Stygofauna and Troglofauna

Within the underground karst ecosystems, such as caves and caverns, stygofaunal and troglofaunal species yield information about evolution of life on earth, bio-geography and changing climates in Australia spanning from the late Palaeozoic era to the present time (Humphreys & Danielopol, 2005; DEWHA, 2008). As subterranean, cave-dwelling organisms, stygofauna and troglofauna have adapted to living in isolated conditions underground over millions of years.

Stygofauna

Unlike the troglobites, stygofaunal species which date from pre-Gondwana, solely exist within aquatic groundwater environments. Mainly consisting of subterranean aquatic specialists, Crustaceans hold the greatest biogeographical significance as they form the richest diversity of stygofaunal invertebrates including amphipods, copepods and ostracods (DEWHA, 2008). Closely related to ancient species that inhabited areas of the Caribbean and the Canary Islands, off the coast of Africa, stygofaunal species have evolved over millions of years to carry the most beneficial traits for their isolated environment. Similar to troglofauna, stygofaunal species can be divided into stygophiles (species not restricted to either surface or subterranean environments), stygoxenes (occasionally dwell in cave environments, but do not complete their life cycle within them) and stygobites (species that are obligately dependent on the cave environment and complete their full life cycle within them), dependent on their life histories (Lopes et al. 1999)

Troglofauna

Troglofaunal species can be characterised as organisms which live above the water table within cave structures. Rare within their environment, terrestrial and amphibious troglofauna (Hamilton-Smith et al., 1998) include a variety of beetles, spiders, cockroaches, slaters, crickets, scorpions and millipedes. Closely related to species found in Australia’s cool temperate forests, these species once formed a small part of an extensive leaf litter community within a Miocene tropical rainforest. However, having been isolated underground over millions of years due to climatic change, they have evolved and adapted to their deep cave habitats (DEWHA, 2008). Troglofaunal adaptations can include a heightened sense of touch, smell or hearing with a loss in sight as this sense is often under-used in the dark environment (Chapman, 1982). Dependent on their life-histories, troglofauna can be characterized into three sub-sections: troglophiles (species that may complete their life cycles in the cave systems, but can also survive in above ground habitats); trogloxenes (species that only use the cave systems for shelter, but does not complete their life cycle within them); and troglobites (species that cannot survive outside the cave environment and therefore complete their whole life cycle within the cave system) (Chapman, 1982). As most troglofaunal species are dependent on the cave environments for at least part of their life-cycles, most species are sensitive to small environmental changes as caves tend to be isolated and mostly closed off (Poulson & White, 1969). Floodwaters can be one of the biggest threats to troglofaunal species as they can dramatically change the environment by reducing the availability of food, oxygen and space along with the connectivity between the caves (Lamoreux, 2004).

Reseach needed

Both stygofauna and troglofauna are rare and some species are on the brink of extinction. Further exploration into the communities that live within the Gnaraloo cave systems would add to work being undertaken on the Exmouth Peninsula, helping build a fuller picture on species distribution within the area and climatic changes across Australia since the Miocene period (Humphreys & Collis, 1990; Gillieson, Humphreys & Spate, 2006).

The information was compiled by Karen Hattingh, Simone Bosshard, Tessa Concannon, Tess DeSerisy, Heather Shipp and Megan Soulsby, 2017/18

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