The Illustrious Dipnoi

This odd fish has 30 times as much DNA as humans—a new record for animals

Lacking key genes that control selfish bits of DNA, the South American lungfish’s genome just grew and grew.

A species of lungfish found in South America has claimed the title of the animal with the biggest genome sequenced so far. The DNA of Lepidosiren paradoxa comprises a staggering 91 billion chemical letters or “bases,” 30 times as many as the human genome, researchers report today in Nature. However, those 91 billion bases of DNA only contain about the same number of genes that humans have—roughly 20,000—with the rest consisting of noncoding, perhaps even “junk” DNA. By comparing this genome with those of other lungfishes, the researchers determined that L. paradoxa adds the equivalent of a human genome to its DNA every 10 million years...

Australian Lungfish (Neoceratodus forsteri), family Neoceratodontidae, order Ceratodontiformes, class Dipnoi, Australia

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Lungfish are truly wondrous critters

The spotted lungfish, also known as the slender lungfish, or scientific name Protopterus dolloi, is a unique fish, even within the lungfish family! Found in and around Western and North Africa, spread through the Congo river basin. This fish is entirely freshwater, even living exclusively above Stanley pool, a particularly slow section of the river near the mouth of the sea, above which the water has less salt. The spotted lungfish in particular is a demersal species living in and around the river bed, as well as in temporary floodplains created by the Congo. 

Lungfish are known for their impressive lungs made from a modified swim bladder, these fish are obligate air breathers, meaning they possess both gills and lungs. The slender lungfish in particular, as well as all African lungfish, have working gills, however the gills are not sufficient for air intake, so these fish must rise to the surface of the water for air periodically. Lungfish are also known for their adaptations for surviving the dry season, being able to survive a drought for up to 3 years with no water. This is done by creating a cocoon in the mud made out of mucus where the fish will enter aestivation, a kind of voluntary hibernation to slow use of nutrients and creation of wastes. This is unique to lungfish, as most fish when outside of water have waste products wash back into the gills giving them ammonia toxicity, without water to remove these wastes. However, the lungfish can stop waste production protecting them from this. The humble lungfish also possesses fins specifically made for crawling on land, giving them the ability to traverse, albeit slowly, and with significant struggle. 

The spotted lungfish is an opportunistic omnivore. Eating primarily live prey and various meats, these fish only consume algae and various vegetation when necessary. The diet is primarily made up of fish, mollusks, and crustaceans. These fish have surprising agility and speed, easily catching prey by sucking it into their mouth. Even going so far as to spit out food and suck it up repeatedly to get rid of hard shells. Hunting at night and remaining still and camouflaged in the daylight. 

Breeding season for these fish comes from June to October. The spotted lungfish lives in areas of the Congo river which very rarely dries completely, and as such one might assume their ability to burrow and survive in little water would be lost on this species. However, these fish create burrows just like those made in times of drought each year to lay eggs within. Male lungfish will create this burrow and court a female to come inside and lay eggs. The male will then spend the remainder of this season guarding these eggs and then larvae upon hatching. During this the female will spend her time in open waters, to find more male fish. The larvae, once hatched, will spend a few weeks with the father, eating insects and various plant matter before emerging into the river on their own. Throughout their lives, these fish start with gills that are near exclusively what they breathe through, but these will fade as they age forcing them to surface or air more frequently, just as the spots their name comes from will!  These fish are solitary, and are known to attack one another when forced in small spaces, and as such many of these fish will only see another at birth and breeding seasons. Most of these fish will die, with almost all fish passing well before reaching adulthood, those who survive can reach sizes as large as 30 inches, and live up to 20 years before passing. 

That's the fish of the day, everybody! I hope you enjoyed learning about the fish.

Sources:

Protopterus dolloi summary page. (n.d.-a). https://fishbase.se/summary/Protopterus-dolloi

Protopterus dolloi (slender lungfish) — seriously fish. (n.d.-a). https://www.seriouslyfish.com/species/protopterus-dolloi/

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