Key to Australian Freshwater and Terrestrial Invertebrates
Phylum Annelida
Class Clitellata
Family Enchytraeidae
Common names: pot worms, microdriles
Overview
Enchytraeids are generally small, pale coloured worms with simple-pointed chaetae often arranged ventro-laterally and laterally. The family is found worldwide and includes the �ice worm� genus Mesenchytraeus, which is found in glaciers in Alaska and is unable to survive temperatures above 5�C. In Australia, enchytraeids are poorly studied and it is likely the described diversity is only a fraction of what is present. Most species are less than 25 mm long, with a diameter of 0.7 mm - 1.5 mm.
Distribution and diversity
Worldwide there are around 700 species of enchytraeids in 28 genera. 39 species in eight genera from a wide range of habitats have been described from Australia. Six genera (Enchytraeus, Grania, Randidrilus, Stephensoniella, Lumbricillus and Marionina) occur in marine habitats. Fridericia occurs in damp soil in south-western Australia whist Cognettia species are found in peat bogs. There is also a species of Marionina (M. normani) found in freshwater and some species of Grania and Lumbricillus are reported from euryhaline environments.
Life cycle
Depending on the species, enchytraeids are either sexually reproducing hermaphrodites or reproduce by asexual fragmentation (new heads and tails formed after the body splits into fragments). The normal mode of reproduction is thought to be mutual fertilisation (the exchange of sperm between two worms). When reproducing sexually, the eggs are laid in a cocoon secreted by the clitellum. The fertilised eggs develop directly into small, but fully formed worms that emerge and grow continuously until adulthood.
Feeding
Enchytraeids feed on microorganisms, bacteria, fungi, microalgae and protists.
Ecology
Enchytraeidae inhabit a wide range of freshwater and brackish habitats, from stream and lake beds (including salt lakes) to peat bogs, and are common members of terrestrial soil communities, particularly that rich in organic matter. Terrestrial Enchytraeidae are considered useful in soil toxicity testing. They are important in the breakdown of organic materials and nutrient cycling and their feeding behaviour also mixes the sediment, keeping it aerated and providing oxygen for other organisms. Some species are commercially bred for the aquarium trade as fish food.
