Queensland Lungfish
Encyclopedia
The Queensland lungfish, Neoceratodus forsteri (also known as the Australian lungfish, Burnett salmon, and barramunda) is the sole surviving member of the family Ceratodontidae and order Ceratodontiformes. It is one of only six extant lungfish
species in the world. Endemic to Australia
, the Ceratodontidae is an ancient family belonging to the subclass Sarcopterygii
, or fleshy-finned fishes.
Fossil records of this group date back 380 million years, around the time when the higher vertebrate classes were beginning to evolve. Fossils of lungfish almost identical to this species have been uncovered in northern New South Wales
, indicating that Neoceratodus has remained virtually unchanged for well over 100 million years, making it a living fossil
and one of the oldest living vertebrate genera on the planet.
It is one of six extant representatives of the ancient air-breathing Dipnoi (lungfishes) that flourished during the Devonian
period (c. 413-365 million years ago) and is the most primitive surviving member of this lineage.
The five other freshwater lungfish species, four
in Africa and one
in South America, are very different morphologically to N. forsteri. The Queensland lungfish can live for several days out of the water, if it is kept moist, but will not survive total water depletion, unlike its African counterparts.
Fossils almost identical to Neoceratodus forsteri have been uncovered in northern New South Wales, indicating that it has remained virtually unchanged for well over 100 million years.
The small settlement of Ceratodus, Queensland
derives its name from that of the Queensland lungfish.
and Burnett
river systems in south-eastern Queensland
. It has been successfully distributed to other more southerly rivers including the Brisbane
, Albert
, Stanley
, and Coomera River
s, and the Enoggera Reservoir
in the past century. The Queensland lungfish has also been introduced to the Pine
, Caboolture
, and Condamine River
s, but current survival and breeding success are unknown. Formerly widespread, at one time there were at least seven different species of lungfish in Australia.
s, or in underwater caves formed by the removal of substrate under tree roots on river banks. The lungfish is tolerant of cold, but prefers waters with temperatures between 15-25 °C.
The Queensland lungfish is incapable of surviving complete desiccation of its habitat, although it can live out of water for several days if the surface of the skin is constantly moist. Unlike the African species, Protopterus
, it does not survive dry seasons by secreting a mucous cocoon and burying itself in the mud.
The Queensland lungfish is essentially a sedentary species, spending its life within a restricted area. Its home range rarely extends beyond a single pool or, occasionally, two adjacent pools. It does not follow a set migratory path, but may actively seek out suitable spawning habitats between July and December.
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 incisor
s, 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.
Unlike the South-American and African lungfishes, the Australian species has gills on all the first four gill arches, while the fifth arch bears a hemibranch. It's also the only lungfish species that is a facultative air breather, only breathing air when there is not enough oxygen in the water to meet their needs. The lung is a single long sac situated above and extending the length of the body cavity, and is formed by a ventral outgrowth of the gut. Internally, the lung is divided into two distinct lobes that interconnect along its length, compartmentalized by the infolding of the walls.
Each compartment is further divided to form a spongy alveolar region. Blood capillaries run through this region close enough to the air space in the lung to enable gas exchange. Lungfish breathe in using a buccal force-pump similar to that of amphibians. The contraction of smooth muscle
s in the walls of the lung results in exhalation.
The sound of the lungfish exhaling air at the surface prior to inhaling a fresh breath has been compared to that made by a small bellows
. Young lungfish come to the surface to breathe air when they are about 25 mm long.
Eggs are most abundant during September and October. The stimulus for spawning is believed to be day length. The lungfish is known to spawn both during the day and at night. The lungfish is selective in its choice of spawning sites. Eggs have been recorded on aquatic plants rooted in gravel and sand, slow and fast-moving waters, in shade and in full sun, but never on aquatic plants covered with slimy algae, in stagnant water, or where there was loose debris on the water’s surface.
Opposite of its South-American and African relatives, the Australian lungfish does not make a nest and there is no guarding or parental care once it lays its eggs. When spawning does take place, the pair of fish will lie on their sides or become entwined. They usually deposit their eggs singly, occasionally in pairs, but very rarely in clusters. The male lungfish fertilizes each egg as it emerges, and the eggs are deposited in dense aquatic vegetation. The newly laid egg is hemispherical in shape, delicate, heavily yolked, and enclosed in a single vitelline and triple jelly envelope. The egg itself is approximately 3 mm in diameter; with the jelly envelope it has a total diameter of about 1 centimetre (0.393700787401575 in). The egg is sticky for a short while until silt and small aquatic organisms have covered it, but long enough for it to become attached to submerged vegetation. It is negatively buoyant and if it falls to the lake or river bed it is unlikely to survive to hatching.
