How many times can a worm be split in half and still grow back?

Thursday 29th July 2010
Submitted by nikkiwithers
MARTIN HARRISON, BY EMAIL

To a biologist, ‘worm’ refers to many, quite different organisms. The ability to re-grow body parts differs enormously between them, although tails are generally easier to re-grow. If you mean earthworms, their tails usually die when severed, while for many other species the head portion (down to the ‘saddle’) can re-grow a tail – although often a stunted one. Some species can also regenerate the very front of the head.
My guess is certain earthworms could fully regenerate from one specific quarter of their body, although it’s not really known and cruel to try and find out – most would end up dead or stunted.
Some non-British earthworms can even repeatedly re-grow lost tails, although other segmented worms beat that: many reproduce asexually by severing themselves repeatedly, and parchment worms can entirely regenerate from just their 13th body segment.
However, the distantly related planarian flatworms have more extraordinary regenerative powers. Some Dugesia species can fully re-grow from random body fragments of about 10,000 cells: approximately 1/20th of the adult body size. 

GOT A QUESTION?

Scratching your head over a burning scientific conundrum? submit your question and we'll get our esteemed panel of experts to answer it for you.

 

Do whales sleep?
previous qanda Article
What is the largest animal ever eaten by a Venus flytrap?
next qanda Article
Q&A Tabs

Ordinary glass absorbs 97 per cent of the UVB rays that cause sunburn and some skin cancers, and 37 per cent of the less harmful UVA radiation. This translates to a protection of about SPF30, so...

It’s called trypophobia and it’s not a fear of open man-holes or caves. Rather, it is the revulsion some experience when they look at asymmetric clusters of small holes, or dark spots...

Temperature affects the way your brain works, and fever can produce waking hallucinations and vivid imagery as well as nightmares. Some people find that too much spicy food leads to nightmares,...

It depends on the temperature of the water. In cold water, the bacterial action that causes a body to bloat with gas may be so slowed that the body stays on the seabed. The skin will absorb water...

Not for long. The gruesome idea of nails and hair continuing to grow on a rotting corpse is fascinating. But it’s a myth – at least if you’re thinking of luscious locks and long...

All female mammals have a clitoris, the sole purpose of which is to react to sexual stimulation, and presumably this stimulation has evolved to be pleasurable for most species. But establishing...

To create a sound, we have to set matter - whether it's a gas like air, a liquid or even a solid material - in regular motion, creating a wave of specific frequencies, which we hear as a sound of...

Mirrors don’t reverse left and right either – that’s just our interpretation of what happens. Your reflection in the mirror is actually reversed front to back – if you have...

Discovered by an American student named Gary Flandro in the mid-1960s, the slingshot manoeuvre usually involves spacecraft briefly 'coat-tailing' a planet orbiting the Sun, extracting some of the...

The ice disappears because the wind blows away water molecules that have evaporated or 'sublimed' from the ice, so the ice slowly shrinks in size. The molecules that escape are those with the...