Stygofauna are any fauna that live in groundwater systems or aquifers. They can be crustaceans, worms, gastropods, beetles, mites and fish.
Never seeing the sun, they have no circadian rhythms. They grow slowly, don’t have many young, live long lives and stay close to home. Some are from extremely old lineages, with ancestors dating back to Gondwana and Pangaea or the Tethys Ocean, 200 million years ago. Some display a close relationship with species from other continents which indicates that their ancestors came from a time before the break-up of the
It is because of their characteristics born of their low-energy environment, and their incredible age, a lot of stygofauna species are extremely rare and localised.
Stygofauna contribute important ecosystem services by creating a nutrient cycle, and have been recognised as indicators of groundwater health. The stygofauna are small enough to wander among grains of sand in the sandstone aquifers, purifying the water by eating bacteria – playing a similar role to earthworms in soil.
Stygofauna are amazing because they are an inconspicuous but important component of World biodiversity. They represent outstanding examples of adaptation and ongoing evolutionary processes, and contain many ancient lineages of high scientific value and conservation significance.
We know stygofauna are not very mobile, so they make poor colonisers. This means that if all the creatures in one locality are wiped out, it is unlikely that others will quickly replace them.
Stygofauna are vulnerable to extinction from environmental changes and human impacts.
The Pilliga Sandstone Aquifer has been found recently to contain rare species of stygofauna. A survey of 22 sites within the Pilliga Sandstone aquifer conducted in 2016-17 reported a total of eleven taxa of invertebrates, which included ten families from five orders of stygofauna. The results showed stygofauna exist across the entire area.
They are classified as of High Ecological Value in the Pilliga, as the area is covered by the Lowland Darling Aquatic Endangered Ecological Community, listed under the Fisheries Management Act 1994.