Giant Gippsland Earthworm

Tagged: animal

Megascolides australis

One of the largest earthworms in the world, the giant gippsland earthworm was discovered in 1878. Its large size and secretive habits have made it vulnerable to changes in land use resulting from the development of agricultural land from natural forest. The giant Gippsland earthworm belongs to the Phylum Annelids, the segmented worms, which includes earthworms, rag worms, and leeches. Named after the area of Australia that is its home, it is found only in Gippsland, a fertile region of southeastern Victoria that extends along the coast from Melbourne to the New South Wales border. The giant Gippsland earthworm lives in permanent and elaborate burrows, spending all its life underground. There it feeds on the roots of plants and on other organic matter in the soil. Most earthworm species deposit their waste material as obvious casts on the surface, but this species leaves its cast material below ground. Result of its exclusively underground life the giant Gippsland earthworm is difficult to study. Consequently, many aspects of its biology are unknown. We do know that its body is divided up into between 300 to 500 visible segments. The head and front third of the body are a dark purple color; while the remainder, behind the “saddle,” is a pinkish-gray. Giant Gippsland earthworms are not easily kept in captivity, and because of their large size and fragility they are easily damaged or killed by scientists and farmers alike.

Patchy Distribution

The distribution of the giant Gippsland earthworm was previously much wider than it is today. When European settlers arrived in the 18th century, they transformed large areas of native forest into pasture for the dairy industry. The disturbances associated with this proved very damaging to the worms. Today giant Gippsland earthworms tend to be restricted to steep hillsides and valleys where the soils cannot be plowed. Any activities that affect the moisture content and drainage of the soil can also be bad news for the worms. Building roads and dams, trenching, and laying cables are all damaging activities. Natural seasonal fluctuations of moisture content govern the normal movement of the worms within the soil. Recent surveys of southern and western Gippsland have shown that the giant earthworm is restricted to about 40 square miles (100 sq. km) of land in an area bounded approximately by Loch, Korumburra, and Warragul. Much of this land is unsuitable, and the giant earthworm’s distribution is very patchy. The population density of the adult worms within the acceptable areas is usually low, about two individuals per 35 cubic feet (two per cubic meter). The worms are mostly found in blue-gray clay soils on flats by the banks of streams or along ditches and watercourses where the slopes face a southwesterly direction. Like all earthworms, the giant Gippsland worms have beneficial effects on the quality of the soil in which they live, contributing to an increase in its organic content and assisting aeration and increasing fertility. The giant Gippsland earthworm has become part of the folklore of southern Gippsland, and many landowners speak with pride about its presence on their properties.

Conservation

Conserving the giant Gippsland earthworm is difficult. Retaining natural vegetation alongside streams as well as on steep slopes and in valleys and keeping out livestock by fencing the remaining earthworm habitats are both thought to be helpful measures. However, such strategies rely heavily on the cooperation of private landowners and farmers who may need help in identifying the parts of their properties that accommodate the giant earthworms. One issue that has recently made this more difficult is the splitting up of larger properties into smaller ones used for small scale farming.

DATA PANEL

• Family: Megascolecidae
• World population: Unknown
• Distribution: Restricted to about 40 square miles (100 sq. km) of land in Gippsland, Victoria, Australia
• Habitat: Burrows in organically rich soils
• Size: Length: 31 in (80 cm); diameter 0.8 in (2 cm)
• Form: Typical segmented worm; a definite head and 300-500 segments each with chateau (bristles); well-developed respiratory and vascular system
• Diet: Plant tissue and organic matter in soil
• Breeding: Worms are hermaphrodite, but 2 individuals are required for fertilization to occur. Mating takes place in spring and early summer. Individuals lay a single amber-colored egg capsule containing 1 embryo, which takes about 12 months to hatch. The earthworms are presumed to reach adulthood about 4.5 years after hatching. Adults may be long-lived.

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