Opening details

The world turns and our physiological clock turns with it. Daylight synchronizes the sequences of molecules responsible for time perception and sleep. A surprising study conducted by the University of California, Davis, revealed the unusual behavior of these molecules in the large black dung beetle (Holotrichia parallela). Scientists say that in all other animals, these “time molecules” can combine with sex hormones to form a kind of partnership, or they can act alone, but always lead. But this insect’s sex hormones appear to take control, creating an internal rhythm that lasts 48 hours instead of the typical 24 hours.

Because this strange internal clock starts and stops twice as long as the circadian cycle, it has been given another name: “circabid” rhythm (circabidian rhythm). The mechanism that creates this cycle is still a mystery.

This species of scarab is an agricultural pest in Asia. They have “lucky chances” to stay up every other night. On these nights, females leave their cozy earthen homes and climb to high ground (for example, a peanut plant) to impress their partners with pheromones. They are of two types: l-isoleucine methyl ester (LIME) and l-linalool.

The team first identified the insect’s sex pheromone receptors and monitored their activity, including measuring the response of the male antennae to the pheromones. The control group was also tested on plant pathogens.

Although insect receptors responded to both LIME and l-linalool individually, the strongest signals appeared when both pheromones were combined. This The binary response of the antennas showed the same two-day pattern in both chemical and electrical signals; whereas the response of insects to plant phytoncides was noncyclical.

These results are puzzling because the biological cycles of animals and insects often overlap over time with external environmental cues such as light or temperature. However, there is no known natural cycle that lasts 48 hours. Therefore, it is not clear with which natural event the scarabs are synchronized.

The circadian rhythm reduces mating opportunities but minimizes predation. However, H. parallela is not under any known hunting pressure.
– writes a team of scientists.

Previous research suggests that although darkness does not disrupt this cycle, light plays a role, as removing the visual lobes disrupts the insects’ synchronization. Thus, there appears to be “a mechanism to double clock cycles in the circuit between clock cells and neurons responsible for behavioral commands.”

At some point, unfavorable conditions must have worked to the insects’ advantage, limiting their appearance to every other day. But exactly what makes their bodies respond to such a unique “program” remains a mystery.