Neoceratodus forsteri

Geographic Range

Australian lungfish are found in south-eastern Queensland in Australia, in the Burnett, Mary, North Pine, and Brisbane Rivers, as well as in the Enoggera Reservoir. Their exact native distribution, however, cannot be verified due to the transplantation of several lungfish in 1898 to the Enoggera Reservoir, the North Pine River, the Brisbane River, and various other locations where they were previously believed not to exist (Kemp 1987). Many of these translocated populations may now be low in abundance if not completely absent from some areas. Australian lungfish are partially restricted to their current environment, because they cannot survive in saline water. This inhibits migration through seas to other potentially habitable locations. Also, the splitting of Pangaea is believed to have geographically isolated Australian lungfish (Alrubaian et al 2006).

• Biogeographic Regions
• australian australian
  • native native

Habitat

Typical habitats of Australian lungfish consist of “still or slow-flowing, shallow, vegetated pools” in areas of constant, lasting water (Department of the Environment et al. 2009). Ideal environments are shaded and away from open water and are characterized by permanent water, little mud, and vegetation and a substrate composed of fine sand and gravel. Australian lungfish are found in deep water in winter and during the day and in shallower water in the spawning season and at night. In other areas, mature lungfish dwell in or near dense and overhanging vegetation. Young lungfish inhabit areas adjacent to complex weed banks and remain in such habitats for months or years.

• Habitat Regions
• tropical tropical
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• temporary pools

Physical Description

Mature Australian lungfish possess a “wide flat head, a thick heavy body, a diphycercal tail, and paddle-shaped fins” (Kemp 1987). Lungfish range in size from about 82.5 to 112.5 cm, though some have measured up to 2 m. Large individuals can weigh up to 48 kg. Except for the anterior region of the head, Australian lungfish are enveloped with a network of at least four overlapping scales, which provides some protection for its more pregnable, underlying areas. Adults have a tiny mouth with relatively large teeth on the palate and the lower jaw. They are olive-green or grey-brown in color on the dorsal side, yellow-orange below, and also have some white on their ventral side. In contrast to adults, juvenile lungfish have a more circular head, shorter fins, a scrawny trunk, and their underside is a faint pink color. Males and females appear the same, though the belly color of males changes during the breeding season.

Australian lungfish have a single lung, as opposed to the paired lungs present in the other species of lungfish Lepidosiren paradoxa . This lung is used for aerobic respiration when it is more animated and needs additional oxygen. Increased dependency on oxygen in lungfish takes place only under specific circumstances, such as while grazing for food at night, during periods of flood when waters are highly turbid, and/or throughout spawning.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Development

Length of each stage of development varies considerably among individual Australian lungfish. Egg persistence is highest in shallow water that is condensed with macrophytes. Each egg produced is enveloped in a “vitelline” and a three-layered jelly membrane. Cleavage occurs briskly, and after 36 hours a large-celled blastula forms. After about 3.5 to 4.5 days, the small-celled blastula develops, and invagination occurs after a large fluid-filled blastocoel is produced around 7 days. The “gastrulation stages” take place during the next day in most cases, and neurulae arise during the following 2 days. Four to 6 days later, head structures begin to appear as the head starts to extend forwards. Initial formation of pigment occurs around the 17th day. During this time, the vitelline expands and broadens, yielding various cracks until it is completely broken up and separated. As the embryo further develops, the middle layer of the “triple jelly” lining disintegrates from the inside, slowly inducing the expansion of the outermost layer or “capsule.” Just prior to hatching, lungfish express pigmentation and the lateral line system appears. Also around this stage in development, body proportions and position of mouth and dorsal fin change, and a pre-anal fin grows.

Hatching of Australian lungfish takes place as fish squeeze through a diminutive hole in the side of the capsule, which can occur as early as 23 days depending on environmental conditions. Hatching usually occurs after about 30 days. While the yolk is still available, the hatchling lies decumbently on its side. Feeding starts 4 to 6 weeks after hatching. In time, young Australian lungfish begin to feed more edaciously and act with less fear. They show no obvious external metamorphic activity and no definite distinction between individuals can be made until they become true adults. Most lungfish appear in close proximity to adults for 6 to 7 months after hatching. Adults retain some juvenile characteristics and “larval features”, suggesting that lungfish exhibit some paedomorphosis.

