AsianScientist (Feb. 21, 2018) – In a study published in the journal Royal Society Open Science, a research group in Japan has discovered that ant clones have varying thresholds for sweet treats, suggesting that factors other than genes play a role in ant behavior.
Colonies of some ant species such as Strumigenys membranifera reproduce by asexually cloning themselves. These ants have the same genes, with the exception of random mutations. Thus, their reactions to sweetened water should be the same if determined at birth.
In this study, however, researchers at Hokkaido University observed that clonal ants had diverse responses to sweetened water. Dr. Eisuke Hasegawa of Hokkaido University and colleagues tested how strong a sucrose solution had to be so that individual ants would drink it within one minute of detection. This indicated the ants’ response threshold.
The researchers found significant variation between 82 workers from two groups of cloned ants. Some preferred a one percent sugar solution—the equivalent of diet soda—while others would not drink until the concentration of the sugar solution approached 10 percent, more like a regular soda.
The team thus suggested three hypotheses: the threshold could be set during the larval stage and remain unchanged; it could increase or decrease in one direction with age; or it could be randomly determined by external factors during adulthood.
They observed that ants which had recently transformed from larvae to adults had a much stronger preference for more concentrated sucrose solutions than the older adults. Furthermore, 44 percent of adult ants shifted their threshold between the first test and a second test one month later. Some eventually preferred sweeter solutions, others eventually toned down their sweet cravings, while yet other individuals maintained their original preference.
These results indicated that the sweetness threshold is not set at the larval stage, it can change in adults over time, and it is not determined by aging alone, thereby strongly suggesting that epigenetic modifications—chemical modifications to DNA that affect gene functions—are involved. The researchers plan to conduct further studies to confirm whether epigenetic changes are occurring in the clonal ants’ genomes.
The purpose for all this variety remains unclear, but ecologists have found that response threshold variation supports long-term colony survival of social insects like bees and ants. For example, Hasegawa’s team previously found that colonies with both active and lazy ants had reduced short-term productivity, but persisted longer than colonies with only active workers.
“Our study shows even clonal colonies have behavioral variations that could affect the survival of the colony. This is of significance in the sense that temporal epigenetic regulation could lead to permanent changes to the genome, and therefore evolution,” said Hasegawa.
The article can be found at: Hasegawa et al. (2018) Adaptive Phenotypic Variation Among Clonal Ant Workers.
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Source: Hokkaido University; Photo: Eisuke Hasegawa.
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