You searched for: “troglobiont
troglobiont (s) (noun), troglobionts (pl)
1. An organism found only in caves or subterranean passages: Jack, the scientific spelunker (cave explorer), was studying the plant troglobiont which was found in the deep recesses of the cave.
2. An animal living entirely in the dark parts of caves: Many troglobionts have adapted to life in caverns and no longer have functional eyes; in other words, they are blind.