• Development - Life Cycle
• neotenic/paedomorphic

Reproduction

Male Australian lungfish reach sexual maturity at 15 years of age, while females reach sexual maturity at 20 years of age. Lungfish perform an elaborate routine of mating behaviors, but little is known about this process. Loud sounds made by lungfish when breathing air may also be involved in the mating process, though this is uncertain. Australian lungfish have been observed frequently and hastily circling in pairs near the water’s surface during mating season. Australian lungfish lay their eggs lying on their side while they are attached to a partner. Eggs are usually deposited individually, though occasionally in pairs, within waters of 16 to 26 degrees Celsius in temperature. Each female usually lays 50 to 100 eggs per mating, although each is capable of laying many more. About 95% of emerging eggs are immediately fertilized by the male and are carefully directed into a deligated environment. However, in contrast to this recorded act of deliberation, Australian lungfish have also been noted to “thrash their tails at the end of spawning...to disperse the eggs” (Department of the Environment et al. 2009). Eggs can be produced at any time during the day or night. Lungfish eggs best survive at depths of 200 to 800 mm.

Australian lungfish spawn from August to December, but eggs are most plentiful in September and October. Progeneration is initiated in correspondence to the increasing length of days and does not depend on rainfall or the water’s chemical make-up. Australian lungfish choose spawning sites with incredible specificity, though the manner of selection is unknown, as numerous suitable environments exist along riverbanks. Factors such as water depth, substrate composition, prevalence and composition of macrophyte species, and the height of surrounding macrophytes are crucial components of their choice of spawning site. Australian lungfish often choose a macrophyte species with “complex branching or leaf worls...because eggs that detach from the surface of these are less likely to fall to the bottom” (Department of the Environment et al. 2009). Ideal macrophyte beds contain an intricate network of algae, protozoa, worms, small mollusks and crustaceans. In the event that only an inadequate portion of the required spawning conditions can be met, Australian lungfish do not reproduce. Due to the specificity of breeding sites, complete progeneration has exclusively occured about every 20 years for more than a century. During breeding, Australian lungfish act very differently in stagnant water than in moving water. In calm waters, eggs are rarely found deeper than 50 to 100 mm, and lungfish opt to breed in areas where the substrate is sandy. In contrast, within flowing waters, eggs are often laid at depths of 200 to 600 mm in several different substrates.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • external external
• oviparous oviparous

A nest or refuge is not produced by Australian lungfish parents. No protection or help is provided to offspring, as eggs are left on their own to develop after hatching.

• Parental Investment
• no parental involvement

Lifespan/Longevity

Australian lungfish can live 50 to 100 years.

Behavior

When occupying naturally flowing water, Australian lungfish are fairly sedentary. They commonly move around 1 or 2 different pools at night and retreat to a specific part of their habitat each day for rest and recovery. Unlike adults, juvenile Australian lungfish behave territorially and aggressively towards other juveniles. Larger young fish have been observed physically shoving and biting smaller juveniles in order to inhibit their occupation of the more ideal available habitats.

• Key Behaviors
• natatorial natatorial
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• territorial territorial

Home Range

Little information is available regarding the home range of Australian lungfish. Juveniles, however, behave territorially toward other juveniles.

Communication and Perception

Little is known regarding the means of sensory perception and communication of Australian lungfish. Young juveniles can undergo a color change as response to light stimulation, but this capability is slowly inhibited as the presence of pigment increases. Despite the common misbelief that eyes of lungfish are of little to no use, Australian lungfish do exhibit some level of phototaxy due to the presence of opsins, which allow the fish to “fine-tune [their] spectral sensitivity to environmental light” (Bailes et al. 2007). Three different types of cones equip lungfish with the potential to see in color. Some of these cones contain “brightly coloured oil droplets or spectral filters...thought to improve colour vision" (Bailes et al. 2006). These spectral filters also increase the ability of lungfish to distinguish between objects based on their color, “including those of ecological significance” (Bailes et al. 2006). This ability could aid lungfish greatly in the essentially transparent waters of their freshwater habitats. In addition to visual perception, lungfish utilize electroreception to detect faint, electric fields encompassing hidden, potential prey. Australian lungfish are also capable of picking up vibrations produced by other animals, which is useful for hunting and survival.

• Perception Channels
• visual visual
• vibrations vibrations
• electric electric

Food Habits

The diet of Australian lungfish changes with their progressive development, especially as their dentition develops. When young lungfish first begin to feed, they possess several “sharp, cone-shaped teeth” that act to seize and hold their quarry (Department of the Environment et al. 2009). At this stage, they typically cull worms and small crustaceans such as brine shrimp . Young juveniles also may attempt to prey on animals similar in size to themselves, although this is not frequent, as digestion is routinely limited.

Eventually, the cone-shaped teeth of Australian lungfish expand and slightly erode into tooth plates. Adults are “benthic omnivores” (Department of the Environment et al. 2009). These mature fish feed on a variety of animals including “ frogs , tadpoles, fishes, shrimps , prawns , earthworms , aquatic snails, bivalve mollusks ... moss , fallen flowers from Eucalyptus trees and aquatic plants” (Department of the Environment et al. 2009). Outside of their natural environment, adults have been observed consuming several additional foods, such as “insect larvae...meat, offal...dried dog or poultry food...and dead toads” (Kemp 1987). While hunting for food, lungfish often eat some plants, which pass through their body undigested. This vegetation may be ingested in order to also consume miniscule organisms bound to it.

