Tuesday, May 18, 2010

It's a Frog's Life

The term amphibian comes from the Greek word amphibios which means both kinds of life. Amphibians have earned this name because for the most part they live on both land and in water. About 88% of amphibians are in the order Anura, which means tail-less or without tail, this includes approximately 5000 different species of frogs and toads. Frogs are different then other amphibians ( salamanders and caecilians) because as adults they have no tail and their legs are more adapted to jumping then walking.
Life for a frog typically begins in the water where the females lay thousands of eggs. Often the females will all lay their eggs at the same time, with many thousands of eggs around the chances of survival are better for the vulnerable eggs. Aquatic eggs generally hatch into tadpoles with in a week. The tadpoles are adept at life in the water with a tail to help propel them and gills to allow them to breath under water. Most tadpoles are herbivores, eating algae that they filter from the water with their gills. At this stage they are still highly vulnerable to predators such as fish, large dragonfly larva and birds.
As the tadpoles mature they begin to go through a gradual metamorphosis. They start by growing legs, back first and then front. At the same time that they are growing legs their lungs begin to form. Once they begin to breath air they spend most of their time near the surface of the water. In the later stages of their metamorphosis the tadpole develops the tools that it will need to change from a herbivore to a carnivore. The tadpole's small enclosed mouth expands to the same width as their head and develops weak teeth along their upper jaw called maxillary teeth, these are used mostly for holding their prey which they usually swallow whole. Their eyes shift forward and to the center, allowing for binocular vision which aids in the depth perception needed to catch prey. Internally their intestines shrink to a length more appropriate with their new diet. At the final stage of the metamorphosis the frog absorbs its tail through a process of programmed cell death called apoptosis. Once the tail has been absorbed the frog will begin its adult life. Its hard to tell how long a frog may live in the wild but in captivity some frogs have lived up to about 40 years. So it may be possible that this frog may still be hopping long after I am gone.


KaHolly said...

Wonderful, wonderful post today. I enjoyed the simple but clear explanation of the world of the frog and the accompanying photos. ~karen

Pam said...

Your great shots make life in a pond look wonderful, Eco. Isn't nature amazing!