Innovations in Biotechnology and Medical Sciences

Study reveals unique Nervous System in Comb Jellies


From UPSC perspective, the following things are important :

Prelims level: Comb Jellies, Neurons, Neural Network

Mains level: Not Much


Central Idea

  • Comb jellies, or ctenophores, are marine animals with jelly-like bodies and iridescent combs.
  • They represent an ancient animal lineage and have a distinct nervous system.
  • A recent study published in Science examined the comb jelly nervous system and made surprising discoveries.

What are Comb Jellies?

  • Comb jellies, also known as ctenophores, are marine animals that belong to the phylum Ctenophora. They are fascinating creatures with a unique and delicate appearance.
  • Despite their name, comb jellies are not actually true jellyfish.
  • They have a gelatinous, transparent body that is often luminescent and adorned with rows of cilia, or comb-like structures, which give them their characteristic shimmering appearance.

Findings of the new study

  • The researchers aimed to investigate how nerve net neurons in comb jellies connect.
  • Contrary to expectations, synapses (junctions between neurons) were absent in the nerve net.
  • Instead, nerve-net neurons were continuously connected by a single plasma membrane.

Significance of ctenophores

  • In the 1950s, electron microscopy confirmed the separate-cell nature of neurons connected by synapses.
  • Ctenophores challenge this notion by having a syncytial nerve net, as observed in the new study.
  • Ctenophores attracted attention due to their status as a potential early animal lineage.
  • Whole-genome sequencing studies supported the theory that ctenophores branched off early in animal evolution.

Evolution of ctenophore nervous systems

  • The evolution of ctenophore nervous systems remains unclear to biologists.
  • Leonid Moroz proposed a controversial theory of independent nervous system evolution in ctenophores and other animals.
  • Ctenophores exhibit a unique nervous system lacking classical neurotransmitter pathways and common neuronal genes.
  • The absence of muscle-based movement and reliance on cilia might have driven the evolution of a different signal conduction system.

Questions for further research

  • Researchers aim to study the development of nerve net neurons in ctenophores.
  • They seek to determine if adult ctenophores retain syncytial nerve nets or develop synapses.
  • The uniqueness of ctenophore nervous systems provides valuable insights into the evolution of the nervous system.
  • Comparative analyses of unique animal systems like ctenophores aid in understanding neuronal function and treating disorders.


  • Understanding the functional and evolutionary significance of syncytial nerve net neurons in ctenophores requires further research.
  • This study serves as a crucial foundation for investigating the evolution of nervous systems in animals.
  • Comparative studies on small marine creatures like ctenophores offer insights into the fundamental principles of brain function.

Key Terminologies

  • Ctenophores: Another term for comb jellies, referring to marine animals belonging to the phylum Ctenophora.
  • Nerve Net: The diffuse nervous system found in comb jellies, composed of interconnected neurons.
  • Synapses: Junctions between neurons that allow for communication and transmission of signals in most animals, including humans.
  • Plasma Membrane: The outer membrane of a cell that separates its internal components from the external environment.
  • Neurotransmitter Pathways: The specific chemical signals used by neurons to communicate with each other in the nervous system.
  • Syncytial Nerve Net Neurons: Neurons within the nerve net of comb jellies that are interconnected without the presence of synapses.
  • Colloblasts: Specialized cells in comb jellies used for capturing prey by producing adhesive substances.

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