Perhaps, as early as the monster movies of the fifties, you may have seen mutant ants, but when science fiction became a reality, the task of cultivating mutant ants was challenging. For decades, biologists have successfully altered the genetic traits of mice, rice, fruit flies and many other organisms, but ants, because of their complex life cycle, research on genetic variation has been stalled.
Recently, two independent research groups published two research papers on knocking out ant genes in the journal Cell, along with another study using brain hormones to change ant habits.
Claude Desplan, a biologist at New York University and one of the authors of the paper, revealed that ants are the first social insects to successfully achieve genetic mutation.
Despite genetic similarities, ant populations have very different social divisions of labor within them. Females may become reproductive queens, infertile worker ants, or ferocious soldier ants. Male ants have wings, have a short lifespan, appear only at specific times, and exist exclusively for mating. Therefore, in order to ensure that the mutated genes are passed on from generation to generation, it is necessary to use queens to reproduce.
Daniel Kronauer, a biologist at Rockefeller University, believes that ants have many biological problems worth studying, which fruit flies and mice cannot do. If a thousand fruit flies are put in a dirty bucket, they will only fight or mate, while the ants will nest, breed, and forage in a step-by-step manner.
Epigenetics mainly studies the effects of the explicit and recessive properties of genes on individual traits of insects. The magic of ants is that in the case of the same genes, the same ant may become a queen, worker ant, or soldier ant.
Desplan's team chose the Harpegnathos saltator as the subject, which is special in that all ants have the potential ability to reproduce. Before laying eggs, worker ants must first become pseudo queens. If the colony loses the queen, the worker ant will undergo a ritualized tentacle duel, and the winner will become the pseudo queen.
Kronauer and Rockefeller Graduate Student Waring Trible studied the Ooceraea biroi. Unlike most common ants, the breeding of the Coarse-horned Ant belongs to the virgin birth of asexual reproduction, and the offspring eventually become clones of the female ants. This reproductive phenomenon is also common in the reproduction of snakes, lizards and sharks. The two different studies have the same purpose: to breed mother ants that can carry mutated genes.
The scientists used CRISPR-Cas9 to engineer ant genes to weaken the expression of pheromones, a key component in olfactory receptors.
Although there are hundreds of olfactory genes in ants, knocking out a specific gene orco (odorant receptor co-receptor) will directly cause the ant's olfactory system to lose its function.
"Knocking out every olfactory gene is impossible," Kronauer says, but orco has a decisive role. After knocking out the gene, the ant loses 90% of its sense of smell.
The gene-edited Indian jumping ant has changed significantly, leaving the population and no longer foraging. If a mutant Indian jumping ant is isolated, although other ants can still participate in reproduction, the pseudo-queen spawns fewer eggs and has less reproductive ability. If these mutants were placed in a colony of queens, they would not engage in tentacle duels. Instead, they just swing their tentacles when they're alone, as if practicing boxing.
The elliptically imperceptible pheromone-like Coarse-horned Ant also behaved abnormally. Normally, they avoid the smell of markers, but gene-edited ants crawl on marker lines.
Like the Indian jumping ant, the mutant of the Roughhorn ant is no longer social. They no longer blend into the population, go around, and don't crawl with the pheromones produced by other ants, as they used to.
There are also some strange phenomena that arise. A mutant female ant steals an egg and uses its tentacles to begin hatching. Suddenly, it began to secrete an excess of warning pheromones, causing other non-mutant ants to become restless.
Today, scientists have successfully implemented the use of gene editing to change the social behavior of ants. Next, Kronauer plans to study how the division of labor is within ant populations.
For example, if two people live in the same apartment, when dirty dishes pile up, roommates with "cleanliness habits" will wash dishes more diligently and thus become "dishwashing experts". Previous research methods will be to change the external environment (remove the dishwasher) and observe what phenomena will occur. Through genetic regulation, Kronauer plans to directly regulate the ants' internal thresholds.
In addition to sensory perception, Desplan is also interested in the lifespan of ants. Worker ants live about seven months, and after becoming pseudo-ants, they can live for four years. It's like one person living to be 85 years old and another person living to be 550 years old.
Worker ants who become pseudo-queens return to their identity and die within a few months once they come into contact with new queen pheromones. This means that there must be a reversible genetic switch to control the lifespan of the ants.
Other biologists, including bee research experts, are keeping a close eye on the mutant ant model and considering a similar protocol for studying other species.
Desplan believes that the success of the mutant ant model has laid a solid foundation for gene editing in other animals. If the traditional approach to biology is to study model organisms like fruit flies and mice, genetic engineering could allow biologists to study more suitable animals.
Some entomologists become experts in the study of ants because they have a "deep love" for them. For his part, Desplan has "fought alongside" many insects, including fruit flies, wasps and butterflies. And now there is one more item on the list - mutant ants.
"We became ant experts because of the needs of the job, not because of nature." If these mutant ant models meet Desplan and Kronauer's expectations, the number of experts in this area of research will increase further in the future.