03/23/11

Spring to Life: From Tadpole to Frog

It’s finally Spring, and in our part of the world, we’re ecstatic. We’ve had a rough winter—we had snow and ice on our city streets every day for about 40 days in a row! The crocuses are blooming in my backyard, and outside the city, frogs are springing to life.

In a way, Spring is a good time to think about our “inner amphibian.” After all, mammals are descended from animals that moved from aquatic environments onto the land over three million years ago. As embryos, our heads in the early stages of development look remarkably similar to shark embryos—with gill arches and all. The metamorphosis of frogs is a process that’s not all that different from what all vertebrates go through, but the difference is that most of the development of birds, reptiles, and mammals—such as the growth of the lungs and limbs—takes place inside an egg or inside the mother instead.*

FROM EGG TO TADPOLE

A female frog first lays eggs underwater, sometimes hundreds of eggs, which form into a jelly-like clump called frogspawn, which floats on the water. Most of these eggs become food for other pond life, but some survive.

Tadpoles developing in eggs. © Dan L. Perlman/EcoLibrary.org

The tiny animal inside the egg grows for about a month, then hatches out of the egg. It looks like a small black fish and breathes underwater with feathery gills on each side of its head.

The tadpole’s tail begins to grow; it wiggles its tail to swim. Tadpoles are also called polliwogs. (The word “polliwog” is from Middle English polwygle. Pol means “head” and wiglen means to “to wiggle”). The tadpole eats algae and other plants that grow underwater.

Tadpole. Photo from Wikipedia.

FROM TADPOLE TO FROGLET

After several weeks, tadpoles begin their metamorphosis. Two tiny bumps appear near the tadpole’s tail—these will grow into back legs.

Two more bumps appear near the frog’s head—these will grow into front legs. Lungs begin to grow inside the tadpole’s body and the feathery gills disappear so that the tadpole will be able to breathe air.

The tadpole now has legs for hopping and walking, lungs for breathing air, but its long tail is awkward on land. Until the tail shrinks and is absorbed into its body, the froglet stays in or near the water.

Froglet with tail. Photo courtesy of www.scienceprojectlab.com

FROGLET TO FROG

When the tail is gone, the frog has completed its metamorphosis. The young frog will now feed on small insects, caught with their long, sticky tongues. It will eventually move away from the pond and find a safe place to grow.

This Spring, take some time to visit a nearby pond or swamp and see this process yourself. And check out the poster below that Susan designed for Earth Day, inspired by a photo by FROGS ARE GREEN photographer friend Joe Furman. All proceeds go to help our amphibian friends.

*I found this idea in Thomas Marent’s lovely and informative book, FROG.

03/3/11

Celebrating Spring Peepers! Tiny Frogs with a Mighty Voice

Now that it’s March, it’s almost time for the peepers to usher in spring!

Renowned science writer Carl Safina describes spring peepers so beautifully in his new book The View from Lazy Point: A Natural Year in an Unnatural World. I enjoy reading anything by Safina, who usually writes about the ocean, sea animals, or birds. He’s won many awards for his work, including the MacArthur “genius award.” Safina’s writing reminds me of Rachel Carson’s—very lyrical, yet not sentimental. In this book, he writes mainly about a year he spent in a cabin on Long Island. In the chapter, “March: Out Like a Lamb, ” he writes this about spring peepers:

I open a window to let in the season’s lushest, most delicious sound. It’s from tiny tree frogs that come to water to go a-courting—Spring Peepers. So far, these little amphibians remain abundant. And for as long as they’ve been, and as long as they are, their singing makes the difference between the night of winter and the breath of spring…

Hearing them is easy. Seeing them takes some effort. But even after I step into the shallows as deep as my boots allow, even though I hear calls coming from the half-submerged vegetation right around me—well within the halo of my flashlight—they’re all but invisible. They’re smaller than the tip of your thumb, colored like dead leaves. The majority of my neighbors—even many who were raised here— have never seen one. Many people assume the callers are crickets. But the sound and the season are so different, one might logically assume the moon is just the sun at night.

Safina goes on to describe how as a teenager he taught himself how to find spring peepers by following the sound into the woods at night, but they were very elusive. He finally found one and

…when that tiny movement caught my eye, I saw the littlest frog I’d ever seen, his bubble-gum throat puffed almost as big as his body, calling his heart out. That mighty sound from that tiny body appealed to my teenage sensibilities. His was a strong, clear voice, defiantly undaunted about being so small a soul in so big a world.

Spring peepers Safina writes are a “strong and joyous life-affirming presence” and he would

…gladly suffer a chilly bedroom just to open a window in spring when the peepers are at their peak, and let the exuberant trilling chorus resonate in my chest. “We’re alive,” they seem to say, “and time is short.” No sound in our region is so welcome and welcoming, so revivifying, as peepers in full spring chorus. Or so seemingly unlikely. Out of dust, God is said to have made one man. But here, out of mud, such song!

To celebrate peepers and spring, Susan created a poster for Earth Day 2011, with a wonderful photograph by Richard D. Bartlett. Enjoy!