Jellyfish are amazing creatures that have the ability to regenerate body parts after injury or amputation.
This remarkable feat has fascinated scientists for decades, who have been trying to unravel the secrets behind their regenerative powers.
The cellular mechanisms of jellyfish regeneration
OLIVIER MORIN/AFP via Getty Images
One of the jellyfish species that can regenerate its tentacles is Cladonema, which has branching tentacles that it uses to capture prey and defend itself.
When a tentacle is cut off, Cladonema can grow a new one in two to three days.
Researchers from University of Tokyo in Japan have recently revealed the cellular mechanisms that enable Cladonema to regenerate its tentacles.
They found that the process involves three main steps: remodeling, stabilization, and growth.
First, the jellyfish undergoes a remodeling phase, where the cells near the wound site contract and reshape the body umbrella, the bell-shaped part of the jellyfish.
This creates a radial pattern of muscle fibers that converge around hubs, which are clusters of cells that serve as positional landmarks for the new tentacle.
Second, the hubs are stabilized by the expression of a gene called Wnt6, which is involved in many developmental processes in animals.
The expression of Wnt6 depends on the configuration of the muscle fibers that surround the hubs. The hubs then become the source of a signaling molecule called β-catenin, which activates the growth of the new tentacle.
Third, the new tentacle grows from a blastema, which is a mass of undifferentiated cells that can differentiate into various cell types. The blastema is fueled by both cell proliferation and cell migration from distant regions of the body.
The growth of the new tentacle is also influenced by its connection to the gastrovascular canal system, which is the network of tubes that transports nutrients and oxygen throughout the jellyfish body.
Jellyfish belong to the phylum Cnidaria, which is one of the earliest diverging animal groups, dating back to more than 500 million years ago.
Cnidarians have a simple body plan with radial symmetry, meaning that they have no left or right sides, only a top and a bottom.
By studying how jellyfish regenerate their tentacles, we can gain insights into how the basic body plan of animals evolved, and how different types of symmetry emerged.
For example, the radial pattern of muscle fibers and hubs that Cladonema forms during regeneration resembles the body axis of bilaterally symmetrical animals, which have a left and a right side, such as humans.
This suggests that there may be a common origin for the mechanisms that control body patterning in animals, and that radial symmetry may have been a precursor for bilateral symmetry.
Moreover, by comparing the regenerative abilities of different jellyfish species, we can learn how regeneration evolved and diversified in animals.
For instance, another jellyfish species, Clytia, which has unbranched tentacles, can also regenerate its tentacles, but it does so by a different mechanism that involves the formation of a ring of cells around the wound site.
This shows that there are multiple ways to achieve regeneration, and that different jellyfish species have adapted to different environmental and ecological conditions.
Jellyfish regeneration is a fascinating phenomenon that reveals the amazing plasticity and resilience of animal life.
By studying how jellyfish can grow back their tentacles in days, we can not only marvel at their superpowers, but also deepen our knowledge of animal development and evolution.