The female has a large ovary and the potential to lay many eggs, but in the wild only produces a few hundreds of eggs, at most, during her lifetime. In captivity, anywhere from 200 to 500-600 eggs have been laid in a single event. The lungfish does not necessarily spawn every year. A good spawning season occurs approximately once every five years, regardless of environmental conditions.
The eggs and young are similar to those of frogs., but the offspring differ from both frogs and other lungfishes by the absence of external gills during early development. Within the egg, head structures and pigmentation start to appear by day 17. They hatch after 3–4 weeks and resemble tadpole
s. The young fish are slow growing reportedly reaching 27 millimetres (1.1 in) after 110 days, about 60 millimetres (2.4 in)after 8 months. During the first week it lies on its side, hiding in the weeds and moving only when stimulated by touch. It will swim spontaneously, and often retreat back into the gelatinous envelope when disturbed. Newly hatched larvae develop a ciliary current over the skin and gill surfaces. This is believed to either provide respiratory exchange across the skin and gills without necessitating any movements of the jaw or brachial apparatus, or to keep the skin of the unprotected larvae free of debris, parasites, and predatory protozoans. Larvae are reported not to feed for 2–3 weeks while the yolk is still present. By the time the yolk is fully utilized, a spiral valve has developed in the intestine and the fish starts to feed. The young can be fast growing, and can grow about 2 inches per month under optimal conditions.
The Queensland lungfish has very complex courtship behavior made up of three distinct phases. The first is the searching phase, when the fish will range over a large area, possibly searching for potential spawning sites. A pair of fish will perform circling movements at the surface of the water close to beds of aquatic plants. They breathe air more frequently and more noisily than normal, possibly reflecting a greater physiological requirement for oxygen. Individual fish have been observed to breathe air at regular intervals of about 20 minutes, with air breathing accompanied by a distinct loud burp made in the air. It has been suggested that the noisy breathing is a form of a mating call. Observations have been made that lungfish seem to do their noisy breathing in concert, even responding to each other, but never in close vicinity of where the eggs are laid.
The next phase involves behavior similar to “follow-the-leader” during which one fish, the male, shows interest in the female and nudges her with his snout. Up to eight individuals may be involved in follow-the-leader behavior. The male lungfish may occasionally take a piece of aquatic plant into its mouth and wave it around. In the third phase, the fish dive together through aquatic vegetation, the male following the female and presumably shedding milt over the eggs.
Adults have a high survival rate and are long-lived (at least 20–25 years). A Queensland Lungfish at the Shedd Aquarium in Chicago, named "Granddad", has been there since 1933 and is at least 80 years old.
The Queensland lungfish has an unusually large karyotype
, very large chromosome
s and cells, and a high nuclear DNA relative to other vertebrates, but less than what is reported for other lungfishes. In spite of this, it displays low genetic diversity between populations from the Mary, Burnett, and Brisbane catchments. This low level of genetic variation could be attributed to population “bottlenecks” associated with periods of range contraction, probably during the Pleistocene
, and in recent times during the periods of episodic or prolonged drought that are known to reduce some reaches of these river systems.
Lungfish larvae are bottom feeders. They eat micro crustaceans and small Tubifex
worms, occasionally supplementing their diet with filamentous algae
. Soft foods such as worms and plants are partially crushed with a few quick bites and then swallowed. In the adult lungfish, movement of the prey in and out of the mouth is accompanied by strong adduction of the jaws. This crushing mechanism is coupled with hydraulic transport of the food, achieved by movements of the hyoid apparatus, to position the prey within the oral cavity. The Queensland lungfish exhibits the most primitive version of these biomechanical feeding adaptations and behaviors.
Fish and Oyster Act of 1914 and capture in the wild is strictly prohibited. It was placed on the CITES list in 1977. The lungfish is currently protected from fishing and collection for education or research purposes requires a permit in Queensland, under the Fisheries Act of 1994, and from the Commonwealth Government
. It is included on the list of “vulnerable” species, as studies have failed to show that it meets the criteria needed to be considered a threatened or endangered species.
