3 ms·
I can't make sense of this: "Moroz reached this conclusion by testing the nerve cells of ctenophores for the neurotransmitters serotonin, dopamine and nitric o
by tempguy9999 7y ago
I can't make sense of this:
"Moroz reached this conclusion by testing the nerve cells of ctenophores for the neurotransmitters serotonin, dopamine and nitric oxide, chemical messengers considered the universal neural language of all animals. But try as he might, he could not find these molecules. The implications were profound."
But plants make and use serotonin and dopamine
Phytoserotonin also plays a role in the following aspects of plant function:
Growth regulation
Xylem sap exudation
Flowering
Ion permeability
Plant morphogenesis
Regulation of ripening
from https://www.news-medical.net/health/Serotonin-in-Plants.aspx https://www.news-medical.net/health/Serotonin-in-Plants.aspx
and
The functions of plant catecholamines [seems to be a ref to dopamine] have not been clearly established, but there is evidence that they play a role in the response to stressors such as bacterial infection, act as growth-promoting factors in some situations, and modify the way that sugars are metabolized. The receptors that mediate these actions have not yet been identified, nor have the intracellular mechanisms that they activate
from https://en.wikipedia.org/wiki/Prolactostatin#Plants https://en.wikipedia.org/wiki/Prolactostatin#Plants and
Plants and animals diverged ~1.7 billion years ago, which is plausibly why they share these neurotransmitters, yet the article seems to say we diverged from ctenophores ~ 0.5 billion years ago "If Moroz is right, then the ctenophore represents an evolutionary experiment of stunning proportions, one that has been running for more than half a billion years"
So unless serotonon and dopamine evolved in plants and animals after the split between plants and animals, (or somehow ctenophores lost these after they split from us) how is this possible?
- mannykannot 7y agoIn evolution, the current uses of a given structure or molecule is not necessarily an indication of what it originally evolved for, and in this case, whatever plants have been doing with serotonin and dopamine, it is not as neurotransmitters. When animals began to evolve neural systems, presumably these already-present molecules proved useful as neurotransmitters. The fact that ctenophores use a different set of neurotransmitters is taken by Moroz as strong evidence that neural systems evolved more than once - and furthermore, according to the article, "Moroz now counts nine to 12 independent evolutionary origins of the nervous system" on the basis of other differences. In this view, ctenophores are the last representatives of one of those alternatives. I wonder if Moroz is harming his case by stretching it too thinly -- small differences do not necessarily require independent origins -- but I am not a biologist.
- SamBam 7y agoIt looks like you are correct in your assumption that serotonin evolved in the common ancestors of plants and animals, instead of being convergent evolution. [1],[2] So it would seem as if the ctenophores lost the ability to produce these chemicals, and went on to develop a nervous system that didn't require them. But the article is really about the evolution of the nervous system, and so the pertinent question is whether (a) the evolution of the nervous system was more recent than 0.5B years ago, in which case the two nervous systems evolved independently, or whether (b) the nervous system evolved earlier than that, and then the evolution of the ctenophores adapted its nervous system to not require serotonin and dopamine. I think the article is suggesting (a). 1. https://www.sciencedirect.com/science/article/pii/S1569733910700692 https://www.sciencedirect.com/science/article/pii/S156973391... 2. https://en.wikipedia.org/wiki/Serotonin#Comparative_biology_and_evolution https://en.wikipedia.org/wiki/Serotonin#Comparative_biology_...
- ncmncm 7y agoEvidently ctenophores don't use serotonin anymore, and have found some other molecule they like better for what they are doing. There is nothing special about the molecules we use, they just happen to fit the receptors we use, so switching would require changing both, which is too hard to bother with. If you haven't watched youtube videos of ctenophores eating one another yet, you are in for a treat.