A MICROSCOPIC worm that has been studied by biologists for decades has been hiding a secret: it can make milk to feed its young 鈥� and it does so in a way that supports the idea that ageing is programmed by evolution, rather than simply being an accident.
The nematode worm Caenorhabditis elegans is used in many biological studies every year but David Gems at University College London and his colleagues are the first to notice that the worms, some of which are egg-laying hermaphrodites, leave smears of brown liquid in their wake after depositing eggs. The liquid came out of the worms鈥� vulvas, the orifice through which they lay eggs, and contains yolk protein.
Experiments showed that the offspring consumed the liquid and grew better as a result. Gems and his colleagues say it serves the same function as mammalian milk. They propose calling it 鈥測olk milk鈥�.
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鈥淲e had no idea that C. elegans, has this primitive form of lactation,鈥� says Marina Ezcurra at the University of Kent in Canterbury, UK.
True milk is unique to mammals. However, other animals, from spiders to pigeons, secrete nutritious liquids for their young.
The C. elegans milk production was triggered by a biochemical pathway called the insulin-like signalling pathway, which is known to promote ageing in many species.
Gems and his colleagues argue that, after laying hundreds of eggs in a few days, C. elegans adults sacrifice themselves by breaking down their bodies to make yolk milk. The implication, they say, is that this form of ageing has been favoured by evolution, because it allows parents to support their young.
鈥淲hat this paper is saying is: 鈥榓geing has a biological purpose鈥�,鈥� says Ezcurra.
Reference: bioRxiv,
