You probably wouldn’t choose microscopic roundworms as the nurturing kind, but here’s a fun fact for your day — these commonly studied nematodes spray a kind of egg milk out of their vulva to feed their young.
Caenorhabditis elegans larvae that feed on this egg yolk milk grow faster than those that do not, a new study reveals. So just like with mammals that supply milk to their babies, this gives the next generation of worms a useful boost in fitness with which they can meet their new world.
And it costs a disastrous price for the mother.
Mother C. elegans are hermaphrodites, meaning they have both male and female genitals. Males are also found, but are extremely rare in the wild.
So even though they may fertilize their eggs sexually, mother worms most often fertilize themselves. But their supply of self-semen is limited; when they stop giving birth to young, their bodies commit to producing egg yolk milk.
These microscopic, transparent vertebrates lay more than their own body weight in eggs, which they secrete as just egg yolk or still completely intact oocytes. But they get them by melting down and reusing their own organs, including intestines and muscles.
“The worms destroy themselves in the process of transferring nutrients to their offspring,” explains University College London bioscientist Carina Kern.
“And all the unfertilized eggs are full of milk, so they act as milk bottles to help with milk transport to feed baby worms.”
This may seem surprising, however C. elegans is far from the only invertebrate species that delivers highly nutritious secretions to their young. Jumping spiders do that too, and so do cockroaches. In addition, many other animals also sacrifice themselves for their young, including squid and salmon.
In experiments, Kern and colleagues demonstrated that larvae that fed egg yolk grew faster than those that did not, even after returning to their usual food. E coli.
The biochemical cycle that triggers the transformation of organs into eggs inside their mother, the insulin-like signaling pathway, is known to shorten their lifespan. In fact, this road is one of the many reasons why C. elegans has been so well studied because on an evolutionary level it is well preserved across many animals, including humans.
Scientists have been using the mini earthworms to study aging, memory, and other foreign objects since the 1960s. They are so valued for research that they were the first multicellular animal to have their genome sequenced.
Kern and colleagues suspect that the timing of the worm’s egg yolk milk production may also coincide with when their colony begins to empty its food. In the wild, C. elegans are thought to reproduce rapidly as they conquer new territories and slur bacterial tastes in their dirt homes. They form large colonies that experience huge booms and busts in populations.
If the mother gives her offspring a head start as the food supply declines, they are more likely to survive – an evolutionary process called family selection.
Unfortunately, this impressive self-sacrifice also means exciting studies about C. elegans genes that massively prolong the life of the roundworm may only work because they prevent this reproductive suicide.
But that does not mean we can still not learn much about aging them. Researchers believe that many of these worming mechanisms are still similar to those seen in other animals, so they have insight into many diseases we all face.
This study was published in Nature communication and an accompanying notification in Boundaries in cell and developmental biology.