Lungfish

The Australian Lungfish has a long, heavy body with large scales. It has small eyes and paddle-like pectoral fins and pelvic fins. Its dorsal fin starts midway along the back and is continuous with the caudal and anal fins.
This species is usually olive-green to brown on the back and sides with some scattered dark blotches, and whitish ventrally.
It grows to about 1.5 m in length and over 40 kg. The Shedd Aquarium's Australian Lungfish, affectionately known as 'Granddad' (see top image) is over 80 years old, and is possibly the oldest fish in captivity.
The Australian Lungfish has a single lung, whereas all other species of lungfishes have paired lungs. During dry periods when streams become stagnant, or when water quality changes, lungfishes have the ability to surface and breathe air. When the Australian Lungfish surfaces to empty and refill its lung the sound is reportedly like that of the "blast from a small bellows". Under most conditions, this species breathes exclusively using its gills.
Food items include mainly frogs, tadpoles, small fishes, snails, shrimp and earthworms. It will also eat plant material. The eyesight of the Australian Lungfish has been reported to be poor and the location of prey was thought to be based on the sense of smell rather than sight. The recent work of Watt et al has shown that the Australian Lungfish can use electroreception to locate hidden prey. Their research on the anatomy of this species has shown the presence of organs similar to those used for the detection of electric signals in other fishes, such as sharks.
The Australian Lungfish is normally found in still or slow flowing pools in river systems of south-eastern Queensland. It occurs naturally in the Burnett and Mary River systems although has been introduced into other rivers and reservoirs in south-eastern Queensland and north-eastern New South Wales.