Protopterus annectens can grow to about 1 metre in total length as an adult, but fossil relatives may have reached 5 metres.
The lifespan of the African lungfish in the wild is unknown, but captive individuals can live for over 100 years!
Protopterus spends most of its time sitting on the river or lake bed and is generally a very inactive animal with a much slower metabolism than a typical fish.
Lungfish kept in captivity are often mistakenly thought to be dead. However, when threatened they can move very quickly.
Protopterus can only breathe air and thus, unusually for a fish, is able to die by drowning.
It breathes through its mouth, and its gills are notably reduced compared to other fish.
Protopterus can go for several minutes between breaths, but it is during these trips to the surface that they are most likely to be seen in the wild.
Protopterus is also able to aestivate - a trick it performs in the dry season when lakes and rivers evaporate and recede. Whilst the muddy bed is still wet, the fish burrows downwards and makes a bulb-shaped chamber that it occupies by curling up. As the mud dries it contracts ensuring enough ventilation for breathing.
Protopterus continually secretes a slimy mucus that dries up during aestivation to form a dehydration-protecting crust.
To survive aestivation Protopterus converts muscle tissue to energy.
Aestivation ends when the wet season returns a few months later.
Protopterus have extremely large cells, perhaps the largest of all animals. This is likely related to their slow metabolism, and potentially important in their ability to aestivate.
The African lungfish has a very large genome, amongst the largest of all animals.
Breeding is triggered by the wet season and hence usually coincides with emergence from aestivation.
Lungfish will protect their young by building underwater nests. These have multiple openings, both underwater and above water - to allow breathing.