faster metamorphosis in Triturus cristatus

France, British isles

faster metamorphosis in Triturus cristatus

Postby Will Atkins » Mon Jul 27, 2020 1:27 pm

In the UK crested newts are protected as a rare and declining species. One problem they have is slower metamorphosis times which means they need more permanent ponds for breeding than smaller newt species. However they cannot tolerate fish which are often present in more permanent ponds - 'catch 22'.

At two sites that I monitor I have found smaller than usual GCN metamorphs - c4cm rather than 6-7cm. They have the dark skin and gill stubs of metamorphs and they walk, rather than wriggle (all characteristic of metamorphs rather than larvae) earlier than usual - mid July rather than mid August - early September which was traditional for metamorphosis time in southern England 20 or 30 years ago. The ponds have dried up, so any remaining larvae would be killed.

Now for the question: I wonder if this rapid metamorphosis is due to:

1 - warmer water allowing faster development

2 - natural selection for individuals with faster metamorphosis (and their offspring)

3 - phenotypic plasticity - ie larvae 'choose' to metamorphose earlier as they detect falling water levels and imminent death.

Does anyone have any thoughts or literature they know of that could help with this? Thanks in advance!
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Re: faster metamorphosis in Triturus cristatus

Postby Michal Szkudlarek » Sun Aug 02, 2020 7:28 am

Maybe all of these 3 things play a role?
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Re: faster metamorphosis in Triturus cristatus

Postby Will Atkins » Sun Aug 09, 2020 3:32 pm

I'm sure you are right, I'd love to know if all 3 are equally important... Here's a link to a photo taken today of another site where the water often evaporates before metamorphosis is possible, but this year it looks like they were lucky!

https://www.flickr.com/photos/100121190 ... en-public/
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Re: faster metamorphosis in Triturus cristatus

Postby Michal Szkudlarek » Mon Aug 10, 2020 11:26 am

Beautiful photo Will. I have never seen so many juvenile Crested Newts at once. Did you find them under man-made cover? Has the UK leaving the EU impacted conservation of that species?
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Re: faster metamorphosis in Triturus cristatus

Postby Will Atkins » Wed Aug 12, 2020 7:40 pm

Thanks Michal! they were all under a single piece of wood beside the dried up breeding site - and I also found dozens of others under other pieces of timber. We haven't officially left the EU yet - maybe some global catastrophe will persuade our politicians that we should stay after all ... ;) But if the worst comes to pass then I fear for our great crested newts given that our 'leader' Boris has recently accused them of being a major obstacle to building projects in the UK...
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