Human activities currently threaten the Queensland lungfish, particularly water development. It is potentially at risk in much of its core distribution in the Burnett and Mary Rivers as 26% of these river systems are presently impounded by weirs and dams. Barriers to movement and altered flow regimes downstream of dams for irrigation purposes could lead to the disruption of existing population structure and cause even more loss of genetic variation.
Queensland lungfish can be very fast growing, yet with a delayed first breeding age. For a long-lived species with naturally low mortality rates, successful spawning and juvenile recruitment is not essential every year and may only occur irregularly in medium to long cycles, even in natural environments. The length of these cycles could easily mask the potentially deleterious impacts on recruitment for many years. Additionally, large adults could remain common for decades and give no indication of a declining population in the longer term.
The Mozambique mouth brooder, or tilapia
, has been declared a noxious and threatening alien species to the lungfish in Queensland.
Lungfish
Lungfish are freshwater fish belonging to the Subclass Dipnoi. Lungfish are best known for retaining characteristics primitive within the Osteichthyes, including the ability to breathe air, and structures primitive within Sarcopterygii, including the presence of lobed fins with a well-developed...
species in the world. Endemic to Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, the Ceratodontidae is an ancient family belonging to the subclass Sarcopterygii
Sarcopterygii
The Sarcopterygii or lobe-finned fishes – sometimes considered synonymous with Crossopterygii constitute a clade of the bony fishes, though a strict classification would include the terrestrial vertebrates...
, or fleshy-finned fishes.
Fossil records of this group date back 380 million years, around the time when the higher vertebrate classes were beginning to evolve. Fossils of lungfish almost identical to this species have been uncovered in northern New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, indicating that Neoceratodus has remained virtually unchanged for well over 100 million years, making it a living fossil
Living fossil
Living fossil is an informal term for any living species which appears similar to a species otherwise only known from fossils and which has no close living relatives, or a group of organisms which have long fossil records...
and one of the oldest living vertebrate genera on the planet.
It is one of six extant representatives of the ancient air-breathing Dipnoi (lungfishes) that flourished during the Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
period (c. 413-365 million years ago) and is the most primitive surviving member of this lineage.
The five other freshwater lungfish species, four
Protopterus
The African lungfishes are the genus Protopterus and constitute the four species of lungfish found in Africa. Protopterus is the sole genus in the family Protopteridae.-Description:...
in Africa and one
South American lungfish
The South American lungfish, Lepidosiren paradoxa, is the single species of lungfish found in swamps and slow-moving waters of the Amazon, Paraguay, and lower Paraná River basins in South America. Notable as an obligate air-breather, it is the sole member of its family Lepidosirenidae...
in South America, are very different morphologically to N. forsteri. The Queensland lungfish can live for several days out of the water, if it is kept moist, but will not survive total water depletion, unlike its African counterparts.
Fossils almost identical to Neoceratodus forsteri have been uncovered in northern New South Wales, indicating that it has remained virtually unchanged for well over 100 million years.
The small settlement of Ceratodus, Queensland
Ceratodus, Queensland
Ceratodus is a settlement in Queensland, Australia on the Burnett River about from Eidsvold, Queensland.-History:The name Ceratodus was given to the settlement about 1922 and derives from that of the Queensland lungfish, neoceratodus forsteri. A railway station opened here 26 April 1924...
derives its name from that of the Queensland lungfish.
Range and distribution
The Queensland lungfish is native only to the MaryMary River (Queensland)
The Mary River is a river system in South East Queensland, Australia. The river rises at Booroobin in the Sunshine Coast hinterland, west of Landsborough...
and Burnett
Burnett River
The Burnett River is a river in central Queensland, Australia that empties into the Pacific Ocean near the city of Bundaberg. The Burnett River region is largely given over to growing sugar cane....
river systems in south-eastern Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
. It has been successfully distributed to other more southerly rivers including the Brisbane
Brisbane River
The Brisbane River is the longest river in south east Queensland, Australia, and flows through the city of Brisbane, before emptying into Moreton Bay. John Oxley was the first European to explore the river who named it after the Governor of New South Wales, Thomas Brisbane in 1823...
