Postojna Cave Herald Snail (Zospeum spelaeum spelaeum), empty shells measuring 2 to 3 mm in length accumlated on cave wall from receding drainage water. All known Zospeum have lost visual orientation and are considered true eutroglobionts. Troglobionts or Eutroglobionts are animals that live in caves and are unable to live outside of it. Troglobionts usually have troglomorphic adaptions, which means they have adapted to the special environment. Information on their biology is scarce, but species seem to possess a limited active movement and to prefer muddy and permanently wet subterranean microhabitats, as generally found along the drainage system of a cave. Dispersal may primarily occur via passive transportation (e.g. by water or larger mammals). Postonja Cave, Slovenia. March.