Tadpoles Vulnerable To Drought
Congratulations (again!) to Kathie Fiveash, the first Naturally Curious reader to correctly identify the rough patch in Monday’s Mystery Photo as tadpoles that were stranded in a puddle that was drying up.
Most tadpoles acquire oxygen in a number of ways — through gills, through their skin, and by breathing air into their lungs. In this case, a lack of access to oxygen in the water has left them high and dry, as their lungs are not developed enough to provide them with the necessary amount of oxygen from the air. A sad ending for these young frogs, but a goldmine for scavenging raccoons, skunks, foxes and birds.
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American Toad Eggs Hatching
American Toads lay their eggs in double strings (one from each ovary) which can be three or more feet long and may contain 4,000 – 8,000 eggs. It doesn’t take long for toad eggs to hatch – just one week, or two at the most. The gelatinous strings begin to disintegrate, and tiny, dark tadpoles are released into the water. If nothing untoward occurs, the tadpoles will attach themselves to underwater vegetation or their egg mass for a few days, and hang vertically with their heads up.
Many aquatic predators, including Eastern Newts, consume both American Toad eggs and tadpoles. The pictured newt waited patiently nearby until tadpoles wiggled their way out of the gelatinous egg string and then immediately snatched and ate them. In another week toad tadpoles will be crowding the shallow shoreline water, and in two more weeks they’ll be metamorphosing into little toadlets.
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Green Frog Tadpoles Maturing
When 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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