Humans are not the only ones trying to avert sugar-rich foods as cockroaches have also reportedly evolved to a glucose-free diet. According to ZME Science, the new study claims that German cockroaches (Blattella germanica), one of the most common pests in the world, avoid sugar because they have learned to avoid pesticides that are masked with sweet glucose.
However, researchers from North Carolina State University also revealed that sugar aversion behavioral mechanism has affected the cockroach mating rituals and has resulted in rejected males.
Sugar-Loving Male Cockroaches Rejected By Females
The cockroach mating process usually involves the males giving females a pre-mating gift of body secretions with sugar and fats to attract a potential mate and hold females long enough for successful copulation, Science Daily reported. Co-corresponding author Coby Schal compares it to giving flowers and chocolates to humans during Valentine's Day.
Males would raise their wings and release these chemicals via the target gland on their backs which attracted females will feed. While the female is busy feeding on those chemicals, males would grab her using their elongated penis and move into a mating position. However, this is where sugar-averse females start to reject the sugar-loving male.
The courtship only lasts for several seconds, but the mating process is a 90-minute session in which the male would use a second penis to transfer sperm into the female. If the male is rejected, it results in unsuccessful mating.
Sugar-averse females get an unpleasant surprise when their saliva and male secretions mix because the saliva degrades the sweet treat into glucose that becomes bitter for them, ending their courtship and the female running away without mating.
In 2013, a study by co-corresponding author Ayako Wada-Katsumata published a paper that showed the neural mechanism of German cockroaches that might have become more pronounced in the presence of sugar. Then in 2021, Wada-Katsumata and Schal showed in a paper that cockroach saliva converts complex sugars into glucose. But the female's saliva breaks down this glucose and senses a bitter taste and stops feeding and mating with the male cockroach.
Male Cockroaches' Solution to Sugar-Averse Females
Researchers performed various experiments to see how glucose aversion affected the cockroach mating process, EurekAlert! reported. They found that glucose-averse male cockroaches produce higher levels of maltotriose in their secretions that are not easily converted to glucose, so females feed longer on them and give males extra time to mate.
The researchers also tried substituting fructose for glucose and maltose secretions. They found that females liked fructose more and fed on it longer, which resulted in a successful mating session.
It shows that the quality of secretion affects female behavior and the mating success of cockroaches, suggesting that it is a tradeoff between sexual selection and natural selection. That means that sugar-loving traits evolved under natural selection, but sexual selection forced male cockroaches to change the composition of their secretions and behaviors.
Researchers predict that future generations would develop this genetic variation to avoid sweet poisonous bait that saw their lives and reproductive capabilities cut short. In turn, it forces humans to rethink current pest management control techniques.
They discuss their findings in full in the study titled "Rapid Evolution of an Adaptive Taste Polymorphism Disrupts Courtship Behavior," published in Communications Biology.
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