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Green Frog Tadpoles Maturing

green frog with tail 127When you think about the structure and form of a tadpole, a plant-eating, streamlined creature designed for aquatic life, and that of a meat-eating terrestrial frog which is adapted for jumping on land, and know that they are one and the same organism, one can’t help but be impressed. The visible changes in this transformation are dramatic enough – legs emerging, head shape changing, tail being absorbed – but the internal changes a tadpole undergoes are just as dramatic. Research has shown that everything from a tadpole’s respiratory (gills replaced by lungs), urogenital and sensory systems to its digestive system (intestines becomes much shorter due to change in diet) is undergoing significant changes.

The length of time these changes take varies according to the species of amphibian. Most Green Frogs (Rana clamitans, pictured) undergo metamorphosis within the same breeding season or they overwinter as tadpoles and mature the following summer. (There are records of Green Frog metamorphosis taking up to 22 months). Biologists in Michigan found that eggs deposited before roughly June 25 were capable of developing in one season, whereas eggs deposited after roughly July 10 remained as tadpoles until the following year.

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6 responses

  1. Good morning, Mary! So… can we assume that this critter we see in your photo has functioning lungs, and has stopped being able to breathe under water? Is there a transition period where they can do both? (I do remember one year when I brought tadpoles into an aquarium in my classroom, and was horrified to find that some of them drowned because I had not provided any stones for them to climb onto, at the point when they could no longer breathe in the water.)
    I was in Cambridge, MA last week, and watched an impressive mass migration of THE TINIEST froglets I have ever seen, from one side of a wetlands path to the other. (They were no longer than half a millimeter.) Were they probably young peepers? Thanks! – Dell

    June 25, 2015 at 11:00 am

    • Yes, Dell, the pictured green frog had its head out of water, and the rest of its body under water. If you see all four limbs, it indicates that it is no longer using gills. I believe gills are functional until the fourth limb has emerged, but I may be wrong. Was the mass migration possibly recently-emerged American toads? They’re mighty small when they leave the water, and they do so all at once…

      June 26, 2015 at 4:54 pm

      • Huh. It never occurred to me that they might be toadlets, but maybe so. They were heading from the pond part of the wetland, toward the swampy zone, and you had to be careful not to step on one as you slowly walked the path.

        June 26, 2015 at 6:58 pm

  2. Kathie Fiveash

    Are green frogs and bullfrogs our only New England frogs that do not have a congress all at one time in the spring, like peepers and woodfrogs? What about leopard frogs and pickerel frogs and tree frogs? Poor Mary! Too many questions!

    June 25, 2015 at 12:42 pm

    • Hi Kathie,
      I am familiar with spotted salamander congresses, but if you mean a general gathering of one species, I think you’re right about peepers and wood frogs being the only species that are obvious about synchronizing their mating. It would seem that it would be beneficial behavior for any species, so maybe other frogs do it, but less dramatically?

      June 26, 2015 at 4:52 pm

  3. Miraculous transformation!

    June 25, 2015 at 3:32 pm

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