Amblyopsis

Amblyopsis is a genus of small (up to 11 cm or 4.3 in long) fish in the family Amblyopsidae that are endemic to the central and eastern United States.

[1] Like other cavefish, they lack pigmentation and are blind.

[3] Uniquely among fish, Amblyopsis brood their eggs in the gill chambers (somewhat like mouthbrooders).

[4] It was formerly incorrectly speculated that the same brooding behavior existed in other genera in the family and in the pirate perch (Aphredoderus sayanus).

[4][5] During the Pleistocene period, the modern Ohio river was a barrier of dispersal and created a great genetic variation, leading to two phylogenetically distinct lineages from the species Amblyopsis.