A mother's love isn't necessarily universal across the animal kingdom, with some mothers even resorting to eating children who aren't quite up to scratch.
Ant queens in colonies of black garden ants (Lasius niger) do exactly this, devouring their sick young to recycle their energy into laying new eggs, according to a new paper in the journal Current Biology.
Up to 92 percent of offspring infected with a fungal pathogen were seen to be cannibalized by the queen, compared to only 6 percent of young that were healthy.
"We report that founding queens of the black garden ant (Lasius niger) cannibalise their infected young and that this improves their chances of successful colony foundation," the researchers wrote in the paper.
Black garden ant colonies are founded by a single queen, with her young growing up to form the rest of the colony. These new colonies often fail due to predation, starvation, or pathogenic infection, however. Therefore, if the queen devours any young that are infected with pathogens before the disease can spread, she can ensure the safety of her colony and also fuel the laying of more eggs.
"Ant queens start their colonies alone and essentially starve themselves to raise their first workers. The queens who produce the most workers have the best chances of survival, so being able to eat and recycle infected larvae back into brood production means valuable resources are not wasted," study co-author Flynn Bizzell, a researcher at the University of Oxford's Department of Biology, said in a statement.
Eating ones own children, known as filial cannibalism, is seen in a number of species. This is often triggered by environmental stress, a strategy to reduce competition, or an adaptive behavior to optimize the use of limited resources. Fish species like cichlids, pipefish and gobies often eat part of their brood, especially if resources are limited, or the offspring have low chances of survival, while bird species like storks and coots may eat their weak or unhealthy chicks, and even some mammals, such as lions and rodents, may consume young, especially under stress, overcrowding, or if food is scarce.
"Cannibalising young with low survival probability may enable parents to reinvest valuable resources into future reproduction. However, cannibalizing offspring that harbor pathogens may be potentially harmful to parents, and such risk may therefore select against this behavior," the researchers wrote in the paper.
"Although disease-induced cannibalism of eggs has been reported in fish, the benefits of consuming infected brood to contain infections — as an explanation for the evolution of filial cannibalism — remain largely unexplored."
In the paper, the researchers describe how they presented a queen ant with young that had been infected with a fungal pathogen, which was not yet at the stage where it could be transmitted. They found that the queen ate 92 percent of these infected larvae, but ate only 6 percent of the control larvae, which had not been infected.
"Once the queens find a sick larva in the brood pile they get to work immediately and spend several hours chewing them up until they're all consumed," co-author Chris Pull, also a researcher at Oxford's Department of Biology, said in the statement.
Antimicrobial Venom
All the queens were seen to survive even after eating infected larvae. The researchers suggest this may be due to the queen swallowing an acidic, antimicrobial venom which is produced by a gland on their abdomen, which they observed some of the queens massaging during the process of the cannibalism.
The researchers also found that those who ate their infected young had 55 percent more eggs than queens who did not, suggesting that they recycled the energy and nutrients into making more children.
If the queen was presented with offspring that were infectious, they did not eat them and instead sprayed the larvae with their special venom. Despite this, 80 percent of the queens were then infected and died from the disease.
Interestingly, this behavior was never seen among worker ants, only in queens. The researchers suggest that this may be because queens cannot leave the nest and this is their only way to dispose of the infected young, while worker ants can carry them out of the nest.
"Our results provide compelling evidence that cannibalism solves the problem of disease containment and corpse disposal in the confined space of the founding queens' underground bunker, while also ensuring valuable nutrients are not wasted—and that this improves their chances of successful colony foundation," Pull said.
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References
Bizzell, F., & Pull, C. D. (2024). Ant Queens cannibalise infected brood to contain disease spread and recycle nutrients. Current Biology, 34(18). https://doi.org/10.1016/j.cub.2024.07.062
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