Tuesday, May 21, 2013

Egg Update

Learning about metamorphosis, or change, is such a rite of spring that many school children have done the whole tadpole thing four or five times by the end of third grade. Tadpoles are pretty sturdy and easy to acquire so teachers are assured that things will proceed in a predictable manner. Jumping on that bandwagon, I planned to do tadpoles with the preschoolers at Messy Fingers in April. Eggs, tadpoles, frogs seemed like a nice logical way to celebrate spring science.

So I expected my eggs,  collected in our pond just like the previous six springs, to proceed in a standard sort of fashion turning into tadpoles and then getting legs... well you know the drill. But here is where science took over.

The eggs seemed be in a much smaller mass than usual so I was concerned that something bad was happening. And the mass was thicker feeling but that could have been the cold, I thought.

The eggs hatched right at Messy Fingers much to the excitement of the parents.  But the "tadpoles" didn't seem behave in the usual way. They were jumpier almost more fish like in their movements. A week later, it was very very clear what critters I had in my container.


The external gills are a clear giveaway. Now this isn't entirely unexpected for two reasons. First every spring we hear wood frogs calling and they are an obligate species for vernal pools. Now that is a lot of big words and new ideas for one sentence. Vernal pools are ponds that are generally wet only in the spring so no fish live in them. This special wetland area is home to many unusual species that are obligate species, meaning they can only breed in a vernal pool.

And second, we found a baby spotted salamander in our back yard two years ago. They don't travel far from their birthplace and are also an obligate species.

Check out this website from Maine on Vernal Pools. They have a great coloring page comparing frogs and salamander life cycles.

The babies are going to have to go back to the pond very soon. Salamanders use the chemistry of the pond to find it again when they are adults and will only lay eggs in the pond they hatched in. I've been very careful to only put water from that pond in their tank.

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