Australian Lungfish

Overview

The Australian Lungfish (Neoceratodus forsteri), celebrated throughout Queensland as the Queensland lungfish or Burnett salmon, is an extraordinary, archaic sarcopterygian (lobe-finned) fish and one of the most famous ‘living fossils’ on Earth. Belonging to the monotypic family Neoceratodontidae, this ancient creature is the sole surviving representative of a fossil lineage that flourished over one hundred million years ago during the Early Cretaceous, remaining virtually unchanged in its skeletal anatomy. Famous for possessing both functional gills and a true vascularized lung, it provides a living anatomical window into the epic evolutionary transition of vertebrates from water onto land.

Ecologically, Neoceratodus forsteri operates as a long-lived, slow-moving benthic predator and nutrient processor in subtropical river ecosystems. Inhabiting deep, still river waterholes lined with dense beds of submerged ribbonweed (Vallisneria), it forages nocturnally along the riverbed, consuming freshwater mussels, snails, burrowing crayfish, and worms. Its grinding tooth plates crush hard-shelled mollusks, accelerating nutrient cycling in sluggish river reaches, while its massive physical presence helps shape benthic substrate architecture.

Biology and Physical Characteristics

Neoceratodus forsteri displays a heavy, elongated, torpedo-shaped body covered in massive, overlapping, diamond-shaped bony scales that can measure up to five centimeters across. Its coloration is olive-green to dull greyish-brown above, transitioning to a pale salmon-pink or creamy yellow on the belly. Its pectoral and pelvic fins are fleshy, paddle-like, and muscular (lobate), supported by an internal bony skeleton homologous to the limbs of land-dwelling tetrapods; the fish can use these sturdy lobed fins to prop itself up and ‘walk’ along river gravel. Its tail is diphycercal, continuously fused with the long dorsal and anal fins into a broad, paddle-like fin. While it breathes primarily through gills like typical fish, when seasonal droughts cause river pools to become stagnant and deoxygenated, the lungfish surfaces every thirty to sixty minutes, inhaling atmospheric air through its nostrils into a large, highly vascularized single lung with a loud, bellows-like acoustic sigh.

Behavior and Ecology

Australian lungfish are sluggish, solitary, and largely nocturnal dwellers that spend daytime hours resting motionless among sunken tree logs and weed beds. Unlike African and South American lungfishes, which can burrow into mud and form dry cocoons during droughts, the Australian lungfish cannot aestivate; it must remain in water to survive, relying on its lung only to supplement gill respiration during hot, hypoxic summers. Spawning occurs between August and November: courting pairs swim closely through dense submerged aquatic plants, where the female deposits hundreds of large, gelatinous, emerald-green eggs resembling frog eggs onto aquatic weed fronds. The eggs hatch after three to four weeks into tiny tadpole-like larvae that lack external gills and develop with remarkable slowness, taking over fifteen years to reach sexual maturity.

Conservation and Human Impact

The Australian Lungfish is classified as Endangered on the IUCN Red List and listed under CITES Appendix II. Endemic to just two river basins in Queensland (the Mary and Burnett rivers), wild populations face severe threats from water impoundments, agricultural dams, and weir construction, which drown shallow macrophyte spawning beds, alter water temperatures, and cause high egg mortality. A historic specimen named ‘Methuselah’, brought to the Steinhart Aquarium in San Francisco in 1938, lived to be over ninety years old, becoming famous as the world’s oldest living aquarium fish.

Interesting Factoid

The Australian lungfish is an unchanged dinosaur fish that breathes with a real lung: it has been swimming in Australian rivers since before the continents broke apart, and when stagnant river pools run out of oxygen in summer, it sticks its snout out of the water and takes a breath of air with a loud puff that sounds like a person taking a deep sigh.