Imagine finding a living dinosaur in your backyard. That would be a shocking and exciting discovery, right? Well, something similar happened in the world of fish, when some species that were thought to have gone extinct millions of years ago were found alive and swimming in the oceans. In this blog post, we will explore some of these amazing fish and learn more about their history and biology.
Coelacanths: the four-legged fossil fish
Coelacanths are one of the most famous examples of living fossils, which are organisms that have survived unchanged for a very long time. Coelacanths belong to a group of fish that evolved about 400 million years ago and were thought to have died out 65 million years ago, along with the dinosaurs. However, in 1938, a South African museum curator named Marjorie Courtenay-Latimer found a strange blue fish among the catch of a local fisherman. She contacted a fish expert named JLB Smith, who identified it as a coelacanth, a fish that had not been seen alive for millions of years1.
Coelacanths are remarkable for their primitive features, such as their lobed fins that resemble legs and can move in an alternating pattern, like a trotting horse. They also have a hinged joint in their skull that allows them to open their mouth wide, a backbone made of cartilage instead of bone, and an organ that can detect electric fields. Coelacanths can grow up to 2 meters long and weigh up to 100 kilograms. They live in deep waters off the coast of Africa and Indonesia and feed on fish and squid.
Sturgeons: the ancient armoured giants
Sturgeons are another group of fish that have a long evolutionary history and have changed little over time. Sturgeons date back to about 200 million years ago and are characterized by their bony plates or scutes that cover their body, their long snout with sensory barbels, and their heterocercal tail (which means that the upper lobe is longer than the lower one). Sturgeons can reach impressive sizes, with some species growing up to 8 meters long and weighing up to 2 tons. They live in freshwater and marine habitats in Europe, Asia, and North America and feed on worms, crustaceans, and small fish.
Sturgeons are valued for their eggs or roe, which are harvested to make caviar, a delicacy that can fetch high prices. However, this has also led to the decline of many sturgeon populations due to overfishing, poaching, habitat loss, and pollution. Some sturgeon species are critically endangered and face the risk of extinction. For example, the Chinese paddlefish, which was one of the largest freshwater fish in the world, was declared extinct in 2020 after not being seen alive since 20032.
Lungfish: the air-breathing survivors
Lungfish are another ancient group of fish that have some unique adaptations that allow them to survive in harsh environments. Lungfish evolved about 400 million years ago and are named for their ability to breathe air using lungs in addition to gills. This helps them cope with low oxygen levels or drought conditions in their habitats. Lungfish also have lobed fins that can be used for crawling on land or digging burrows where they can aestivate (which means to enter a dormant state) during dry seasons.
Lungfish are found in Africa, South America, and Australia and vary in size and appearance depending on the species. The African lungfish can grow up to 2 meters long and has an eel-like body with scales. The South American lungfish can grow up to 1.5 meters long and has a cylindrical body with smooth skin. The Australian lungfish can grow up to 1.8 meters long and has a stout body with large scales. Lungfish feed on plants, insects, mollusks, crustaceans, and fish.
These are just some examples of fish that were thought to be extinct, but were actually found in living populations. These fish are fascinating for their ancient origins, their unusual features, and their ability to survive in changing environments. They also remind us of the diversity and resilience of life on Earth and the importance of protecting it from extinction.