species in which the reproductive potential disappeared from all but the queen. In some species in which a worker can lay eggs from which males will hatch or take the place of the queen under certain conditions, all workers are indeed similar to each other just as in many primitive multicellular organisms such as sponges in which each cell has preserved the potential for independent reproduction, there is no differentiation into different tissues and organs (because each cell will strive for the maximum chance to realize his ability to reproduce).

The working ant, therefore, is not a slave of the queen just as the muscles in the body are not "slaves" of the testicle or the ovary.

Slavery with ants

Still, there is a phenomenon among ants that biologists call slavery. Several dozen species of ants have developed a lifestyle based on exploiting the labor of captive ants of other species. No less than 35 species of ants are completely dependent on slaves for their survival. In some of them, the workers have lost any ability to gather food, maintain the nest or care for the offspring and have only retained the ability to raid foreign ants' nests and steal pupae. The pupa is the stage of development that the slave trappers aim for because it is passive, the investment in feeding and nurturing is complete and all that remains is to wait for a hard worker to hatch. The pupae are brought to the nest of the enslaving ants and the hatched workers are sealed with the new scent so that their lives will be spent caring for, feeding, protecting their masters and even participating in capturing new slaves from among their own kind. It is possible to find in nature a sequence of degrees of adaptation to the life of a slave owner and in the ants that specialize in this the jaws have taken the shape of a sharp sword capable of stabbing an ant guarding an attacked nest but not digging or collecting food. The evolution of enslaving ants is a one-way street and there is no turning back. It probably begins with the normal behavior of territory battles in which a swarm attacks a nest that has been placed too close and loots the contents. Pupae brought to the nest as spoils of war sometimes hatch before they have had time to be used as food and join the army of workers. In the darkness of the burrows, the identification is done through a characteristic smell and indeed ants enslave only ant species close to them in body scent, nest architecture and diet. If such reinforcement of workers has a distinct advantage and the environment provides many opportunities to import pups, the tendency to aggression will be strengthened and the appetite aroused by the pups will decrease so that the nest will receive a constant supply of workers. This is an example of convergent evolution: the opposing traits required for the survival of the attacking species and the defending species lead to accelerated genetic drift. In the enslaving ant, the functions that are not related to hunting slaves will degenerate and the dependence will become stronger until in some species even the fighting spirit has disappeared: the young queen enters the nest, kills the original queen or sits next to her and receives an "all inclusive" board for the rest of her life.

robbing the nest

When a shortage of working hands is felt, "reconnaissance squads" go into action, locating suitable nests and finding the openings. The patrols call workers and slaves and attack the colony through scare propaganda - activating pheromones that cause panic and chaos under the auspices of which the pups from the nest are robbed. Other species have developed good odor camouflage to the point of being able to enter the robbed nest and remove pupae without causing a backlash. Some highly specialized species even allow pupae of queens and males to reach maturity and bloom in peace, thus enabling the creation of new colonies that can be raided in the future.

The ants used as a victim for slave hunters develop defense mechanisms: they are more aggressive towards strangers and especially refine their scent signature to make it difficult for the enslavers to imitate it. Chemical analysis of the materials in which the ants coat their bodies revealed that pressure from slave hunters encourages the creation of complex cocktails similar to how computer users try to protect themselves from intruders by choosing complicated passwords. For their part, the enslaving ants respond by matching their scents to those of their neighbors, but the refinement of the scent password limits the enslaving ants to a certain type of victim and does not allow for diversification of the sources of sustenance.

And what about the enslaved worker? Until recently, it was assumed that someone who has already been trapped in a foreign nest is trapped in a trap from which there is no way out: after being sealed in her new home, she will not be able to return to the original nest and the instinct that pushes her to do Sisyphean work is too deeply embedded to allow strikes and sanctions. But for about a decade something was renewed in the study of these strange creatures. Biologist Susanne Foitzik reported for the first time a "slave revolt" in ants. It turns out that pupae of the enslaving ant that are handled by slaves suffer from a particularly high mortality. Close monitoring of a large number of nests revealed that no less than 83% of the pupae from which young queens were supposed to hatch died: 30% were torn to pieces by the caretakers and 53% were neglected to death. More than 60% of the bodies of the enslaving female workers had a similar fate. For comparison: among those species of ants that are not enslaved but take care of the females of their own species, the pupal mortality does not exceed 5%. The rebel ants will not gain their freedom and will not return to the original nest and the action is another example of altruism or Choosing relatives. Through aggression towards pupae of the enslaving species, the hostile population is reduced and they avoid raids on their relatives in nearby nests.

Thanks to Dr. Susanne Foitzik for her help.

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