After the war between humans and cockroaches, some cockroaches lost their "love"...

"The orioles are singing on the island in the river. The beautiful lady is the ideal match for the gentleman."

Why is that person so special in the vast sea of ​​people? This unique attraction has not only spawned countless literary and artistic works suitable for being passed down on this day; from a biological perspective, it also plays a vital role in the survival of the population.

In the process of evolution, different animals have developed their own unique ways of displaying sexual attraction, such as peacocks spreading their tails, larks singing, and annoying cicadas and frogs. So what about cockroaches (which will always accompany single people even on Chinese Valentine's Day)? How do they find their ideal lover ?

Even if you never love it, the cockroach will still stick with you｜Cartoon Hangover

——Hey, don’t think cockroach mating is boring. After all, studying how they court may provide some ideas for the fight against cockroaches!

In the vast sea of ​​mantises, I found you

The mating of cockroaches is usually initiated by the female cockroaches. Adult female cockroaches synthesize certain pheromones in their bodies , which are secreted outside the body. They act like tour guides, leading male cockroaches to the female cockroaches.

After that, the male cockroach will touch the female cockroach with its antennae to determine whether the other party is suitable for mating. If the other party is suitable for mating, the male cockroach will turn its back to the female cockroach, spread its wings, and expose its abdomen to secrete pheromones. **These secretions are rich in lipids and sugars, which female cockroaches generally like to eat. **While the female cockroach is concentrating on enjoying the feast, the male cockroach will take the opportunity to stretch out his genitals, hook the other party's genital opening, quickly turn around, and start mating.

Cockroach mating process: After confirming through sex pheromones, the male (B) will spread his wings and present a high-sugar and high-fat betrothal gift to the female (A) | Reference [1]

However, there are thousands of cockroach species in the world, and the situation of each cockroach is different. Take the most common German cockroach (Blattella germanica) in our homes as an example. Their sex pheromones are not spread far and need to be effective through contact. In other words, German cockroaches cannot fall in love online, and they must meet in person to feel the sexual attraction of each other . Their pheromones are therefore called contact sex pheromones.

These sex pheromones are all over the body of female German cockroaches, with particularly high concentrations in their antennae and wings. For male cockroaches, the more sex pheromones a female expresses, the more sexually attractive she is . However, what determines the amount of pheromones?

One gene makes sexual attraction transcend gender

Recently, Li Sheng's team from South China Normal University discovered that, to a large extent, the sexual attractiveness of female cockroaches is controlled by a gene called CYP4PC1 .

CYP4PC1 is a rate-limiting enzyme gene that controls an important step in the production of contact pheromones. CYP4PC1 is only expressed in female cockroaches. As female cockroaches mature, the expression of CYP4PC1 gradually increases; along with it, the concentration of contact pheromones will gradually increase. When the CYP4PC1 gene is artificially suppressed, the contact pheromones in female cockroaches will decrease significantly, and sometimes even become undetectable. The vast majority of female cockroaches that do not express CYP4PC1 have lost their sexual appeal to male cockroaches - and a small number of accidents occurred in the experiment. The researchers are not sure whether these few exceptional cockroaches are because the gene is not completely suppressed, or if they synthesize sex pheromones through alternative pathways.

There are thousands of species of cockroaches in the world, and the ones we are most familiar with are usually the German cockroach and the American cockroach. In fact, many cockroaches don't want to get close to humans at all, and they are so good-looking that they subvert people's perceptions, such as this "domino cockroach" (Therea petiveriana)｜Sripathiharsha / Wikimedia Commons

Although the CYP4PC1 gene also exists in male cockroaches, it is not expressed. This is because the gene DsxM that guides cockroaches to differentiate into males inhibits the expression of the CYP4PC1 gene in males. Because the CYP4PC1 gene is not expressed, male cockroaches do not secrete contact pheromones, which makes German cockroaches have strict bisexual reproduction - they are not like American cockroaches, which may have parthenogenesis, and male cockroaches will not accidentally want to mate with the same sex.

But researchers have discovered that if male cockroaches are made to produce sex pheromones, they can actually "turn gay" towards the same sex.

The researchers tried to inhibit the gene DsxM in male cockroaches, and also tried to inject them with Juvenile Hormone III, a hormone that affects the expression of the CYP4PC1 gene, and its content in female cockroaches is much higher than that in males. It was found that male cockroaches that received these treatments expressed the CYP4PC1 gene and produced contact pheromones. The researchers put these male cockroaches together with untreated male cockroaches, and the wild cockroaches, who knew nothing about it, were guided by the pheromones and opened their wings towards the same sex, releasing courtship signals . And those male cockroaches that were expressed with pheromones, unexpectedly, like female cockroaches, began to lick each other's secretions and even tried to mate with each other.

