Fish and Salamanders Reveal Secrets to Regrowing Limbs

The ability to regenerate lost limbs, a staple of science fiction, may not be as far-fetched as once believed. While humans currently lack this remarkable capacity, new research published on January 22, 2026 in Nature Communications has revealed shared genetic and cellular mechanisms underlying appendage regeneration in fish and salamanders, offering clues about the evolutionary history of this trait and potentially informing future regenerative medicine efforts.

The study, led by Igor Schneider, an evolutionary developmental biologist at Louisiana State University, focused on the Senegal bichir (Polypterus senegalus), an ancient fish capable of fully regenerating its fins. This species is considered a “living fossil” due to its evolutionary position, providing a window into the early development of regenerative abilities in vertebrates. Researchers compared the bichir’s regenerative process to that of the axolotl, a salamander renowned for limb regrowth, and the zebrafish, which can regenerate the tips of its fins.

The research team tracked gene activity at the wound site following amputation in all three species, observing a surprisingly consistent initial response. In all cases, immune cells rapidly migrated to the injury, first working to combat bacteria – a common reaction even in human wound healing. However, a crucial difference emerged in the bichir and axolotl. Their immune systems quickly modulated the inflammatory response, preventing the formation of scar tissue, a critical step for successful regeneration. Scar tissue formation typically hinders regeneration, and its absence appears vital in these species.

Injuries often disrupt blood supply and oxygen flow, complicating healing. The study revealed that these three animals compensated for this disruption by activating metabolic pathways that allowed cells to produce energy without relying on oxygen. The researchers observed an unexpected increase in myoglobin, a protein typically found in muscle tissue for oxygen storage, appearing in skin cells covering the wounds. Even more striking was the influx of red blood cells to the amputation site in both the bichir and axolotl, increasing their concentration at the wound to as much as 20 percent – a significant jump from the typical 2 percent found in healthy tissue.

Interestingly, the red blood cells in both the bichir and axolotl retain their nuclei, unlike mature human red blood cells. Within these nuclei, the team found increased activity of genes controlling immune responses and monitoring oxygen levels. Schneider suggests that these nucleated red blood cells may be “giving instructive signals” to other cells, actively participating in the regenerative process rather than simply providing oxygen.

The study also identified the activation of genes involved in limb building and DNA repair, with two distinct groups of repair cells forming – one near the base of the regenerating limb and another near the tip. This coordinated activity highlights the complexity of the regeneration process.

According to Ji-Feng Fei, a developmental biologist at the Guangdong Academy of Medical Sciences in Guangzhou, China, who was not involved in the study, the work “is a big step in understanding how regeneration is coordinated.” The shared aspects of regeneration observed across these distantly related species – which diverged approximately 400 million years ago – suggest that the ability to regenerate is an ancient trait, potentially present in early vertebrates.

Researchers are now looking to expand these studies to other species, such as lizards, which can regenerate their tails but not their limbs. Understanding why some animals can regenerate certain body parts but not others could provide further insights into the underlying mechanisms. Schneider wryly notes that, in the context of fictional limb regeneration, “Spider-Man’s foil might have been more successful with salamander DNA, unless he wanted to regrow a tail.”

While the prospect of human limb regeneration remains a distant goal, this research provides a crucial foundation for future investigations. The identification of shared genetic and cellular pathways offers potential targets for therapeutic interventions aimed at stimulating regenerative processes in humans, potentially leading to new treatments for injuries and conditions that currently result in permanent tissue loss.