Milyeringa veritas (Eleotridae), a remarkably versatile cave fish from thearid tropics of northwestern Australia

The blind cave gudgeon Milyeringa veritas is restricted to groundwaters of Cape Range and Barrow Island, northwestern Australia. It occurs in freshwat er caves and in seawater in anchialine systems. It is associated with the o nly other stygobitic cave vertebrate in Australia, the blind cave eel, Ophi sternon candidum, the world's longest cave fish, and a diverse stygofauna c omprising lineages with 'tethyan' tracks and widely disjunct distributions, often from North Atlantic caves. The cave gudgeon inhabits a karst wetland developed in Miocene limestones in an arid area. There is an almost comple te lack of information on the basic biology of this cave fish, despite it b eing listed as threatened under the Western Australian Wildlife Conservatio n Act. Allozyme frequencies and distributions indicate significant populati on sub-structuring on the Cape Range peninsula such that the populations ar e essentially isolated genetically suggesting that more than one biological species is present. Further, they suggest that the vicariant events may ha ve been associated with a series of eustatic low sealevels. Analysis of int estinal contents indicates that they are opportunistic feeders, preying on stygofauna and accidentals trapped in the water, at least at the sites samp led which were open to the surface, a conclusion supported by the results o f stable isotope ratio analysis. The gudgeons are found in freshwater caves and throughout deep anchialine systems in which they occur in vertically s tratified water columns in which there is a polymodal distribution of water chemistries (temperature, pH, salinity, dissolved oxygen, redox, dissolved inorganic nitrogen series, hydrogen sulphide).