• Primary Diet
• omnivore omnivore

• Animal Foods
• amphibians
• fish
• insects
• mollusks
• terrestrial worms
• aquatic crustaceans

• Plant Foods
• flowers
• bryophytes

Predation

Certain endemic fishes, such as Tilapia , are speculated to feed on juveniles and the eggs of Australian lungfish. They also may compete with adult lungfish for breeding sites. Other predators of pre-mature, young lungfish also include insect larvae, small crustaceans, jewfish , and wood ducks .

Ecosystem Roles

Australian lungfish prey on a variety of organisms, but little else is known about their role in their ecosystem. They may compete with certain endemic fish, like Tilapia , for breeding sites.

Economic Importance for Humans: Positive

Australian lungfish are important to research because of their position as "living fossils." Research on lungfish helps to elucidate the life history of ancestors of all land vertebrates.

• Positive Impacts
• research and education

Economic Importance for Humans: Negative

There are no negative impacts of Australian lungish on humans.

Conservation Status

There are estimated to be fewer than 10,000 Australian lungfish currently in existence. In 2003, the species was declared a “vulnerable species” by the Environmental Protection and Biodiversity Conservation Act. Australian lungfish have been safeguarded by the Aborigines for thousands of years prior to the application of this protective label (Arthington 2008). Habitats of Australian lungfish have been negatively affected by environmental changes associated with agriculture, forestry, invasive species, and river impoundment. These changes to rivers reduce lungfish populations, disrupt the breeding process, and decrease juvenile recruitment. Man-made barriers, such as dams, change water quality downstream, as they frequently release oxygen deprived, sediment rich water that is detrimental to lungfish populations. Dams also limit lungfish movement, preventing the migration of adults to spawning areas. Dam induced flooding also destroys algal macrophyte beds. Macrophyte beds demolished within 6 weeks dam construction may need years to reform the dense beds that previously thrived. These floods also have the potential to kill hundreds of lungfish. Additional environmental threats to Australian lungfish include fertilizer and sewage runoff from agricultural activities, human effluents, and animal production facilities. Australian lungfish populations lack genetic diversity, which may further threaten the long-term survival of the species.

Additional Links

Encyclopedia of Life

Contributors

Stewart Garner (author), University of Alabama, Nancy Shefferly (editor), Animal Diversity Web Staff, Tanya Dewey (editor), University of Michigan-Ann Arbor, Gail McCormick (editor), Animal Diversity Web Staff.

References

Alrubaian, J., J. Lee, R. Dores. 2006. Are lungfish living fossils? Observation on the evolution of the opoid gene/orphnin gene family. General and Comparitive Endocrinology , 148: 304-316.

Arthington, A. 2008. Australian lungfish, Neoceratodus forsteri, threatened by a new dam. Environmental Biology of Fishes , 8: 211-221.

Bailes, H., S. Collin, A. Trezise, W. Davies. 2007. Visual pigments in a living fossil, the Australian lungfish Neoceratodus forsteri. BMC Evolutionary Biology , 7: 1-8.

Bailes, H., S. Robinson, A. Trezise, S. Collin. 2006. Morphology, characterization, and distribution of retinal photoreceptors in the Australian lungfish Neoceratodus forsteri. Journal of Comparative Neurology , 494: 381-397.

Daczewska, M., A. Kacperczyk. 2008. The Australian lungfish (Neoceratodus forsteri)-fish or amphibian pattern of muscle development?. International Journal of Developmental Biology , 52: 279-286.

Department of the Environment, Water, Heritage and the Arts, 2009. "Neoceratodus forsteri - Australian lungfish" (On-line). Department of the Environment, Water, Heritage and the Arts. Accessed March 26, 2009 at http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=67620 .

Evans, C., M. Watt, J. Joss. 1999. Use of electrorecption during foraging by the Australian lungfish. Animal Behavior , 58: 1039-1045.

Joss, J. 2009. "A Very Special Fish-Australian Lungfish under Threat" (On-line). Accessed March 26, 2009 at http://www.thepetitionsite.com/1/a-very-special-fish-australian-lungfish-under-threat .

Joss, J. 2005. Lungfish Evolution and Development. General and Comparative Endocrinology , 148: 285-289.

Kemp, A. 1987. The Biology of the Australian Lungfish, Neoceratodus forsteri. Centennial Supplement: Journal of Morphology , 1: 181-198.

Pearson, H. 2006. Dam project threatens living fossil. Nature , 442: 232-233. Accessed March 26, 2009 at http://www.nature.com/nature/journal/v442/n7100/full/442232b.html .