From spawn, to tadpole and finally, frog, the early life of a frog is truly fascinating. Watch the metamorphosis unfold in this film shot in my garden pond.
Metamorphosis
To capture the metamorphic process of a frog, I turn the spotlight on my garden pond and film the eggs, spawn, hatching and finally the journey to fully formed frog. The common frog species, or Rana temporaria, can be found across Britain.They share my pond with an array of species, including toads, newts and a wide number of invertebrates.
Frog egg
Each spring adult frogs migrate back to my pond to lay their eggs in their thousands. These eggs are encased in a protective jelly filled with nutrients and the male sprays these with his sperm. The spawn then expands in water and has enough nutrients contained within it to feed the tadpoles during their first days. Interestingly the jelly is attached to pond weed which prevents it from sinking to the bottom.
Cell division
It's incredible to watch the process as the frog spawn begins to develop. Each starts as a single fertilised egg known as a zygote. This cell contains a mixture of the parent frogs DNA. Through a process known as mitosis, this cell copies its DNA and then splits into two; a copy of the DNA mix in each identical daughter cell. Over the next few weeks this happens millions of time until a fully-developed tadpole is ready to break free from the jelly.
Tadpoles
At this stage they eat just algae and plant matter, but now they undergo a remarkable metamorphosis. They grow back legs, then front ones. As they develop, skin begins to grow over their feathery gills. Their diet also changes and they become carnivorous, eating water fleas and other invertebrates. Sometimes, if conditions are too crowded, they'll even eat each other!
These tiny tadpoles are extremely vulnerable to predators. Aquatic beetles like back swimmers will gobble them in a moment. But the lucky ones continue to develop, hiding under the pond weed.
Froglets
When the froglets finally emerge they seem so tiny, but already their lungs have developed and they are ready to venture out of the pond. They will continue to grow for up to four years and, interestingly, individuals often return to the very same pond they were born in. So I'm hoping I'll see these frogs again!
