If we had to judge the value of an animal solely by its aesthetic appeal, then the earthworm would not get anywhere near the top of the list. It has no bright colours and has the shape of a pinkish segmented tube. Furthermore, it spends most of its life underground and is hardly ever seen. However, earthworms have an important role in maintaining and enhancing soil fertility and they can be considered a farmer’s best friend.
Earthworms do not have lungs but exchange gases with their surroundings through their skin which must be kept moist at all times. Earthworms are invertebrates: they do not have a skeleton but they manage to maintain their shape by having fluid-filled chambers that function like a hydro-skeleton.
The tiny animal pulls down organic matter such as leaves under the soil surface and converts it to humus. The organic matter is broken down into smaller pieces, partly digested by means of intestinal secretions and ingested together with small pieces of soil.
After digestion, the material is excreted as casts which are high in minerals and can be easily taken up by plants.
The tunnels dug by earthworms bring air into the soil and provide channels through which water can drain.
In good healthy soil there could be up to a quarter of a million earthworms per acre. Numbers can be much lower in soils treated with artificial fertilisers and pesticides.
Earthworms are an important link in many food chains as they are preyed upon by many species of birds including robins, starlings and gulls.
Several species of earthworms are found in the Maltese islands, where they are known as ħniex tal-ħamrija.
This article was published in The Times on 14 February 2013.