When a black garden ant queen detects that her larvae are sick, she will eat them before the illness spreads to other parts of the nest. A recent study published on bioRxiv suggests that queen ants aren't in the running for "Mother of the Year," but this strategy might be an effective way to protect their kingdom. This discovery sheds new light on the evolution of cannibalistic behavior among relatives.
A colony of black garden ants in their nest. Image source: Nik Bruining/Shutterstock
Ants and other social insects can prevent the spread of diseases by having worker ants undergo self-isolation when sick or by driving away infected comrades. This "social immunity" phenomenon is well-known, as described by Flynn Bizzell and Christopher Pull from the University of Oxford in their paper. However, since queens found colonies alone, how do they ward off diseases during the process of nest establishment and expansion?
To find answers, Bizzell and Pull collected newly mated black garden ant queens and brought them into the laboratory. Once the queens started laying eggs and the colony began to emerge, researchers removed some larvae from the queens and exposed them to lethal spores of the green fungus, which infects wild ant nests. After allowing these larvae enough time to develop lethal but non-transmissible infections, the research team returned all larvae to their mothers.
The queens consumed 92% of infected larvae but only 6% of uninfected ones, indicating their ability to detect and intervene with infections. Failure to control the infection could have catastrophic consequences. When the research team exposed the colony to highly infectious corpses of larvae covered in sporulating fungi, all ants perished. Even spraying acidic antifungal venom on the corpses only resulted in 20% survival among the queens.
Despite the risks involved, consuming infected larvae seems to be a beneficial strategy for queens. Researchers suggest that queens might ingest their own venom, making their intestines resistant to fungal spores. This conclusion is based on previous observations of worker ants ingesting venom and queens grooming venom gland openings.
Sebastian Stockmaier from the University of Tennessee, Knoxville, remarked, "If a queen becomes infected and dies, the colony collapses because she is the only individual capable of reproduction. Therefore, it makes sense for evolutionary strategies to emphasize the survival of queens in response to diseases."
Consuming infected larvae also has other benefits. Researchers found that queens who consumed infected larvae laid 55% more eggs than those who didn't, indicating that they recycled these energy resources. Researchers believe that this advantage, combined with the elimination of disease risk, suggests that some species may have evolved a form of cannibalism between relatives.
The study results indicate that behaviors necessary for caring for larvae and disease prevention overlap in incipient ant colonies. Thus, Bizzell and Pull suggest that ant disease prevention behaviors may have evolved from the widespread parental care observed in many insects.
Related paper information: https://doi.org/10.1101/2024.03.13.584778
