Australian Lungfish

1 Overview

The Australian lungfish (Neoceratodus forsteri) — also called the Queensland lungfish — is the largest of the living lungfishes and a genuine ‘living fossil’ that shared the Earth with the dinosaurs roughly 300 million years ago. It is a temperate, bottom-dwelling fish native to eastern Australia.

Taxonomy — Kingdom: Animalia; Phylum: Chordata; Class: Sarcopterygii (lobe-finned fishes); Order: Ceratodontiformes; Family: Neoceratodontidae; Genus: Neoceratodus; Species: Neoceratodus forsteri.

Key facts: Adult length 100–170 cm (39–67 in), weight up to about 10 kg; temperament peaceful; preferred temperature 19–29°C; pH 6.5–8.0; hardness 12–18°N (dGH); bottom water layer; reproduction oviparous (egg-laying). Also known simply as the ‘lungfish’.

Lifespan note: a few popular care sheets (including the source article for this profile) list the lifespan as ‘2–3 years’ — this is a documented error. The Australian lungfish is among the longest-lived of all fishes; well-kept captive individuals have been recorded at 65–90+ years, and wild fish likely live several decades. The figure shown in the info box reflects the scientifically documented range, not the erroneous source value.

2 Appearance

A remarkable trait of the Australian lungfish is that it can breathe with a true lung when dissolved oxygen in the water runs low — unlike almost all other fish. In hot summers, when ponds become oxygen-starved and other fish die in large numbers, the lungfish survives by gulping air at the surface.

It is the largest of the modern lungfishes. Reaching about 125 cm (49 in) and up to 10 kg, its body is elongate and spindle-shaped, covered with large, thin, rounded scales. The pectoral and pelvic fins are lobe-like with fleshy, scaled bases; the dorsal, caudal and anal fins merge into one continuous fin. The swim bladder (lung) is long and unpaired, internally divided into many paired air sacs (alveoli). It has five well-developed gill pairs. Endemic to Queensland, Australia, it can breathe with gills and lung together, or use either alone.

Often called a living fossil, the lineage of this fish reaches back roughly 300 million years to the age of the dinosaurs. Because it has lungs and can breathe air, it is regarded as an important link in the chain of fish-to-tetrapod evolution. It belongs to the order Ceratodontiformes, family Neoceratodontidae, genus Neoceratodus.

3 Natural Habitat & Conservation

Despite its primitive air-breathing anatomy, the Australian lungfish cannot live out of water for long. It is found mainly in the rivers of Queensland, Australia, favouring slow-moving, vegetated rivers and ponds.

During summer, when ponds are severely oxygen-depleted and other fish die off, the lungfish survives by breathing air with its lung; it cannot, however, fully leave the water. In autumn, fresh oxygen-rich water returns and it resumes gill breathing. Its spawning season is long, peaking in September–October; the eggs are large (6–7 mm), wrapped in a non-sticky gelatinous membrane and laid among plants, with some sinking to the bottom. Unlike other living lungfishes, its juveniles have no external gills and no adhesive organ — fry feed on filamentous algae, adults on molluscs, crustaceans, insect larvae and worms.

Important: The Australian lungfish is a protected species in Queensland, Australia, and is not part of the commercial ornamental aquarium trade. This profile is provided for educational reference only; it should never be kept, sold, or imported as a pet fish.

4 Diet & Feeding

Adults are carnivorous bottom-feeders, eating molluscs, crustaceans, insect larvae and worms. In the wild they forage along vegetated riverbeds and among submerged structures.

As human awareness of this extraordinary air-breathing fish has grown, scientists have found its breeding and habitat waters steadily shrinking; it now faces a real risk of extinction and is a protected animal in Australia. Conservation of its native Queensland river systems (the Burnett and Mary basins) is essential to the species’ survival.