Dear Readers, following all the excitement about frogs and newts yesterday, I thought I’d dig into the archives of New Scientist and see what I could find to share with you on the subject of tadpoles. One question that I’ve always had is – why do some tadpoles mature as expected and turn into baby frogs or toads, and why do some seem to spend the winter as tadpoles? This very question was asked in New Scientist in 2018, and the answers were most interesting.
One obvious answer that occurred to me is that, as climate change makes for warmer winters, amphibians overwinter as tadpoles simply because they can: if they can get a jump (see what I did there) on the newly-hatched spring tadpoles, they will have a ready source of food (sadly many species of frogs are cannibals). However, I know from my own endeavours that frogs seem to mature according to the water temperature – when I brought some tadpoles indoors because there were problems in their pond, they grew legs several weeks before their ‘wild’ relatives. So can frogs ‘choose’ when to metamorphose?
It also seems to me that in a population of tadpoles, if some mature quickly and some slowly they are covering all eventualities – whatever the winter weather, some will survive. That’s how evolution works, after all.
Another suggestion was that the rate of maturation can be delayed by imperfect conditions in the pond – overcrowding, and hence lack of food, or low water temperature will all slow things down.
But finally one lady, who is definitely a soulmate, used to observe the development of the tadpoles in her garden over seventy years ago. She returned home after the school holidays to find that the tadpoles all had four legs but still had a tail, and that it was long past time when they should be fully-developed. She had a nature book by Enid Blyton (better known for Noddy), and found that tadpoles needed iodine to mature, presumably because of its influence on thyroid hormones. Medicine cabinets used to hold iodine for cuts and grazes in those days, so she put a few drops into the pond.
‘Days later, the garden was teeming with froglets’.
Fascinating stuff. I remember treating a goldfish who had a fungal disease with a few drops of iodine, and it cleared that up too.
Now, here’s something amazing.
Newly-hatched tadpoles need to breathe air, but are too weak to puncture the surface tension of the water. So, instead they suck at the surface of the water from below so that they break off a bubble which contains fresh air from the outside world. They breathe this in to their lungs and then exhale it out. And furthermore, you can watch it in the article below.
And finally, it appears that in Egyptian hieroglyphics, a tadpole represents the number 100,000. Who knew?
Photo One by Miika Silfverberg from Vantaa, Finland, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons
Photo Two from https://twitter.com/yara_haridy/status/1200769342952083456