Queensland Lungfish - Physical Description

Physical Description

Queensland lungfish are olive-green to dull brown on the back, sides, tail, and fins and pale yellow to orange on the underside. They have been described as having a reddish colouring on their sides which gets much brighter in the males during the breeding season. This colouration is the only distinguishing sexual characteristic of the lungfish. They have stout, elongated bodies and flattened heads with small eyes. The mouth is small and in a subterminal position. The lungfish can grow to a length of about 150 centimetres (4.9 ft), and a weight of 43 kilograms (95 lb). It is commonly found to be about 100 centimetres (3.3 ft) and 20 kilograms (44 lb) on average. Both sexes follow similar growth patterns, although the females grow to a slightly larger size. They are covered in slime when taken from the water.

The skeleton of the lungfish is partly bone, and partly cartilaginous. The vertebrae are pure cartilage while the ribs are hollow tubes filled with a cartilaginous substance. The body of the lungfish is covered with large, bony scales. There are ten rows on each side, grading to small scales on the fins. The scales are each embedded in their own pocket, and overlap extensively, such that vulnerable areas of the body are covered by a thickness of at least four scales. Two unusually large and thick interlocking scales cover the back of the head where the bony skull is thin. They have powerful diphycercal tails that are long and paddle-shaped. The pectoral fins are large, fleshy, and flipper-like. The pelvic fins are also fleshy and flipper-like and situated well back on the body. The dorsal fin commences in the middle of the back and is confluent with the caudal and anal fins.

The dentition of the lungfish is unusual: two incisors, restricted to the upper jaw, are flat, slightly bent, and denticulated on the hind margin. These are followed by dental plates on the upper and lower jaws.

Juveniles have different body proportions than mature adults. The head is rounder, the fins are smaller, and the trunk is more slender. The mouth is initially terminal, but shifts back as the fish grows. The dorsal fin typically reaches to the back of the head in young juveniles, and gradually moves caudally until it only extends to the mid-dorsal region in adults. They show a gradual change in body form as they develop, but there is no externally detectable metamorphosis and no obvious point at which they can be termed adult. As a juvenile the lungfish is distinctly mottled with a base colour of gold or olive-brown. Patches of intense dark pigment will persist long after the mottling has disappeared. Young lungfish are capable of rapid colour change in response to light, but this ability is gradually lost as the pigment becomes denser.

The lungfish is reputed to be sluggish and inactive, but it is capable of rapid escape movements with the use of its strong tail. It is usually quiet and unresponsive by day, becoming more active in the late afternoon and evening.