Alien-like comb jellies raise questions on the evolution of nervous systems

The nervous system of most animals, including humans, relies on synapses. Synapses are the gaps between nerve cells that enable communication through the release of neurotransmitters. 

However, comb jellies have a completely different approach. Within their web-like nerve net, scientists found fused neurons. This is a peculiar arrangement that has never been observed in any other creature.

Maike Kittelmann, a cell and developmental biologist at Oxford Brookes University in the U.K., explains, “It means that there are other ways that neurons can connect to each other.” 

This unprecedented finding raises profound questions about the evolution of nervous systems and reignites the long-standing debate about the relationship between comb jellies and other members of the animal kingdom.

How the nervous system of the comb jellies work 

The discovery of the fused nervous system presented a lot of questions. For example, researchers wondered how this unique network develops and functions. 

While comb jellies lack brains, they possess a nerve net consisting of interconnected neurons. It is within this intricate network that the fused neurons were discovered. 

This peculiar arrangement suggests that comb jellies may have independently evolved their own nervous system, distinct from other animals.

The research focused on ctenophores in their early developmental stage when they are a few days old. At this point, these remarkable creatures can move freely and even reproduce, despite not being fully mature. 

The study revealed that the fused neurons form a structure called a syncytium, where the cell bodies and membranes merge, creating a continuous pathway.

The same cells that are fused still connect with other nerve cells through synapses, while other parts of the ctenophore nervous system rely on synapses exclusively. Simply put: comb jellies employ two different methods of communication between their nerve cells.

An advantage in tissue repair

One intriguing hypothesis put forth by Leslie Babonis, an evolutionary biologist at Cornell University, suggests that the fused nervous system in comb jellies might provide them with a remarkable advantage in tissue repair and healing. 

These creatures possess an astonishing ability to regenerate their entire bodies from small fragments of flesh. Could the fused network play a role in this extraordinary regenerative power?

“Maybe this is one of the secrets to their incredible ability for regeneration,” Babonis suggests, highlighting the potential link between the fused nervous system and the comb jellies’ remarkable regrowth capabilities.

However, it’s important to note that the study focused on only one species of comb jelly, Mnemiopsis leidyi, during one specific stage of its development. 

The research team plans to investigate other species of ctenophores and determine the full extent of this unique nervous system. 

If a significant number of ctenophore species possess similar fused nervous systems, it could provide support for the theory that comb jellies independently evolved their own nervous system separate from other animals. 

Understanding the evolution and diversity of nervous systems among different organisms has profound implications for our understanding of the human brain and neurological disorders.

Strange and mesmerizing creatures like comb jellies remind us that the natural world continues to surprise and astound us. There are many extraordinary tapestries of life on Earth.