Subterranean Fishes of the World

6931

2024

The blind cave eel (Ophisternon candidium) is classified as endangered by the IUCN Red List of Threatened Species and is one of three Australian stygobitic fish species. This species is rarely collected by net hauling (the most common stygofauna sampling method used in Australia), and the use of Environmental DNA (eDNA) has been invaluable in determining species’ distribution and persistence. The use of eDNA however, is not without its limitations. In a natural system, DNA commonly degrades quickly, due to numerous factors including microbial processes, water chemistry, ultraviolet light and heat. These factors vary across environments, and so the rate of DNA decay will be different in different systems. Time until eDNA is undetectable ranges from hours to weeks, and little is known about how long eDNA persists in subterranean environments. In September 2023, during a stygofauna monitoring survey (not targeting blind cave eel) conducted in the Robe Valley (Western Australia) on behalf of Rio Tinto, a live specimen was collected from a groundwater bore using a 70mm haul net. The specimen was held in groundwater from the collection site for approximately 15 minutes, after which it was released back into the bore. This groundwater was retained to conduct an ad hoc eDNA degradation trial. Using passive eDNA sampling, samples were taken at different time intervals, over a 72-hour period. Eel eDNA was targeted using two approaches, both focusing on the 16S gene region: a metabarcoding approach, and a species-specific probe, amplified using qPCR. Eel eDNA was detected at all time intervals, in all replicates, using both approaches. Noting limitations to the experimental design, considering how infrequently blind cave eel specimens have been collected (eight specimens to date from the Robe Valley catchment) the results of this study provide the first insight into longevity of blind cave eel eDNA and can help interpret, movement of DNA in groundwater habitats and the distribution of this elusive species

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26th International Conference on Subterranean Biology and 6th International Symposium on Anchialine Ecosystems: Cagliari 9-14 Sept 2024