, Albert
Albert River (Queensland)
The Albert River is a river in South East Queensland, Australia. Its catchment lies within the Gold Coast and Beaudesert shires and covers an area of 782 square kilometres. The river provides drinking water for the town of Beaudesert....
, Stanley
Stanley River (Queensland)
The Stanley River in Queensland is the main tributary of the Brisbane River. The Stanley River valley extends roughly 35 km westwards from the area south of Maleny to Kilcoy before veering southwards....
, and Coomera River
Coomera River
The Coomera River is a river situated in South East Queensland. The upper reaches of the river flow from the Lamington plateau and the Lamington National Park. Here are the spectacular Coomera Falls in the Coomera Gorge...
s, and the Enoggera Reservoir
Enoggera Reservoir, Queensland
Enoggera Reservoir is an outer suburb of Brisbane, Australia located north-west of the CBD and bordering the Moreton Bay Region and The Gap. It contains Peewee Bend....
in the past century. The Queensland lungfish has also been introduced to the Pine
Pine River (Queensland)
Pine River continues after the convergence of North Pine and South Pine rivers at Lawnton in Queensland, Australia, continuing into Bramble Bay. The Brisway map reference is 440 D10.-Geographical characteristics:...
, Caboolture
Caboolture River
The Caboolture River is a small river in South East Queensland. It rises in the D'Aguilar Range near Ocean View and flows through Caboolture and Morayfield before entering Deception Bay at Beachmere....
, and Condamine River
Condamine River
The Condamine River, part of the Murray-Darling Basin, drains the northern portion of the Darling Downs, an area of sub-coastal southern Queensland, Australia...
s, but current survival and breeding success are unknown. Formerly widespread, at one time there were at least seven different species of lungfish in Australia.
Habitat
This species lives in slow-flowing rivers and still water (including reservoirs) that have some aquatic vegetation present on banks. It occurs over mud, sand, or gravel bottoms. Australian lungfish are commonly found in deep pools of depths between 3–10 meters and live in small groups under submerged logs, in dense banks of aquatic macrophyteMacrophyte
A macrophyte is an aquatic plant that grows in or near water and is either emergent, submergent, or floating. In lakes macrophytes provide cover for fish and substrate for aquatic invertebrates, produce oxygen, and act as food for some fish and wildlife....
s, or in underwater caves formed by the removal of substrate under tree roots on river banks. The lungfish is tolerant of cold, but prefers waters with temperatures between 15-25 °C.
The Queensland lungfish is incapable of surviving complete desiccation of its habitat, although it can live out of water for several days if the surface of the skin is constantly moist. Unlike the African species, Protopterus
Protopterus
The African lungfishes are the genus Protopterus and constitute the four species of lungfish found in Africa. Protopterus is the sole genus in the family Protopteridae.-Description:...
, it does not survive dry seasons by secreting a mucous cocoon and burying itself in the mud.
The Queensland lungfish is essentially a sedentary species, spending its life within a restricted area. Its home range rarely extends beyond a single pool or, occasionally, two adjacent pools. It does not follow a set migratory path, but may actively seek out suitable spawning habitats between July and December.
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 (94.8 lb). It is commonly found to be about 100 centimetres (3.3 ft) and 20 kilograms (44.1 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
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
. 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
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
commences in the middle of the back and is confluent with the caudal and anal fins.
The dentition of the lungfish is unusual: two incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s, 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
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
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.
Breathing
A distinctive characteristic of the Queensland lungfish is the presence of a singel dorsal lung, used to supplement the oxygen supply through the gills. During times of excessive activity, times of drought or high temperatures (when water becomes deoxygenated), or when prevailing conditions inhibit normal functioning of the gills, the lungfish can rise to the surface and swallow air into its lung. It has been shown that more frequent air breathing is correlated with periods of greater activity at night when it uses the lung as a supplementary organ of respiration.Unlike the South-American and African lungfishes, the Australian species has gills on all the first four gill arches, while the fifth arch bears a hemibranch. It's also the only lungfish species that is a facultative air breather, only breathing air when there is not enough oxygen in the water to meet their needs. The lung is a single long sac situated above and extending the length of the body cavity, and is formed by a ventral outgrowth of the gut. Internally, the lung is divided into two distinct lobes that interconnect along its length, compartmentalized by the infolding of the walls.
