Whom did cnidarians arm agains?


by haael
Tags: agains, cnidaria, cnidarians, evolution, predator
haael
haael is offline
#1
Feb23-14, 07:58 AM
P: 397
Hey. I'm not a biologist, but I love to read about the evolutionary origins of different species. I also realized that the current knowledge on this matter is still incomplete.

Now, when reading Wikipedia about cnidarians, ctenophora and other primitive types, I started to wonder. Cnidaria and ctenophora are very similar, so they are likely related, but it is still not known which type came first.

I suddenly came up with a theory. We know that cnidaria have the poisonous cells filled with neurotoxins. They are rarely used as an offensive weapon, rather as a defense. Doesn't it mean that they evolved from an evolutionary pressure of some predators that had must have had neurons?

Defensive weapon implies existence of some predator. The target of the poison (neurons) means that the predator must have had neurons.

So, that means that cnidaria are more advanced than ctenophora and their predecessor more likely resembled ctenophora than the other way.

We could also approximate the time when it all happened. The apperance of cnidaria must have occured shortly after the apperance of predators with neurons.

Does this chain of thought have any probability of being true?
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Enigman
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#2
Feb23-14, 01:13 PM
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P: 547
Ctenophora came first according to:
The Base of the Animal Tree?

The identity of the most basal lineages of the animal kingdom evolutionary tree has long been contested. Ryan et al. (p. 10.1126/science.1242592; see the Perspective by Rokas) sequenced the genome of the ctenophore the warty comb jelly or sea walnut, Mnemiopsis leidyi, and conclude that ctenophores alone, not sponges or the clade consisting of both ctenophores and cnidarians, are the most basal extant animals. The results suggest a specific evolutionary process that likely occurred—including repeated gains and loss of mesoderm, expansion of genes associated with the cell cycle, growth signaling, apoptosis, and epithelial and neural cell types. Furthermore, previous hypotheses regarding the evolution of animals may require re-evaluation.
http://www.sciencemag.org/content/342/6164/1242592
(Editor's summary)


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