Discovery: A Spider That Makes Milk To Nurse Spiderlings

An unlikely new species has been found to provide milk to its young, researchers revealed on Friday. It has sugar, fat, and about four times as much protein as cow’s milk.

Although lactation and nursing is more commonly associated with mammals, some other animals -- like these jumping spiders -- do the same thing.

A new study, published on Friday in Science, revealed the invertebrate species, Toxeus magnus also produces milk to feed its young.

Researchers at the Chinese Academy of Science made the discovery while following up on an observation about Toxeus magnus -- an ant-like jumping spider.

The spiders are normally solitary, but scientists noticed that groups were hanging out in breeding nests. This included groups of one adult female and several young.

Toxeus magnus -- an ant-like jumping spider.

The researchers also noticed that baby spiders steadily grew bigger, despite never leaving their nests. There was also nothing to suggest their mothers were bringing them food.While recording data on the growing spiders’ body sizes one evening, lead researcher Zhanqi Chen spotted some spiderlings attached to their mother’s body.

“I had many hypotheses, but this one was not included,” Chen told The Scientist. “At that point, I was so excited, I couldn't sleep."

It appeared to him that the spiderlings were latching on to its mother's breast --  just like mammals do.

The group learnt that mothers excreted a milk-like substance from their epigastric furrows, an abdominal opening from which they lay eggs.

The researchers argued that if loose definition of milk is a nutritive substance that's nourishing young, then this is considered milk.

Juvenile spiders sucking milk droplets from their mother. IMAGE: Science

The researchers were able to get a spider, under a microscope, to secrete a few drops of milk “after slight finger pressure on the abdomen,” Chen said.The secretions “really looked like the milk of mammals,”  study co-author Rui-Chang Quan said.

They analysed the liquid and found it has sugar, fat, and about four times as much protein as cow’s milk.

Scientists have previously learned that some non-mammalian creatures also make milk to feed their young.

Cockroaches, for example, nourish their developing embryos with a milky, protein-rich fluid.

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Other non-mammals are known to feed their young substances that their bodies produce. Doves and pigeons, for instance, produce “crop milk” that parents regurgitate for their young.

Here's what else they learnt.

Without access to their mothers’ milk, Toxeus magnus spiderlings die within the first 10 days of life.

During the first three weeks after emerging from their eggs, the hatchlings fed exclusively on their mother’s milk.

Many continued to consume the milk after leaving the nest. According to Chen, this extended period of lactation is more similar to the process typically observed in mammals than in cockroaches (which only use their milk to nourish developing embryos.)

The researchers have several remaining questions they hope to tackle in future experiments.

They want to investigate whether the spiders, like mammals, produce milk in mammary glands.

Out of 50,000 of spiders species, it is likely Toxeus magnus  isn't the only one that produces milk to feed its young.

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Featured image: Chinese Academy of Science