Reductions of flows resulting from drought and water withdrawals threaten the Fountain Darter (Etheostoma fonticola) in the headwater springs that feed the San Marcos and Comal Rivers, Texas. These are the only two places in the world this species is found. It uses dense aquatic plants and algae as habitat. It is severely threatened by the loss of vegetation caused by an exotic snail and afflicted by a parasitic non-native trematode whose life cycle uses the exotic snail as a host.