Each compartment is further divided to form a spongy alveolar region. Blood capillaries run through this region close enough to the air space in the lung to enable gas exchange. Lungfish breathe in using a buccal force-pump similar to that of amphibians. The contraction of smooth muscle
Smooth muscle
Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...
s in the walls of the lung results in exhalation.
The sound of the lungfish exhaling air at the surface prior to inhaling a fresh breath has been compared to that made by a small bellows
Bellows
A bellows is a device for delivering pressurized air in a controlled quantity to a controlled location.Basically, a bellows is a deformable container which has an outlet nozzle. When the volume of the bellows is decreased, the air escapes through the outlet...
. Young lungfish come to the surface to breathe air when they are about 25 mm long.
Reproduction and development
The Queensland lungfish spawns and completes its entire life cycle in freshwater systems. The age of first breeding is estimated to be 17 years for males and 22 years for females. Males typically become mature at 738–790 mm and females at 814–854 mm. After an elaborate courtship, the lungfish spawn in pairs, depositing large adhesive eggs amongst aquatic plants. They spawn from August until November, before the spring rains, in flowing streams that are at least a meter deep.Eggs are most abundant during September and October. The stimulus for spawning is believed to be day length. The lungfish is known to spawn both during the day and at night. The lungfish is selective in its choice of spawning sites. Eggs have been recorded on aquatic plants rooted in gravel and sand, slow and fast-moving waters, in shade and in full sun, but never on aquatic plants covered with slimy algae, in stagnant water, or where there was loose debris on the water’s surface.
Opposite of its South-American and African relatives, the Australian lungfish does not make a nest and there is no guarding or parental care once it lays its eggs. When spawning does take place, the pair of fish will lie on their sides or become entwined. They usually deposit their eggs singly, occasionally in pairs, but very rarely in clusters. The male lungfish fertilizes each egg as it emerges, and the eggs are deposited in dense aquatic vegetation. The newly laid egg is hemispherical in shape, delicate, heavily yolked, and enclosed in a single vitelline and triple jelly envelope. The egg itself is approximately 3 mm in diameter; with the jelly envelope it has a total diameter of about 1 centimetre (0.393700787401575 in). The egg is sticky for a short while until silt and small aquatic organisms have covered it, but long enough for it to become attached to submerged vegetation. It is negatively buoyant and if it falls to the lake or river bed it is unlikely to survive to hatching.
The female has a large ovary and the potential to lay many eggs, but in the wild only produces a few hundreds of eggs, at most, during her lifetime. In captivity, anywhere from 200 to 500-600 eggs have been laid in a single event. The lungfish does not necessarily spawn every year. A good spawning season occurs approximately once every five years, regardless of environmental conditions.
The eggs and young are similar to those of frogs., but the offspring differ from both frogs and other lungfishes by the absence of external gills during early development. Within the egg, head structures and pigmentation start to appear by day 17. They hatch after 3–4 weeks and resemble tadpole
Tadpole
A tadpole or polliwog is the wholly aquatic larval stage in the life cycle of an amphibian, particularly that of a frog or toad.- Appellation :...
s. The young fish are slow growing reportedly reaching 27 millimetres (1.1 in) after 110 days, about 60 millimetres (2.4 in)after 8 months. During the first week it lies on its side, hiding in the weeds and moving only when stimulated by touch. It will swim spontaneously, and often retreat back into the gelatinous envelope when disturbed. Newly hatched larvae develop a ciliary current over the skin and gill surfaces. This is believed to either provide respiratory exchange across the skin and gills without necessitating any movements of the jaw or brachial apparatus, or to keep the skin of the unprotected larvae free of debris, parasites, and predatory protozoans. Larvae are reported not to feed for 2–3 weeks while the yolk is still present. By the time the yolk is fully utilized, a spiral valve has developed in the intestine and the fish starts to feed. The young can be fast growing, and can grow about 2 inches per month under optimal conditions.
The Queensland lungfish has very complex courtship behavior made up of three distinct phases. The first is the searching phase, when the fish will range over a large area, possibly searching for potential spawning sites. A pair of fish will perform circling movements at the surface of the water close to beds of aquatic plants. They breathe air more frequently and more noisily than normal, possibly reflecting a greater physiological requirement for oxygen. Individual fish have been observed to breathe air at regular intervals of about 20 minutes, with air breathing accompanied by a distinct loud burp made in the air. It has been suggested that the noisy breathing is a form of a mating call. Observations have been made that lungfish seem to do their noisy breathing in concert, even responding to each other, but never in close vicinity of where the eggs are laid.
