When you have enough to eat, go again. Hey.

Take in nutrition and applaud for love.

It's Valentine's Day again. Most of the humans in the restaurant are in pairs, enjoying the food while expressing their love. A meal is probably enough to pave the way for evening activities.

But if you switch to other animals, it's not so easy to do two tasks at once. Foraging is difficult to courtship, courtship is difficult to find food. In that case, there must be a choice. Scientists have always wondered how animals make decisions between "food" and "sex".

Recently, Professor Jing Wang and his colleagues at the University of California, San Diego (UCSD) finally found the answer in fruit flies and published their research in the journal Nature. They found that when hungry, eating was the first priority, while when full, the male flies quickly entered courtship mode, like pressing a switch.

The important thing is that this "switch" is not in the brain of the fruit fly, but in the digestive tract.

"warm up and think of lust."

In the past, scientists did not understand the physiological connection between eating and courtship.

This time, the team experimented with fruit flies (Drosophila melanogaster). These fruit flies had no sexual experience before the experiment. Some of the males were starved by scientists for 24 hours, while others were fed as usual: they mainly ate yeast, a food rich in protein.

The team asked a hungry male and a female to spend 30 minutes alone in an environment containing yeast (food). Without exception, the male went to dinner first. Some eat for a few minutes, some for more than ten minutes, but after they are full, they all devote themselves to the enthusiastic courtship cause.

When the normally fed male and female flies are alone in a room, the male flies do not need to eat. Some male fruit flies go straight into courtship mode without even eating a bite. Some of the lucky males managed to attract females and reached the mating stage, while the rest of the contestants continued to show their love until the end of their 30-minute solitude.

In other words, during the experiment, no male fruit fly made love to the female when hungry, and no male fruit fly stopped feeding after the courtship mode was activated. It seems that as long as the "switch" is pulled, it will not be pulled back for a period of time.

If you want to ask who triggered the switch, just change the diet of the male fruit fly.

When yeast, a high-protein food, is replaced with sugar, hungry male fruit flies eat for 30 minutes, rarely taking advantage of solitude to show themselves to females. Then, it may not be sugar that orders the male fruit fly to find a partner.

When the yeast in the diet is changed to an amino acid, the hungry male flies enter the courtship process as if they had eaten yeast after eating for a period of time. In other words, eating amino acids or high-protein foods can trigger courtship activities of male fruit flies. Proteins are made up of amino acids, so scientists believe that the substance that pulls the "courtship switch" is amino acids.

So, what is the "courtship switch" that has been pulled?

Raise the priority of courtship

It is a diuretic hormone called Dh31, which is found in many parts of the body of fruit flies. Dh31, which can transmit information between cells, is a kind of signal molecule. The hormone can be produced not only by neurons in the brain of fruit flies, but also by intestinal endocrine cells in the digestive tract.

The team found that when hungry fruit flies ate high-protein foods, Dh31 hormone levels increased. Scientists believe that it is the amino acids in the food that activate the cells in the gut that produce Dh31. In this way, more Dh31 can go to the brain along the circulatory system.

In the brains of fruit flies, there are certain neurons that produce receptors for Dh31, waiting to respond to Dh31. Scientists believe that when Dh31 meets the receptor, it can send a message to the neurons where the receptor is located, allowing them to perform their own tasks, helping fruit flies stop eating and rush to love.

If Dh31 does have this effect, male fruit flies will not courtship even if they are full, as long as they knock out the genes that allow intestinal endocrine cells to produce Dh31. This is how scientists modified the genes of male fruit flies and, as expected, prevented males from pursuing females.

When normal males try to sprinkle their love, those that have been genetically knocked continue to feed. This also proves that the Dh31 hormone is the "courtship switch". Once the switch is broken, no matter how many amino acids you eat, you will not be able to flip the switch again.

So the question is, what exactly are the tasks performed by the nerve cells that pick up Dh31, and why can they raise the priority of courtship activities to the forefront in a few minutes?

Scientists have found that both groups of neurons in the drosophila brain produce Dh31 receptors, both of which bind to Dh31 hormones produced in the digestive tract. But the two groups of neurons perform different tasks, and the soldiers are divided into two groups:

One group inhibited eating with a neuropeptide called allatostatin-C, which is associated with growth inhibition, much like somatostatin in the human body. Another group promoted courtship with a neuropeptide called corazonin, a common neuropeptide in insects that was used by scientists to induce precocious puberty in insect larvae.

These complex brain activities are triggered by a molecule called Dh31 hormone. Professor Wang Jing, who led the study, sighed: "We have witnessed the transformation of fruit flies from feeding to courtship, and it is surprising that a molecule can have such a significant impact on animal behavior decisions."

The study has not yet covered human behavior. But if you feel the time has come after dinner today, please work hard to work miracles.

But do you have a date?