Holotrichia parallela
On January 23, 2024, a surprising study from the University of California, Davis, discovered that the black gill beetle (Holotrichia parallela) actually has a unique biological clock, and its internal rhythm only cycles every 48 hours. , instead of the 24 hours we are familiar with!
Just like every time the earth rotates once, our biological clock also rotates. Daylight synchronizes the time molecules in our bodies, sometimes dancing with sex hormones, sometimes waltzing on its own, but always setting the pace. However, these beetles seem to be dancing to a completely different tune.
This strange internal clock is called a “circabidian” rhythm because it is twice as long as a circadian cycle.
While a handful of animals are known to behave in a manner consistent with the two-day rhythm, including humans, mosquitoes, and beetles, the mechanism that generates this cycle remains a mystery. “It’s very rare to observe a 48-hour rhythm in nature,” says Joanna Chiu, an entomologist at the University of California, Davis.
Reduces chances of mating but also reduces risk of arrest
This diagram shows an unusual periodicity in the way a beetle receives sex pheromones. The figure is presented as a weekly calendar showing the relative expression levels of the beetle sex pheromone receptors HparOR14 (marked with a blue pushpin) and HparOR1 (marked with a red pushpin). The activity of these receptors does not occur every day, but shows a pattern of peaking every 48 hours. This shows a unique “two-day cycle” rhythm compared with the traditional 24-hour biological clock. The blue and red curves represent changes in the activity of the two receptors on different days, while the images of the beetles show their behavior during these key days, possibly performing mating-related activities. (Photo/”Contemporary Biology”)
The beetles are a serious agricultural pest in Asia, but they seem to enjoy a date night every other day. During these nights, females emerge from their warm soil homes and climb to high places like peanut plants to attract mates with alluring pheromones called l-isoleucine methyl ester (LIME) and l -L-linalool
Cell biologist Yinliang Wang from the Chinese Academy of Agricultural Sciences and his colleagues found that males responded like clockwork to the perfume.
First, the team identified the beetle’s sex pheromone receptors and monitored their activity through molecular products and electroantennagrams, which measure the response of the beetle’s antennae. For comparison, the researchers also tested the beetles’ response to plant volatiles. Although beetle receivers respond to LIME and l-linlerol individually, the signal is strongest when the two pheromones cooperate.
This dual reaction showed the same overnight (24-hour) pattern in both chemical and electrical signals, while the response to plant volatiles showed no periodicity. These results are puzzling because biological cycles are often synchronized with external environmental cues, such as light or temperature. But there is no known natural cycle that follows 48 hours.
“The two-day rhythm reduces mating opportunities but minimizes predation risk,” the team explains in their paper. “However, there is no known predation pressure on the beetle.”
Previous research has shown that although darkness does not interfere with this cycle, light still plays a role, as removing their visual lobes desynchronizes the beetles. Therefore, there seems to be a mechanism for doubling the clock cycle between “clock cells” and behavioral command “neurons”.
At some point, adverse conditions must have favored the beetles that restricted themselves to emerging only once every two days. But exactly what makes their bodies respond to this unique rhythm remains a fascinating mystery.
The research has been published in Current Biology.
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Source of the first picture: Tomorrow Science
Image Source:Current Biology cc By4.0
Reference papers:
1.Circabidian rhythm of sex pheromone reception in a scarab beetle. Current Biology
Further reading:
1. “To touch the grasshopper and wash the pants at the same time?” Reindeer rumination can replace sleep: saving time to survive in summer
