Tadpole

A tadpole or polliwog is the larval stage in the biological life cycle of an amphibian. Most tadpoles live in water and have features like gills and tails that help them swim, similar to fish. As they grow, tadpoles go through a process called metamorphosis, where they change into their adult forms, developing lungs and losing their tails.

Some amphibians, such as certain frogs in the family Brevicipitidae, skip the tadpole stage entirely and develop directly from eggs into tiny versions of adults, called "froglets." In other species, tadpoles may hatch inside their mother’s body or stay in a special pouch until they transform.

Even though tadpoles have no bones, scientists have found fossils of them from the Middle Jurassic, showing that they have existed for millions of years. In some cultures, tadpoles are eaten as food and appear in many folk tales around the world.

Etymology

The word "tadpole" comes from old English words. It is made from "tadde," meaning "toad," and "pol," meaning "head." The word "polliwog" also has similar roots, combining "pol," meaning "head," with "wiglen," which means "to wiggle."

General description

All amphibians start life as larvae, which is a stage between being an embryo and becoming an adult. Most of these larvae are called tadpoles. Tadpoles look a bit like fish, with tails and gills, and they live in water. Frog tadpoles usually eat plants, while salamander and caecilian tadpoles eat other small animals.

Frog and toad tadpoles are round with compressed tails that help them swim. When they first hatch, they have external gills that later become covered by skin. As they grow, they develop legs, lungs, and change their diet from plants to small animals. Tadpoles come in many sizes and live in different water habitats, from ponds to fast-flowing streams. Some frogs even carry their tadpoles on their backs until they are ready to live on their own.

Fossil record

Fossil tadpoles, about 10 cm long, have been found in very old rock layers from the Upper Miocene. Even though tadpoles are soft and don’t have hard bones, they were preserved because of special films made by tiny living things. Some parts like jaws and bones turned into a thin carbon film.

One of the oldest known tadpole fossils comes from the Middle Jurassic period and belongs to a species called Notobatrachus deguistioi. Scientists discovered this fossil in 2024, showing how ancient these creatures are.

Human use

Tadpoles are eaten in some places around the world. In China, people collect large tadpoles from a special type of frog for food. In Peru, tadpoles are also gathered to use as both food and medicine.

Mythology and history

In the origin myths of the Wa people in China and Myanmar, the first Wa came from two female ancestors named Ya Htawm and Ya Htai. These ancestors spent their early lives as tadpoles, called "rairoh", in a lake called Nawng Hkaeo in their homeland.

In ancient Egypt, people used a picture of a tadpole as a special symbol in their numbers. This symbol stood for the big number of 100,000.