LOL! This ant is so good at acting when it is slightly injured, just to let its teammates carry it home...

If someone is injured or sick, they have to go to the hospital and see a doctor. This is common in human society. But you may not expect that ants, who have existed on Earth for 150 million years, have even developed a "cooperative medical system"!

These little guys can provide a variety of "medical services" for their injured companions, from wound disinfection to amputation surgery, from infection prevention and control to precision nursing. What is going on?

Ants' "battlefield rescue"

The Matabele ant ( Megaponera analis ) of the African savannah can grow up to 25mm in length. It is ferocious by nature and mainly feeds on termites.

Large worker ants in Matabele ants. Image from wiki

However, when attacking termite nests, they are often counterattacked by termites. Some ants will lose their legs in the melee, or even be bitten by termites. But their fate will not end here - because reliable companions will quickly come to the rescue.

A study published in Science Advances in 2017 showed that lightly injured worker ants, such as those who lost two legs, would secrete dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS), activating rescue behavior. After receiving the "help" signal, their companions would carry them back to the nest. After returning to the nest, the injured would be "treated" within 24 hours, and after recovery, their movement speed would be close to that of normal worker ants.

Experiments show that the mortality rate of slightly injured worker ants left alone can reach 32%, while the mortality rate of worker ants rescued and brought back to the nest is close to 0%. However, worker ants with more serious injuries (such as those who have lost five legs) will be abandoned. Through mathematical model calculations, the rescue behavior of Matabele ants can increase the population size by 28.7%.

Interestingly, sometimes ants that are only slightly injured will take the initiative to "pretend to be sick." When their companions approach them, they will slow down their movements or even pretend to fall down, appearing to be more seriously injured; but once their companions leave, they will quickly recover their ability to move. This "show of weakness" behavior can increase the possibility of being rescued.

Ants have their own pharmaceutical factories

In a study published in Nature Communications in 2023, researchers found that Matabele ants also have a complex " drug system " that can be used in wound care. The secretions of the metapleural gland of this ant contain 112 compounds and 41 proteins, half of which have antibacterial and wound healing properties, such as the following:

Short-chain fatty acids (such as formic acid and acetic acid): regulate wound pH and inhibit bacteria

Alkaloids: natural antibiotics that destroy pathogen cell membranes

Lysozyme: breaks down bacterial cell walls

Melanin precursor: promotes wound coagulation

In addition, these "ant doctors" can analyze the epidermal hydrocarbon (CHC) content of infected individuals, accurately diagnose the infection status of injured individuals, and then mobilize the proteins and antibacterial compounds secreted by the metathoracic glands for appropriate treatment, which can be said to be "the right medicine for the right disease."

Experiments have shown that when a companion is infected with Pseudomonas aeruginosa, specific changes will occur in the chemical signals on their body surface, triggering companions to strengthen care. This complete medical chain from prevention to treatment has increased the survival rate of infected individuals to 90%, which can be said to be very effective.

Micro-CT scan showing the location of the posterior thoracic glands. Source: Reference [3]

If it can't be cured, you can cut it

On the other side of the ocean, although the Florida camptonotus floridanus does not have a metathoracic gland, scientists have discovered their even more amazing medical behavior - these ants can perform amputation "surgery ."

Studies have shown that when a worker ant's femur is injured, other worker ants will repeatedly bite the femur until the injured leg is amputated, with a postoperative survival rate of about 90% . In addition, Florida bow-backed ants will choose treatment methods based on the type of injury.

Trochanter, femur, tibia location source: wiki

Experimental data showed that after worker ants were injured in the femur, 76% of cases were amputated by their companions, while ants with injured tibia were treated with "conservative treatment" - continuing to lick the wound . Interestingly, when the experimenters tried to imitate ants to perform amputation surgery on cases of tibia injuries, they found that tibia amputation surgery actually significantly reduced the survival rate of injured ants, from 75% to 15%.

Schematic diagram of the hind leg of the Florida Camponotus florida: A. 3D reconstruction of the hind leg, the white dashed line represents the injury site, the red dashed line represents the ant and the human surgery site; B. Section of the trochanter surgery site, C. Section of the femur injury; D. Section of the tibia injury. Source: Reference [4]

After CT scanning, the researchers found that the area of ​​the hemolymph channel in the ant's tibia is twice that of the femur, which means that tibia trauma will cause a faster systemic infection. In order to cope with this possible rapid infection, immediate amputation is a safer option.

However, since the amputation operation by the "surgeon" takes about 40 minutes and cannot effectively prevent the spread of bacteria, they will choose to spend longer time through "debridement surgery" to reduce the possibility of infection. This study shows that ants can choose the best treatment based on the location of the wound!

In fact, in addition to the "medical operations" of ants mentioned above, some insects (including ants) can even do " disease prevention ". For example, some species of ants and bees can collect antimicrobial agents (such as gums, etc.) from the environment and bring them back to the nest. Some ants can also secrete some formic acid-rich disinfectants to disinfect new nests. Termites will remove dead members from the nest, and bees will raise the temperature of the hive by flapping their wings, which can kill temperature-sensitive pathogens (Sylvia 2019; Contemporary Biology).

Ants do not have their own hospitals or medical schools, but after a long period of evolution, they still have such complex "medical behavior". Although it cannot be simply compared with human medicine and wisdom, all of this can still bring us surprise and curiosity about nature and evolution.

References

[1]Frank, ET, Schmitt, T., Hovestadt, T., Mitesser, O., Stiegler, J., Linsenmair, KE, 2017. Saving the injured: Rescue behavior in the termite-hunting ant Megaponera analis. Sci. Adv. 3, e1602187.

[2]Frank, ET, Wehrhahn, M., Linsenmair, KE, 2018. Wound treatment and selective help in a termite-hunting ant. Proc. R. Soc. B. 285, 20172457.

[3]Frank, Erik.T., Kesner, L., Liberti, J., Helleu, Q., LeBoeuf, AC, Dascalu, A., Sponsler, DB, Azuma, F., Economo, EP, Waridel, P., Engel, P., Schmitt, T., Keller, L., 2023. Targeted treatment of injured nestmates with antimicrobial compounds in an ant society. Nat Commun 14, 8446.

[4]Frank, Erik.T., Buffat, D., Liberti, J., Aibekova, L., Economo, EP, Keller, L., 2024. Wound-dependent leg amputations to combat infections in an ant society. Current Biology 34, 3273-3278.e3.

[5]Sylvia Cremer, 2019.Social immunity in insects,Current Biology,Volume 29, Issue 11, ,Pages R458-R463.

Planning and production

Author: Denovo team popular science writer

Review丨Huang Chengming, Professor of Hainan University

Planning丨Ding Zong

Editor: Ding Zong

Proofread by Xu Lailinlin

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