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Jumping spiders are already among the most adorable members of the order of the arachnids, but we are ready to give them the prize, officially. A species of jumping spider mimicking ants has just been found breastfeeding her babies with milk. You know what else? Kitties. Doggos. mousies.
But Toxeus magnus is much more diligent than mouse mums. She will continue to breastfeed her babies long after they can feed themselves – and twice as long as rats and mice.
It is a high level of infant care that was thought exclusively for mammals.
"But ScienceAlert!" you say. "Spiders do not have nipples!" (You may also make some rough remarks about the fact that spiders can already to be cute. Some people on our team agree with you on this point.)
Although it's true that spiders do not have nipples, it turns out that T. magnus do not really need them.
The discovery was made by Chen Zhanqi, a behavioral ecologist from the Chinese Academy of Sciences and his team, who noticed some strange behaviors practiced by spiders.
First, although these spiders are not known to form colonies, there are often natural nests containing a number of members, including cultured juveniles. This caught Chen's attention and he brought some of the spiders into his lab for further study.
Once settled in an artificial nest, he noticed a second strange thing: for 20 days, the little spiders had not left the nest and yet, mom did not bring them food.
And then, when the babies emerged, the third strange thing: a miner attached to a mother, like a young mammal under his mother's pacifier – and the mother seemed to be caring for the baby kindly.
Chen and her colleagues started to take a closer look – and discovered that the mother was actually producing some kind of milk for her babies. The substance was rich in nutrients, containing almost four times the protein contained in cow's milk, as well as sugar and fat.
Here's how it goes. The spider mother lays eggs, usually between 2 and 36 years old. When babies hatch, the mother lays tiny droplets of her epigastric furrow, opening onto her abdomen from which she lays her eggs.
Newly hatched babies drink these droplets in the first days of life; but as they gain a little in size and strength, they are able to suck directly from the epigastric furrow of the mother.
This is so that they feed exclusively for about 20 days. This is also usually the length of time that mice and rats suckle before being weaned.
However, although about 20 days later, the spiders can leave the nest and start to find their own food, they continue to complete their search for breast milk for another 20 days, or 40 days in total.
In the laboratory, the survival rate was about 76%. And it seems that prolonged breastfeeding is crucial.
When Chen and his colleagues cut off the mother's milk supply, spiders less than 20 days old died, while those over 20 days old were in good health. Meanwhile, when the mother was completely removed, older spiders tended to leave the nest earlier, did not grow as fast and were less likely to survive to adulthood.
Scientists do not know exactly what the milk is made of, but they suggest that it could be liquefied and unfertilized eggs. Other animals feed their young with unfertilized eggs – frogs, for example, and bees, although usually eggs are laid as usual, and that young people only eat them.
T. magnusMilk could be a similar nutritional source, although it is provided through a different mode of distribution. In fact, the duration of care provided to her baby is rare, even in mammals. It is only seen in a few long-lived social species such as humans and elephants.
"Prolonged maternal care indicates that invertebrates have also evolved [this] capacity, "Quan Rui-Chang of the Chinese Academy of Sciences said Science magazine.
The team's research was published in the journal Science.
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