[ID: an illustration of two earthworms arranged in a heart shape on a dark dirt background with stones, twigs, and leaves. Above them, text reads “would you still love me if I was a worm?” End.]
What’s better than one brain? Thirty-two brains! That’s how many brains a leech has. Their bodies are separated into 32 segments, each with its own brain fragment. In addition, each leech has 10 stomachs and nine pairs of testicles, as well as a set of ovaries.
(Image: A pair of mating tiger leeches (Hirudo medicinalis) by David Hemprich-Bennet)
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Most gardeners know that earthworms help keep soils healthy, now scientists have assessed just how important their underground activities are to global food production – and how to protect them.
In research published Tuesday scientists found that earthworms may be to thank for more than six percent of global grain yields every year, because of their crucial role in soil ecosystems.
Worms help to decompose dead plant material, releasing nutrients plants need to grow, and their tunneling helps plant root growth among other benefits.
Evidence suggests they also help plants protect themselves against common soil pathogens by stimulating their defenses.
Farmers and gardeners are often pleased to see earthworms slithering through their soil. But how much do they actually help plants grow? According to the first worldwide estimate of the invertebrates’ contribution to crop yields, earthworms add more than 140 million tons of food each year. For wheat harvests alone, that’s roughly equivalent to one slice in every loaf of bread.
“It is a very important and interesting finding,” says Helen Phillips, an ecologist at Saint Mary’s University who was not involved in the study, published today in Nature Communications. “It really highlights the importance of earthworms, alongside other soil organisms, as providers of ecosystem functions and services.”
Earthworms do many things to make soil more fertile. By feeding on dead plant matter, they release nutrients much faster than soil microbes would by themselves. They also improve the physical structure of soil. As worms digest plant matter, they excrete tiny, stable clumps of particles. Together with the earthworm burrows, these aggregates make soil more porous. This allows rainwater to soak in and enables roots to grow more easily.