[Taxacom] Tardigrades ----> to Nematodes
mivie at montana.edu
mivie at montana.edu
Tue Feb 16 14:54:25 CST 2010
Please be careful how you phrase these things, as while "a fanciful mind"
may be a put down, it can also be the creative source of untested but
useful hypotheses by those who think three dimensionally but lack the
resources to do the tests themselves. Let us say that Kenman's ideas are
nothing but what Gould called "just so stories." Even then, if someone
looked at the genes for trehalose in mosses, tartigrades and nematodes,
and found them identical, wouldn't that be interesting? If they were
totally different in approach, wouldn't that also be interesting? How do
you lose by taking interesting but fanciful ideas and testing them?
> Wow, sounds fascinating. I am only wondering if this is based on science
> or a fanciful mind. How did the tardigrades acquire the moss gene ?
>> Dear All,
>> Isn't it interesting that tardigrades and nematodes are among the
>> few animals able to enter cryptobiosis, especially when threatened by
>> extreme desiccation. I would suggest that some clade of tardigrades
>> acquired genes for the production of trehalose sugars from primitive
>> land plants (such as mosses). Both groups would have faced the same
>> problem of desiccation as they invaded land environments during the
>> early Paleozoic.
>> I propose that tardigrades in turn passed these "trehalose genes"
>> on to their nematode descendants, thus enabling them to also take
>> advantage of cryptobiosis as a survival strategy. Something to look for
>> when comparing nematode and tardigrade genomes.
>> --------Ken Kinman
>> P.S. If tardigrades evolved from arthropods, as I suspect, did they
>> evolve from crustaceans or from chelicerates??? Both of these arthropod
>> groups give rise to terrestrial forms with reduced number of legs.
>> Modern tardigrades have four pairs of legs like many arachnids, but the
>> known fossil tardigrades from the Cambrian of Siberia were apparently
>> hexapodous. But then again, I suspect hexapody may have arisen
>> independently more than once from crustaceans. Therefore, the exact
>> number of legs may not be definitive, except that perhaps reduction to 3
>> or 4 pairs of legs may somehow be particularly advantageous on land
>> given the high diversity of hexapods and arachnids on land.
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