Fish with the longest genome: A tiny, unassuming evolutionary marvel

Scientists have made a breakthrough in research on fish with an incredibly long genome. Surprisingly, the record holder is neither a giant nor a particularly intellectually advanced creature.

Here's another proof of how amazing the world of aquatic creatures is. The undisputed speed record holder is the Pacific sailfish, while the unassuming Lepidosiren paradoxa is the current record holder in the DNA length category.

A team of scientists, including biologist Axel Meyer from the University of Konstanz in Germany, has sequenced the genome of Lepidosiren paradoxa, a South American fish from the lungfish subclass. Its DNA consists of over 90 billion base pairs, twice as many as the previous record holder.

The discovery, published in Nature, sheds light on fish's evolutionary history and their crucial role in our ancestors' transition from water to land, reports Science Alert.

Lepidosiren paradoxa possesses DNA thirty times longer than that of humans. Surprisingly, scientists "counted" only about 20,000 protein-coding genes, comparable to the human gene pool. 

A significant portion of this fish's DNA consists of so-called "jumping genes," which can copy and move within the genome, possibly contributing to rapid genetic changes in the past. These findings may help us understand how tetrapods evolved and conquered land.

These fish are considered living fossils and have a unique feature — they possess lungs that allow them to breathe atmospheric air. These extraordinary creatures provide valuable insights into the evolution of life on land. Meyer, Schartl, and their international team discovered that the enormous size of their genome might result from low levels of piRNA (a type of RNA that usually suppresses transposon activity). 

Their research confirmed that jumping genes are still active, suggesting that their genome continues to grow. Despite this, the genome has proven exceptionally stable and retains many characteristics of its ancestors.