Natures wonders: weird parasitic ants (Introduction)

by David Turell , Sunday, March 05, 2023, 02:38 (628 days ago) @ David Turell

Live quietly in small size-controlled groups:

https://www.sciencedaily.com/releases/2023/03/230303105250.htm

"Called workerless social parasites, these rare species exist only as queens, and they die without workers to tend to them. To survive, parastic ants infiltrate a colony of closely related ants, where, as long as they keep their numbers relatively low, they and their offspring become the leisure class of the colony.

"Now scientists in the Laboratory of Social Evolution and Behavior at The Rockefeller University, together with their collaborators at Harvard University, have a new theory. As they report in Current Biology, they've discovered queen-like mutants -- parasitic ants that spontaneously appeared in colonies of clonal raider ants, which are typically queenless.

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"Among the more than 15,000 identified ant species are hundreds that qualify as social parasites. Born inside a host colony, a parasitic ant will leave the colony, use a sex pheromone to attract a male from another colony to mate with, and once pregnant, will infiltrate the original colony or find another nearby. She'll often use subterfuge to sneak past colony guards. The shampoo ant, for example, will snatch a few ants just outside a nest entrance, lick them to acquire the colony's signature chemical scent, and then lick herself all over to transfer it to her own body. Chemically cloaked, she then can slip inside to live out her life and reproduce both new queens and males who mate outside the colony. The males die, and the queens begin the cycle again.

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"The researchers then ran a series of experiments and genetic analyses. One of the first experiments was to isolate them to see whether the phenotype was heritable. Because clonal raider ants reproduce asexually, they didn't have to worry about interbreeding with other ants.

"The queen-like mutants lay eggs that developed into copies of themselves. "We knew we had something cool," Kronauer says.

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"Despite laying twice as many eggs as their hosts, the ants self-regulate their head count. As long as their numbers stay below about 25 percent of the host population, they do well. More than that and they run into trouble. Queens need help from workers to free their wings as they emerge from the pupae, and if there are too many queens for the workers to look after, they'll die entangled in their pupal skin.

"'They seem to have the ability to regulate their own reproduction so that they don't drive their host colony extinct, which is a very smart thing for a parasite to do," says Trible,

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"Whole-genome sequencing revealed that the parasitic queens have a mutation in chromosome 13, which is structurally similar to chromosomes that regulate colony social structure in other ants. This mutant chromosome seems to contain a "supergene," a set of genes that work together to create a phenotype. In this case, the supergene contains more than 200 individual genes, a disproportionate number of which assist in the metabolism of hormones. These include genes that code for cytochrome p450 enzymes, which are required to synthesize hormones in both ants and humans, and may play a role in the creation of these highly unusual mutants.

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"It appears that with this single mutation, "their form, the higher egg production, the behavior -- it can all shift in a single mutational step," Kronauer says

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"That idea -- that two very different forms of an animal can arise in a single species -- gets at the heart of the mystery of ant castes. Because workerless social parasites arise from a very specific type of mutation affecting ant caste development, studying the queen-like mutants has the potential to reveal insights into the still-unknown molecular mechanisms that allow ant larvae to develop distinct caste morphologies. "It provides a very comprehensive framework in which to study their evolution," says Kronauer."

Comment: Well, it seems ants can think of everything, even inventing their own parasites.