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Lumbricus terrestris hatchling and spent cocoon


Frequently aksed Questions «

If you want to know more about earthworms take a look at these FAQs
or
if you have a question regarding earthworms please email Dr Chris Lowe at cnlowe@uclan.ac.uk

QUESTIONS

 

ANSWERS

Why are earthworms important?

Charles Darwin was the first scientist to recognise the importance of earthworms which he described as “natures plough”. Today the beneficial effect of earthworms on the physical and chemical nature of soils is well established. Through their burrowing activities earthworms increase rainfall infiltration rates, improve soil aeration and allow greater root development. Casting increases the proportion of water stable aggregates, improving soil water holding capacity and developing more friable topsoil. The incorporation of organic matter through casting and surface removal of litter, and its mixing with the mineral soil also leads to enhanced nutrient availability.

The role of earthworms in soil fertility has led to their introduction by man, with varying degrees of success, into areas of land often lacking earthworms in attempts to increase plant production in agricultural land, and enhance soil amelioration in degraded land.

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If I cut an earthworm in half do both bits survive?

Usually if you cut an adult earthworm in half the head end (the bit with the saddle) may survive but the tail end eventually dies when food resources are exhausted (It may continue to wiggle for some time).

Why do earthworms come to the surface when it rains – are they drowning?

Earthworms respire through their skin and as a result need to be in contact with moist substrate. It has been suggested that earthworms utilise the moist conditions during periods of rain to migrate over the soil surface.

What do earthworms eat?

In terrestrial ecosystems the main source of food (organic matter) is litter from above ground plants. However, dead roots and rhizodeposition (material transfer form roots to soil) are also important food resources and earthworms have been observed ingesting living roots. Within farming systems animal dung may also form an important, but localised, food source for several, usually litter dwelling, species and result in their aggregation under dung pats.

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Can earthworms see?

Earthworms do not possess eyes, but they do have sensory cells with a lens like structure located in regions of the skin that respond to light stimuli.

How do earthworms move?

Earthworms burrow thorough the soil by co-ordinating contractions of the longitudinal and circular muscle bands that lie in the body wall. These contractions are made possible by the segments being kept turgid by the coelomic fluid. This co-ordination allows the earthworm to pass contraction from segment to segment in a wave effect thrusting the earthworm forward.

How big can an earthworm grow?

Earthworm size varies with species type; however the largest earthworm species is the Gippsland earthworm from Australia that has an average length of 80 cm and a diameter of 2 cm.

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How do earthworms reproduce?

Even though hermaphrodites (male and female organs are present in the same individual) most earthworm species reproduce by cross-fertilisation, although some are parthenogenetic (Reproduction in which the ova develops without being fertilised by a spermatozoa, hence it involves only one parent).

Do earthworms live in groups? What is the collective noun for a group of earthworms?

Certain earthworm species tend to be associated with one another and usually such associations result from some characteristic of the habitat (e.g. availability of food resources). Individual earthworm species also have relationships with many other organisms including, micro-organisms, invertebrates and vertebrates.

As far as I am aware there is no collective noun for a group of earthworms, but I propose a slither of earthworms may be an apt phrase to use.

What is the life span of an earthworm ?

Researchers have estimated that the potential life-span of earthworms (Lumbricids) under field conditions is 4-8 years. Under laboratory conditions the black headed worm (Aporectodea longa) has been kept for over 10 years, the brandling/tiger worm (Eisenia fetrida) for 4.5 years and the lobworm/nightcrawler (Lumbricus terrestris) for 6 years (Korschelt, 1914).

How many species of earthworm are there?

Worldwide there are approximately 3000 species of earthworm of which 28 species (not including introduced species) are found in the UK.

Each species can be ascribed to one of three major groupings. The first group (litter dwellers) encompasses those species that inhabit the surface organic layers of the soil and may also occur within compost heaps. These include common species such as Eisenia fetida (the brandling or tiger worm) and Dendrobaena veneta (another striped worm).

Earthworms which fall within the other two ecological groups (deep burrowers and shallow workers) do not require such a high level of organic matter and thrive within mineral soils. However their life cycle, although passing through the same 3 stages (...adult - cocoon - hatchling...), is less prolific than that of litter dwelling worms. Deep burrowing species such as Lumbricus terrestris (the lob worm) and Aporrectodea longa (the black-headed worm) usually require a deep, mature soil with a supply of surface organic matter. Smaller shallow working species such as Allolobophora chlorotica (the green worm) or Aporrectodea caliginosa (the grey worm) need less depth of soil and require a soil with a mixture of organic and inorganic components.

Is a ragworm an earthworm?

Although both belong to the Phylum Annelida a ragworm is not an earthworm. The ragworm (genus Nereis) belongs to the annelid class Polychaeta (many bristles) a large group of 5,500 species of marine worms with segmented appendages and bristles. The earthworm belongs to the annelid class Oligochaeta (few bristles), species of this class are predominantly freshwater and terrestrial with no appendages.

Can earthworms survive in the human gut like a tape worm?

Tapeworms belong to the class Cestoda and are endoparasites that live in the small intestine of vertebrates. As such they have numerous adaptations that allow them to survive in the hostile environment of the small intestine. Earthworms do not exhibit any such adaptations and unless they pass directly through the gut they would be broken down by digestive acids.

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Are earthworms asexual?

The majority of earthworm species are hermaphrodites possessing separate testes and ovaries that function simultaneously and reproduce by cross-fertilisation. However, some species can reproduce parthenogenetically (Reproduction in which the ova develops without being fertilised by a spermatozoa, hence it involves only one parent).


What type of earthworm is best suited for use in my compost bin?

Litter dwelling species are best suited for use in your compost bin. Commonly used species include the tiger worm / brandling (Eisenia fetida), Dendrobaena veneta aonther striped worm and the red worm (Lumbricus rubellus).

Why is the New Zealand flatworm such a threat to earthworms in the UK?

The New Zealand flatworm (Arthurdendyus triangulatus) is not native to the United Kingdom and was first recorded in the UK in 1963. This species is now widely distributed throughout Scotland and can also be found in Northern England. It is carnivorous and feeds mainly on earthworms; however their impact on earthworm populations is as yet inconclusive.

Do earthworms have any medical uses?

Research in the USA is currently looking into earthworms' anti-inflammatory properties for treating arthritis and other joint ailments and is also investigating other medical uses associated with earthworms' ability to burrow through and eat soil without being attacked by bacteria.

Earthworms have also been used in Chinese medicine as an aphrodisiac and fertility treatment.

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