This fish has a highly evolved respiratory system, taking oxygen directly from the air like terrestrial animals.
While most fish need water to survive, there’s a unique creature that has evolved remarkably: it can live underground for years without water or food. This is the African lungfish (Protopterus).
Appearing approximately 390 million years ago, lungfish are called “living fossils” by scientists because they retain many primitive characteristics. This fish primarily inhabits the Bandama River basin in Côte d’Ivoire and African swamps, areas frequently hit by severe droughts.
These fish range in size from 44-200 cm when mature. They have an elongated body, somewhat resembling an eel in appearance. Their pectoral and pelvic fins are thread-like, while the dorsal and caudal fins are fused into a single structure. Their entire body is covered in soft scales. They swim with an undulating motion like an eel or crawl along the bottom using their pectoral fins.
Due to the year-round high temperatures in Africa and the extremely harsh dry season, which often lasts at least 4-5 months and causes rivers and lakes to dry up, lungfish have developed a truly unique respiratory system, possessing both gills and two lungs, to survive.
The lungfish has a highly evolved respiratory system, capable of taking oxygen directly from the air like terrestrial animals. Because the oxygen levels in the water are insufficient to sustain life, they frequently surface to breathe air—a rare behavior for fish.
When in water, they move and feed like other fish. However, during the dry season, they dig deep burrows in the soft mud by ingesting mud through their mouths and expelling it through their gills. Once they reach the desired depth, they stop digging and secrete mucus from their mouths to harden the mud, creating a protective cocoon, with only their mouth exposed for air.
If the drought persists, African lungfish enter a state of aestivation, similar to hibernation in some cold-region animals. Amazingly, lungfish can maintain this state for up to 4-5 years, without needing water or food.
Recent genetic and biological studies have documented profound changes in the lungfish’s body when it begins its long sleep:
Sharply reduced metabolism: Oxygen consumption decreases by over 50%, and heart rate drops from 25 beats per minute to about 2 beats per minute.
Cessation of ammonia production: This reduces excretory pressure, preventing the accumulation of toxins in water-deprived conditions.
Shrinking of internal organs: The intestines, kidneys, and heart all decrease in size and activity, maximizing energy conservation.
Changes in gene and hormone activity: Genes related to metabolism are suppressed, while genes involved in antioxidant activity and cell repair are activated.
All these changes help the lungfish enter a “semi-alive” state—a temporary pause that still maintains potential life for many years.
Four species of African lungfish are recognized: the Marbled African lungfish (Protopterus aethiopicus), the East African lungfish (Protopterus amphibius), the West African lungfish (Protopterus annectens), and the Spotted African lungfish (Protopterus dolloi). There are some differences in their appearance and behavior.
Since ancient times, indigenous African people have caught lungfish by digging in the ground or setting nets for food. Their flesh has a strong flavor and is not widely preferred, yet lungfish remain a valuable food source in the harsh living conditions of the region.
Today, the West African lungfish is bred in aquaculture farms and sold on the international market as a unique aquarium fish. In the wild, their numbers are declining due to uncontrolled fishing.