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Earthworms
To date over three thousand different earthworm (Phylum Annelida, Order
Oligochaeta, Class Clitellata) species have been described, of which
only about twenty-six described species are present in the UK. Real dversity may be much higher, as molecular methods are revealing many cryptic species. They are the single
largest contributors to total soil invertebrate biomass in
temperate regions and have long been recognised for the benefits they bring to the
environment. In Ancient Egypt, for example, earthworms were considered so indispensable
to the agricultural economy that Cleopatra supposedly declared the earthworm
sacred, and any export of earthworms was subjected to the death penalty.
The importance of earthworm activity in terrestrial ecosystems can be
ascribed to their characteristic burrowing activity, bringing subsoil to the
surface, and the feeding strategy resulting in the mixing of both soil and
organic fractions. Thus, earthworms play a vital role in promoting soil
oxygenation/aeration and in improving soil water relationships. By enhancing
microbial activities earthworms aid in nutrient cycling processes and in soil
structure development.
Because of their environmental benevolence, earthworms are valued not only
by gardeners, agriculturists and horticulturists, but also by agencies
involved in land reclamation following industrial or mining disturbance.
The latter due to the earthworm's intrinsic tolerance towards resident toxic
inorganic and organic residues, and the fact that they help rehabilitate
disused mine sites by creating new topsoil in the presence of organic
amendments. Finally, the close relationship between earthworm quantity
and soil quality has given rise to a wide spectrum of soil quality tests,
which exploit the earthworm as the ecotoxicological sentinal species.
Other earthworms
We have a collection of pictures of identified specimens here.
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