The next phase involves behavior similar to “follow-the-leader” during which one fish, the male, shows interest in the female and nudges her with his snout. Up to eight individuals may be involved in follow-the-leader behavior. The male lungfish may occasionally take a piece of aquatic plant into its mouth and wave it around. In the third phase, the fish dive together through aquatic vegetation, the male following the female and presumably shedding milt over the eggs.
Adults have a high survival rate and are long-lived (at least 20–25 years). A Queensland Lungfish at the Shedd Aquarium in Chicago, named "Granddad", has been there since 1933 and is at least 80 years old.
The Queensland lungfish has an unusually large karyotype
Karyotype
A karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...
, very large chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
s and cells, and a high nuclear DNA relative to other vertebrates, but less than what is reported for other lungfishes. In spite of this, it displays low genetic diversity between populations from the Mary, Burnett, and Brisbane catchments. This low level of genetic variation could be attributed to population “bottlenecks” associated with periods of range contraction, probably during the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
, and in recent times during the periods of episodic or prolonged drought that are known to reduce some reaches of these river systems.
Diet and feeding habits
The Queensland lungfish is primarily nocturnal, and is essentially carnivorous. In captivity it will feed on frogs, earthworms, pieces of meat, and pelleted food. In the wild its prey includes frogs, tadpoles, fishes, a variety of invertebrates, and plant material. No quantitative dietary data is available, but anecdotal observations clearly indicate that the diet of the lungfish changes with development. This is proven to be correlated with a change in dentition.Lungfish larvae are bottom feeders. They eat micro crustaceans and small Tubifex
Tubifex
Tubifex is a cosmopolitan genus of tubificid Annelids that inhabit the sediments of lakes, rivers and occasionally sewer lines. There are over ten known species of Tubifex, but the number is not certain, as the species are not easily distinguishable from each other.-Food and feeding:Tubifex worms...
worms, occasionally supplementing their diet with filamentous algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
. Soft foods such as worms and plants are partially crushed with a few quick bites and then swallowed. In the adult lungfish, movement of the prey in and out of the mouth is accompanied by strong adduction of the jaws. This crushing mechanism is coupled with hydraulic transport of the food, achieved by movements of the hyoid apparatus, to position the prey within the oral cavity. The Queensland lungfish exhibits the most primitive version of these biomechanical feeding adaptations and behaviors.
Conservation status
Although the status of the Queensland lungfish is secure, it is a protected species under the QueenslandQueensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
Fish and Oyster Act of 1914 and capture in the wild is strictly prohibited. It was placed on the CITES list in 1977. The lungfish is currently protected from fishing and collection for education or research purposes requires a permit in Queensland, under the Fisheries Act of 1994, and from the Commonwealth Government
Government of Australia
The Commonwealth of Australia is a federal constitutional monarchy under a parliamentary democracy. The Commonwealth of Australia was formed in 1901 as a result of an agreement among six self-governing British colonies, which became the six states...
. It is included on the list of “vulnerable” species, as studies have failed to show that it meets the criteria needed to be considered a threatened or endangered species.
Human activities currently threaten the Queensland lungfish, particularly water development. It is potentially at risk in much of its core distribution in the Burnett and Mary Rivers as 26% of these river systems are presently impounded by weirs and dams. Barriers to movement and altered flow regimes downstream of dams for irrigation purposes could lead to the disruption of existing population structure and cause even more loss of genetic variation.
Queensland lungfish can be very fast growing, yet with a delayed first breeding age. For a long-lived species with naturally low mortality rates, successful spawning and juvenile recruitment is not essential every year and may only occur irregularly in medium to long cycles, even in natural environments. The length of these cycles could easily mask the potentially deleterious impacts on recruitment for many years. Additionally, large adults could remain common for decades and give no indication of a declining population in the longer term.
The Mozambique mouth brooder, or tilapia
Tilapia
Tilapia , is the common name for nearly a hundred species of cichlid fish from the tilapiine cichlid tribe. Tilapia inhabit a variety of fresh water habitats, including shallow streams, ponds, rivers and lakes. Historically, they have been of major importance in artisan fishing in Africa and the...
, has been declared a noxious and threatening alien species to the lungfish in Queensland.