Comb Jellies Uniquely Evolved91ׯ to Sense Their World91ׯ

In 2023, the ctenophore made a splash, surprising researchers at the MBL with its bizarre biology.91ׯ91ׯ&Բ;
Ctenophores, also known as comb jellies, are gelatinous invertebrates that beat their iridescent combs as they swim through the water. They91יre an ancient animal, with over 700 million years of evolutionary history.91ׯ91ׯ&Բ;
Studying our oldest ancestor is like 91לlooking into a window to the past,91ם said Oscar Arenas Sabogal, a postdoctoral scientist at the University of California, Berkeley, and Grass Lab associate director at MBL this summer.91ׯ&Բ;
For millions of years, comb jellies have brought with them an odd mix of parts and wiring 91ד a physiology completely their own.91ׯ91ׯ&Բ;
With a body plan worthy of a 91לsea alien,91ם the organism seemed all the stranger when fellows at the Grass Lab gazed upon one that had two mouths. Perhaps, they hypothesized, this was a Frankenstein creation of two jellies that had spontaneously fused as one.91ׯ91ׯ&Բ;
Systematic tests confirmed their suspicions. Almost every time researchers spliced and combined tissue samples from two different jellies, a newly fused ctenophore emerged a few hours later, each specimen rearranging its biology to accommodate that of the other.91ׯ91ׯ&Բ;
It was more than a patchwork mosaic of tissues and cells, superficially cut and pasted; it was a complete reorganization.91ׯ91ׯ&Բ;
For example, researchers watched the two digestive systems merge into one functioning tract: Food sent through one mouth seamlessly traveled to the other91יs gut. The two jellies also moved as one, synchronizing their contractions to coordinate a startle response.91ׯ91ׯ&Բ;
Based on these behaviors, it91יs possible that the nervous systems integrated in the fused ctenophores 91ד a feat 91לunheard of,91ם Arenas Sabogal said. If true, 91לit could have huge implications for regeneration, compatibility of tissues, and cell recognition systems.91ם91ׯ&Բ;
A 91לweird91ם nervous system91ׯ91ׯ&Բ;
Scientists don91יt know much about the ctenophore nervous system, but 91לthe more we investigate, the weirder it gets,91ם Arenas Sabogal said.91ׯ91ׯ&Բ;
In vertebrates, individual neurons are arranged in a network buzzing with information. The neurons communicate sequentially, releasing a chain of chemical and electrical signals from one to the next throughout the neural circuit.91ׯ91ׯ&Բ;
Comb jellies, however, assemble their machinery differently. These creatures develop individual neurons as expected, but later, those neurons fuse and mesh together, forming a net of cells.91ׯ91ׯ&Բ;
This summer, Arenas Sabogal is peering into the ctenophores91י puzzling physiology and running studies to determine how the nervous system transforms sensations into behavior. 91לBecause they91יre so different, there91יs a possibility that they91יre doing completely new stuff,91ם he said.91ׯ
A mechanical sense91ׯ&Բ;
To ctenophores, the world is rich with sensations. They detect mechanical stimuli, perceiving the environment through changes in water pressure, gravity, and balance. But how does the animal detect these mechanical cues 91ד or rather, how do their mechanical senses work?91ׯ91ׯ&Բ;
Molecular data suggest that one type of gene, piezo, may be connected to mechanosensation in ctenophores.91ׯ&Բ;
Piezo genes are mechanical receptors that encode a type of protein known as an ion channel. These help convert mechanical stimuli into cellular signals 91ד a conversion that reveals useful information about the environment to the animal.91ׯ91ׯ&Բ;
Since showing piezo channels are present in ctenophores, Arenas Sabogal has measured their activity in some tissues sensitive to mechanical stimuli. He also investigated them in cells called balancers, which are part of a gravity-detecting complex and give the animal a sense of up and down.91ׯ91ׯ&Բ;
Piezo91יs presence throughout the organism gave Arenas Sabogal 91לa good hunch that [the piezo channel] was going to be the mechanosensor,91ם so he developed several experiments to test how these ion channels work in ctenophores. Early results suggest that the ctenophore ion channels are incredibly conserved, persisting through 750 million years of evolution.91ׯ91ׯ&Բ;
Intelligent design91ׯ&Բ;
Scientists first sequenced the ctenophore genome a, which led to striking discoveries about its nervous system. Since then, it91יs largely accepted that ctenophores are the ancestral organism, evolving earlier than either sponges or cnidarians (jellyfish). This implies one of two scenarios about its nervous system, Arenas Sabogal said.91ׯ91ׯ&Բ;
The first suggests that the nervous system traveled a fragmented evolutionary path, being lost in sponges and popping up again in cnidarians before continuing.91ׯ91ׯ&Բ;
The second proposes that the ctenophore nervous system evolved independently from cnidarians. In this scenario, ctenophores evolved an entirely unique way of perceiving and acting in the world, carving their own path to complex behavior.