Overview
Eiselt’s Caecilian (Atretochoana eiselti), often referred to colloquially as the man-made caecilian or Brazilian caecilian, is a bizarre aquatic amphibian holding the scientific record as the largest known lungless tetrapod in the world. Originally documented from a single museum specimen in Vienna, this elusive species gained global scientific prominence in 2011 when living wild populations were rediscovered thriving in the deep waters of the Brazilian Amazon.
Biology and Physical Characteristics
Atretochoana eiselti possesses an elongated, limbless body colored in uniform slate-gray to purplish-brown, lined with prominent annular skin grooves. Its skull is remarkably broad and flattened, featuring sealed nostrils (choanae) and a wide, fleshy mouth. Most extraordinarily, it completely lacks lungs; respiration occurs entirely through cutaneous gas exchange across its highly vascularized, loose skin folds and capillaries, augmented by a distinctive dorsal fleshy fin fold along its posterior body.
Behavior and Ecology
Strictly aquatic, Eiselt’s Caecilian inhabits deep, warm, turbid river channels where water currents remain moderate to fast. It navigates dark riverbeds using sensitive tactile and chemical cues along its snout, as its eyes are reduced and covered by a translucent layer of skin. It burrows through muddy substrates and glides with rhythmic lateral undulations, hunting small benthic prey such as shrimp, aquatic insect larvae, and small bottom-dwelling fish.
Conservation and Human Impact
Listed as Data Deficient by the IUCN, Atretochoana eiselti remains one of the least studied large vertebrates in South America. Ongoing hydroelectric dam projects on the Madeira River and gold mining runoff that alters river siltation represent potential ecological threats to its specialized riverbed habitat. Environmental scientists continue targeted surveys across the Amazon and Tapajós basins to evaluate wild population health.
Interesting Factoid
Reaching over 30 inches in length, Eiselt’s Caecilian is the largest lungless four-limbed vertebrate descendant on Earth, absorbing all its oxygen directly through its loose, vascular skin.
Last updated: October 2026