And that is not done gently; milk production costs them their organs and ultimately their lives.

The only one millimeter large and transparent roundworm Caenorhabditis elegans is a popular model organism. For example, the species is being studied in order to better understand how aging processes work. In a new study, published in NatureHowever, researchers make a surprising discovery. Because not only does the special roundworm appear to make milk, this action is accompanied by a unique self-destructive process.

Confusion

What is so special about Caenorhabditis elegans, is that most have both male and female reproductive organs. This means it can fertilize itself with a limited supply of sperm. When this supply shrinks and eventually runs out completely, reproduction stops. The worms then behave in a way that has puzzled scientists for some time: they generate a large amount of fluid that builds up in their bodies and destroys the internal organs.

Milk

Researchers assumed that this devastating liquid may represent some sort of fatal disease of old age. But a new study now claims otherwise. The deadly liquid also ends up in the unfertilized eggs. And the liquid that is destructive to the mother seems to benefit the unborn larvae. The larvae that have this ‘mother’s milk’ at their disposal, for example, grow a lot faster than larvae that are not given the liquid.

Sacrifice

Basically, as the mother worms age, they secrete a milky fluid through their vulva. This ‘milk’ is then drunk by offspring, which supports their growth. At the same time, this production kills the mother herself. “When we realized that the worms make milk, many pieces of the puzzle suddenly fell into place,” explains researcher Carina Kern. “The worms sacrifice themselves and at the same time provide their young with the necessary nutrients.”

C. elegans secretes the destructive but nutritious ‘worm milk’. Image: Dr Carina Kern

This extremely selfless and sacrificial act helps to unravel some mysteries about the biology of roundworm aging, the researchers say. “The discovery that the roundworms make milk reveals a new way in which Caenorhabditis elegans maximize their evolutionary fitness,” emphasizes Kern. “When they can no longer reproduce because they run out of sperm, they melt their own tissues and transfer the nutrients to their offspring.”

Implications for humans

The study has far-reaching implications. Because it may also shed some light on how we can slow down the aging process in humans. “The amazing thing about aging in Caenorhabditis elegans, is that lifespans can be greatly extended through gene manipulation – it can increase their lifespan tenfold. By understanding how this happens, we may also be able to figure out how to slow down human aging. And that’s really exciting.”

The researchers are continuing their study. Because there is still much to learn about aging processes in organisms. “Ultimately, it is critical to understand the principles governing the aging process of Caenorhabditis elegans determine,” says study leader David Gems. “It is also important to explain the causes of age-related diseases in general. We don’t really understand this in any organism yet. But as for Caenorhabditis elegans we’ll get there. And the discovery of worm milk brings us one step closer.”