Good evening. Please write an essay with full citations on one of the following topics:


c) Please write a report on the following article: "Alien-like Comb Jellies Have A Nervous System Like Nothing Ever Seen Before."


Report:


Comb jellies, or ctenophores, are marine animals that belong to a phylum of around 200 species. They are characterized by their transparent or translucent bodies, their eight rows of cilia that resemble combs, and their bioluminescence. They are also known for their peculiar nervous system, which differs from that of any other animal.


The nervous system of most animals consists of neurons that communicate with each other through synapses, which are gaps where neurotransmitters are released. However, comb jellies have a different way of connecting their neurons. Within their nerve net, which is a web-like network of neurons that spans their body, some neurons are fused together, forming a structure called a syncytium. This means that the cell bodies and membranes of these neurons are merged, creating a continuous pathway for electrical signals.


This discovery was made by researchers from Oxford Brookes University in the U.K., who studied ctenophores in their early developmental stage, when they are only a few days old but can already move and reproduce. They used electron microscopy and immunofluorescence to visualize the structure and function of the nerve net. They found that the fused neurons are present in the nerve net of all ctenophore species they examined, suggesting that this feature is ancestral and not a result of convergent evolution.


The researchers also found that the same cells that are fused still connect with other neurons through synapses, and that other parts of the ctenophore nervous system rely on synapses exclusively. This implies that comb jellies use two different modes of communication between their neurons, which may have different advantages and disadvantages.


The significance of this finding is that it challenges the common assumption that the nervous system of animals evolved only once, after sponges diverged from the rest of the animal kingdom. Some scientists think that ctenophores branched off early and evolved their own nervous system independently from other animals. The presence of fused neurons in comb jellies may support this hypothesis, as it indicates that there are other ways of forming a nervous system besides using synapses.


However, this question is still unresolved, as there are conflicting evidence and arguments about the phylogenetic position of ctenophores and the origin of their nervous system. More research is needed to understand how the fused neurons develop and function in comb jellies, and how they compare to the synapses in other animals.


References:


- Alien-like comb jellies have a nervous system like nothing ever seen before | Live Science

- Alien-like comb jellies and their mysterious nervous system

- Comb Jelly Facts (Ctenophora) - ThoughtCo


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