Class Oligochaeta
Phylum Annelida
Worldwide, approximately 6,000 species of earthworms are described in 20 families. In Australia, earthworm populations consist of native and introduced species from a total of eight families: Moniligastridae, Glossoscolecidae, Lumbricidae, Ocnerodrilidae, *Acanthodrilidae, *Octochaetidae, Benhamiidae, *Megascolecidae, and Eudrilidae. Australian natives are estimated to total 1,000 species belonging to three of these families (marked with an asterisk), while the 80 or so introduced species, have representatives from all eight.
Earthworms are found in soils, leaf litter, under stones and logs, and sometimes in trees. They tend to be more numerous in the wetter, more heavily vegetated areas. Native species are primarily found in undisturbed areas but some can tolerate cultivation and a few species persist in deserts.
The Lumbricidae are native to Britain and other northern temperate countries in North America and Asia. Today this family is known from all over the world and such earthworms are called 'peregrine' species because of their great ability to travel from place to place. Once introduced into a new area, they have an amazing ability to breed rapidly and colonise their new home, often surpassing the original native species.
The Lumbricidae are distinguishable from other earthworm families in having the openings of the male reproductive ducts on segment 15 (counting from the head end), well in front of a glandular swelling on the skin, called the clitellum. (The segments are the rings, separated by grooves, which divide the body from head to tail.) The clitellum is responsible for producing the envelope, or cocoon, in which the eggs are deposited.
The lumbricids were introduced to Australia during the last two centuries (since European settlement). They may have come here in soil around introduced fruit trees and shrubs brought here by the early settlers. For example, Aporrectodea caliginosa is one of the commoner pasture worms that are washed on to roadways after heavy rains. Another introduced species is the deep-burrowing Lumbricus terrestris which, although known only from northern Tasmania, is the species most often used in schools as a typical example of an earthworm - in preference to the many available native earthworm species. A smaller, reddish species that frequents compost heaps is Eisenia fetida which is sometimes called the "tiger worm"; because of its ringed appearance.
These are just three examples of the many 'peregrine' earthworms, each with its own unique characteristics.
Australian native worms are drawn from these three families. The first two are more common in the tropics and arid regions, while megascolecids are more common in the southern states. In general, Australian natives can be recognised by counting the number of segments in front of the clitellum (a magnifying glass is needed). If the clitellum starts on segment 14, the worm will either be a native species or one of the introduced tropical species of these families.
Some Australian native earthworms grow to an enormous size. Besides the well-known 'Gippsland Giant', Megascolides australis, cited in the Guinness Book of Records at 3 metres, others also grow large. A species of Digaster found near Kyogle in north-eastern New South Wales, often grows to a length of more than 150 cm and is as thick as a garden hose. Notoscolex grandis from Burrawang, eastern New South Wales, has been recorded as reaching a length of 100 cm. Large worms also occur in Queensland through to Tasmania, and these are all different species.
Many gardeners in New South Wales may have seen fairly slender but muscular, light-brown earthworms, 10 cm -15 cm long, which, when brought to the surface, move off rapidly with an eel-like motion, bending the body vigorously from side to side. These worms are either Amynthas corticis or Amythas gracilis which are the most common introduced megascolecids found around the world. They can be identified by the presence of a single female pore in the middle underside of the fourteenth segment, with a ring-shaped clitellum embracing this segment as well as segments 15 and 16. Also, the setae are arranged in a ring around each segment, and not merely on the undersurface as in lumbricids and some other megascolecids. These worms are capable of parthenogenesis, or 'virgin birth' (which also occurs in many rival species of lumbricids): a feature of obvious advantage to a potential pioneer.
Only a few native Australian earthworms have been successfully cultivated commercially (for example Anisochaeta dorsalis, sold in bait shops), and they are rarely considered for their benefit in increasing soil fertility or for supplying teaching institutions with study material.
Revised by: Dr Rob Blakemore
Yokohama National University, Japan
April 2005
Copyright © Australian Museum, 2003
This page: http://www.amonline.net.au/factsheets/recognising_earthworms.htm