Swipe left to see the innocent male cockroach being deceived: an untreated male cockroach (B) is trying to show his affection to a male cockroach (A) that has been injected with juvenile hormone 3 | Reference [1]

With this discovery, in the future we may be able to use technologies such as gene editing to prevent female cockroaches from producing sex pheromones, or to make male cockroaches produce sex pheromones , thereby disrupting the cockroaches' courtship and mating, and achieving the goal of controlling the number of German cockroaches.

The war between humans and cockroaches caused the male cockroaches to lose their love

It may take some time for the research on the sex pheromones secreted by female cockroaches to be useful in fighting cockroaches; but the "proposal" process of male cockroaches has already been affected by human cockroach extermination behavior.

As described above, when a male cockroach takes a fancy to a female cockroach, it will spread its wings and offer its secretions to the female cockroach as a betrothal gift . These secretions are high in sugar and fat, not only delicious, but also have high nutritional value. A well-fed female cockroach can provide better development conditions for fertilized eggs. Therefore, this betrothal gift was once favored by female cockroaches.

Before mating, female cockroaches eat secretions from the male's abdomen | NC State

However, not every female cockroach likes this betrothal gift . And this is probably the result of human cockroach extermination.

Most cockroaches love sweets, so people often add fructose and glucose to cockroach baits to lure them. Cockroaches that eat poison will not only die, but often carry the poison back to their nests before they die, so it is difficult for them to leave offspring. Cockroaches that don't like sugar, on the other hand, have a survival advantage - although they don't often enjoy big meals, they also have less chance of accidentally eating poison. They survived the war between humans and cockroaches and passed on the trait of "aversion to sugar".

Unexpectedly, once female cockroaches become averse to sugar, male cockroaches may lose the opportunity to mate . Scientists at North Carolina State University in the United States have discovered that the enzymes in the saliva of these sugar-averse female German cockroaches can quickly break down the polysaccharides in the "bride gift" into monosaccharides. In their mouths, these sugars not only taste not sweet, but even bitter . Originally, male cockroaches would quickly start mating while their partners were licking the bride gift; but now, often before the male cockroaches can react, these sugar-averse female cockroaches have been scared away by the bitter taste, and mating is forced to be interrupted.

When the female cockroach feeds on the secretions, the male cockroach will take the opportunity to hook the other for mating; but if the female cockroach is not satisfied with the food, the male cockroach will miss the opportunity to mate｜NC State

Although the male cockroach has lost his love, humans must be very happy to see this - as the war between humans and cockroaches continues, there will be more and more female cockroaches that hate sugar. Can we look forward to a world with fewer and fewer cockroaches?

Unfortunately, the answer is "not necessarily" - female cockroaches that hate sugar can still mate with male cockroaches that hate sugar , just as two people with the same eating habits can live together (bushi). Scientists have found that male cockroaches that hate sugar secrete different betrothal gifts. Their secretions contain a higher content of maltotriose, a sugar that is not easily broken down into glucose. Therefore, before the female cockroaches that hate sugar have time to taste the bitterness of this betrothal gift, they have been hooked by the male cockroaches, started mating, and then continued to bring more little cockroaches to the world.

This discovery also brings another bad news to humans. When scientists first discovered the existence of sugar-averse cockroaches, they recommended not to add glucose to cockroach baits; but now, even if there is no glucose directly added to the bait, but only other sugars that can be broken down into glucose, it may not be able to deceive these cockroaches...

PS. Cockroaches have strong vitality and are blessed with many children, but few people wish you a love like that of cockroaches...

References

[1] Chen, N., Liu, YJ., Fan, YL. et al. A single gene integrates sex and hormone regulators into sexual attractiveness. Nat Ecol Evol (2022). https://doi.org/10.1038/s41559-022-01808-w

[2] Sugar Aversion Hampers Cockroach Coupling. https://news.ncsu.edu/2022/05/sugar-aversion-hampers-cockroach-coupling/

[3] Cockroach Reproduction Has Taken a Strange Turn. https://www.nytimes.com/2022/05/27/science/cockroach-sugar-sex.html

Author:Hazel

Editor: Mai Mai

This article comes from the Species Calendar, welcome to forward

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