Professor JĂ©kely believes that a peptidergic signalling system allows a very high complexity of behavioural organisation.
He said: “Each peptide can be used individually as a different signal, but the peptides could also be used sequentially or together in different combinations which allows for very high numbers of unique signals between cells. This explains how Placozoans can coordinate sophisticated behavioural sequences such as feeding.”
The new study explored how this multicellular animal with no nervous system can coordinate all the cells in its body to perform complex behaviour.
They found that Placozoan cells contain a variety of small peptides, made up of 4-20 amino acids that are secreted from one cell and detected by neighbouring cells as a means of communication.
Associate Professor Dirk Fasshauer, from the University of Lausanne, Switzerland and co-author of the study said: “These new findings show that outer appearances can be deceiving, because cells that look the same are actually signalling with different molecules and are very likely to have different functions.”
When I read this stuff, I can really see why ID is so popular among the public. You may have an explanation for how this can come about, and why it is that it works this way, but that a kind of organism, three cell layers thick, can possess this kind of elegance, articulation, instruction, reception and response, all obviously coordinated to perform specific functions at specific times is utterly awe inspiring.
I don’t know how it is truly insight into the evolution of the nervous system, because it has no nervous system, but it is amazing, indeed.
Honestly, I wish that they would have described the “signaling” in more detail. Does one peptide induce a chemical response in a cell (as in a chemical reaction) to crinkle, turn, flatten, churn, etc., or does the peptide, as they suggest in the article “signal” the cell’s response? I think that would be an interesting aspect to know.
The abstract explains the relevance to evolution:
[The placozoan] genome contains genes encoding several neuropeptide-precursor-like proteins and orthologs of proteins involved in neurosecretion in animals with a nervous system
…
Together, the data demonstrate a crucial role for peptidergic signaling in nerveless placozoans and suggest that peptidergic volume signaling may have pre-dated synaptic signaling in the evolution of nervous systems.
A nervous system needs a way for cells to communicate with each other over short gaps, and this is exactly what these peptides do in placazoa.
From what I have read, the peptides bind to receptors on the surface of neighboring cells. The intracellular portion of the receptor can then cause changes within the cell. You can think of it like a Rube Goldberg apparatus where the binding of the peptide to the surface receptor gets the whole thing going.
Very cool! Thanks for the explanation. So, it seems then that the article is probably correct as it is phrased in that the peptide is “signaling” one action or another, the receptor is passing along the message, and then some other interaction causes the appropriate action to occur? Such that the peptide is actually a code or signal?