How does a spawn turn into a frog?

1. Egg

Several layers of absorbent watery jelly swell to protect a single tiny embryo that has been fertilised by the male frog. Water is vital to the development of these aquatic babies.

2. Mutation

Following a mere matter of hours after the egg has been laid, the metamorphosis has begun.

3. Tail bud

The tail bud forms at around the four-day mark. Muscles have begun to develop and the embryo feeds on the yolk inside itself.


At six days old, the egg hatches and becomes a tadpole. External gills develop to filter water and take in tiny bits of food. A sucker protrudes beneath the head end, which can suck onto plant matter.

5. Internal grills

Nine days into metamorphosis, a flap of skin grows over the external gills and replacement internal gills develop. A spiracle (pore) remains on the left-hand side where water can escape. The tadpole’s eye is not yet fully formed.

6. Hind legs

Next the internal grills develop and a pair of hind legs form.

7. Front legs

The final stage of a frog’s development (around 75 days) includes the arrival of  front legs and lungs to replace the internal gills. Amphibians can also breathe through their mucous-covered skin.

8. Froglet

For the next one to two years, the young frog’s tail will become increasingly short until it’s barely a tail at all

9. Frog 

A frog becomes an adult at the tender age of three years. It will breathe using its fully formed lungs and will take to the land to seek out a mate and begin the whole process again.