Stygofauna from Cape Range peninsula, Western Australia: Tethyan relicts

WA Museum Records and Supplements | Updated 9 years ago

Abstract: The biology and distributions of the stygofauna from Cape Range peninsula are reviewed. This stygofauna comprises seven elements: two species of teleost fish, the blind gudgeon Milyeringa veritas Whitely, 1945 (Perciformes: Eleotrididac), and the blind cave eel Ophisternon candidum (Mees, 1962)(Synbranchiformes: Synbranchidae); and five species of malacostracan crustacean, Stygiocaris lancifera Holthuis, 1960 and Stygiocaris stylifera Holthuis, 1960 (Decapoda: Atyidae), Halosbaena tulki Poore and Humphreys, 1992 (Thermosbaenacea), and two undescribed species of Amphipoda. All seven elements are macrofaunal and exhibit troglobitic morphology. Meiofaunal elements (protists, turbellarians, nematodes, oligochaetes, copepods, and acarines) are cited. The gastropod Iravadia sp. is recognized as possibly a marine stygophile.

The seven species are known only from the limited fresh groundwaters of the area. The atyids, thermosbacnaccan, one amphipod and both species of fish are widespread in subterranean fans of freshwater about stream courses of the coastal plains; in marked discontinuity, the eriopisid amphipod from pools in four caves on Cape Range occurs at elevations of 110 m or higher above sea level. These cave pools are probably perched. Possible evolutionary, ecological and physical causes for the discontinuity in distribution betwccn the coastal and Range species are discussed. Antecedents of all elements of the Cape Range stygofauna are regarded to have evolved in the Tethys Sea, and invasion into groundwaters of the peninsula is considered to have occurred in situ throughout the whole sedimentary basin wherein the peninsula developed. Two phases of invasion are proposed: the first concomitant with initiation in uplift of the Cape Range anticline involved the thermosbaenaccan and eriopisid Range dwelling amphipod from marine ancestors; the second phase at a much later time involving the two species of fish and atyids from fresh waters of the Ashbunon River, then much closer to Cape Range than it is now.