Mothers provide milk-like fluid to their offspring

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Post-reproduction Caenorhabditis elegans Nematode mothers exhibit a primitive form of lactation, releasing yellow milk through their vulva that can improve the growth and reproduction of their larvae, according to new research from scientists at University College London.

Yellow in the intestinal lumen of Caenorhabditis elegans larva after being left on a plate without food except the vented yolk for 4 h. Above: Nomarski microscopy image. Bottom left: Larva imaged immediately after plaque removal using confocal reflectance microscopy (RCM) to highlight the refractive material of the terminal web that surrounds the intestinal lumen (red) and image d superimposed airyscan (green) for yellow marked GFP. Bottom right: the same larva photographed 100 min later, showing the yolk which is no longer in the lumen, either due to defecation or digestion; this disappearance confirms that the green fluorescence indicated in the central panel corresponds to the yellow within the intestinal lumen. Ladder bar – 20 m. Image credit: Kern et al., doi: 10.1038 / s41467-021-25821-y.

“We have now explained a unique self-destructive process observed in nematode worms,” ​​said Professor David Gems, a researcher at the Institute of Healthy Aging at University College London.

“It is both a form of primitive lactation, which only a few other invertebrates have demonstrated, and a form of reproductive suicide, as the mothers of the worms sacrifice themselves to support the next generation.”

More Caenorhabditis elegans nematodes have both male and female reproductive organs, so mothers reproduce by fertilizing themselves with limited stocks of sperm. When these run out, a few days after sexual maturity, reproduction ceases.

The nematodes then behave in a way that has puzzled scientists for some time: they generate large amounts of yolk-rich fluid that collects in large puddles inside their bodies, destructively consuming them. internal organs during the process. They also lay more than their own body weight in unfertilized eggs.

Scientists previously believed that these changes were futile and represented a form of old age disease.

“Once we realized that post-reproductive worms were producing milk, a lot of things suddenly made sense,” said Dr Carina Kern, also from the Institute of Healthy Aging at University College London.

“Worms destroy themselves by transferring nutrients to their offspring. “

“And all of these unfertilized eggs are full of milk, so they act like milk bottles to help transport milk to feed the babies to worms.”

Previously, researchers have shown that the production of yolk at the end of its life is a self-destructive process.

In long-lived mutant worms, which are specially bred and intensively studied to try to understand aging, self-destructive yolk production at the end of life and egg laying (unfertilized eggs) are disabled.

New study provides potential explanation for how genes control Caenorhabditis elegans lifespan: by regulating this self-destructive process.

The authors found that the milk-like liquid appears to be beneficial for the larvae, as they found evidence that the larvae would indeed ingest the worm milk, and that the larvae that had access to a source of milk – that they also called “yellow milk” – grew faster.

“The existence of worm milk reveals a new way of Caenorhabditis elegans Maximize their evolutionary capacity: When they can no longer reproduce because they have run out of sperm, they melt their own tissues in order to transfer resources to their offspring, ”said Dr Kern.

The new findings could also have far-reaching implications in terms of the prospects of being able to slow down the process of human aging.

Such self-destructive and life-shortening reproductive effort is typical of organisms such as Pacific salmon that exhibit suicidal reproduction. The new study suggests Caenorhabditis elegans lifespan can also be limited by suicidal reproduction.

“What is amazing with aging in Caenorhabditis elegans is that lifespan can be dramatically increased by genetic manipulation – up to 10 times, ”Prof Gems said.

“This suggests that by understanding how this happens, one could find the key to slowing down human aging, which is really exciting.”

“But if Caenorhabditis elegans life extension is simply due to the suppression of suicidal reproduction like in salmon, so the possibility of applying our knowledge of aging worms to dramatically extend human life suddenly seems a long way off.

The to study was published in the journal Nature Communication.

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CC Kern et al. 2021. C. elegans gives offspring yellow in a primitive lactating form. Nat Common 12, 5801; doi: 10.1038 / s41467-021-25821-y


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