The fountain darter (Etheostoma fonticola) is a species of freshwater ray-finned fish, a darter from the subfamily Etheostomatinae, part of the family Percidae, which also contains the perches, ruffes, and pikeperches. It is found in the headwaters of only two rivers in Texas, United States, the Comal River, and the San Marcos River. It is generally smaller than long and feeds on small invertebrates. It is a federally listed endangered species of the United States
Status
They primarily occupy the sandy tops of lesser-flowing springheads or flat rock surfaces absent of rooted plants or decaying plant matter, and spawn within the vibrantly abundant and healthy vegetation that thrives in these unique, pristine, spring-fed river systems. An extra worry for the future of fountain darters is the parasitic, non-native trematode (Centrocestus formosanus), whose impact on the darter population is not yet known. As of 2011, only the Comal population is seriously affected by the parasite.