The precious maternal care of the carpenter bee – Le Monde

A carpenter bee ( A carpenter bee (“Ceratina calcarata”) searches for a flower in Canada in August 2021. ISTOCKPHOTO/GETTY IMAGES

Bees are a repository of clichés that seem as deceptive as they are familiar. Let’s draw randomly: They live in large colonies, gathered around a queen, produce honey and have a magnificent yellow and black striped fur. All of this applies to Apis mellifera, our good European bee. But as soon as we move away from this semi-domestic heroine and her twenty-eight subspecies, all our certainties collapse. Of the approximately 20,000 species of wild bees, very few combine even two of the four characteristics mentioned.

The little carpenter bee doesn’t have one. No queen, no stripes and almost no hair. No honey, no beehive. As a solitary animal, it digs its nest in the dead stems of raspberries, rose bushes, clover and sumac and is not afraid of the presence of people. Biologist Sandra Rehan, a lecturer at York University in Toronto, examined Ceratina calcarata for the first time in her garden twenty years ago. “I started with educating young people, monitoring sexual distribution and maternal investments. I ended up decoding its genome and combining my interests in animal behavior and molecular genetics,” she says.

In an article published on September 14 in the journal Communications Biology, the researcher and her team describe in detail for the first time how maternal care from the small insect (8 millimeters, half of a honey bee, one tenth of a large bumblebee) has on its future Offspring, both in terms of the expression of its genes, the production of its microbiota and its general health. Such relationships have already been studied in many species, from birds to mice to humans. But Sandra Rehan and her colleagues followed the processes at all stages of their two-month development: a total of nineteen stages, grouped into four main periods: early larva, advanced larva, pupa and juvenile.

No collective defense mechanism

By comparing litters cared for by their mothers with others left to their fate, researchers were able to see the effects of care at all stages. “We expected this,” said the researcher. But the extent of the consequences in the early larval stage amazed us. » The researchers thus made clear major changes in the expression of certain genes, which they then linked to the explosion of pathogens in the larval microbiota. They found bacteria there, but above all 85% fungi. The most common is Aspergellus, which is also feared by domestic bees. “If the mothers are not there to clean them, the infected larvae are mummified,” says Sandra Rehan. Other pathogens cause abnormalities in eye or brain development.

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