Monday, September 06, 2010

The metamorphosis of a frog

When I was a kid at school, I remember that the science teacher explained us the life cycle of a frog and how it evolves from an egg to an adult frog. At this time I did not have any special interest in frogs or toads.
When I started collecting stamps about frogs I wondered is the various steps of a frog metamorphosis would be somehow pictured on stamps. As you will see this is rarely the case. But I found recently a set of six cancellations from South Korea illustrating the complete life cycle. I could not find any detailed information about these cancellations and in which context they were used but I think they are really impressive. If you have any information about them I would be very happy to hear from you.

The life of frog starts with an egg. Females can lay several thousands of eggs, usually in the water. Frogs lay eggs in masses while toads usually lay eggs in long chains. The eggs are fertilized by the male.

After a short time life starts when the central yolk splits in two, then four, then eight… After a period between 6 and 20 days the eggs hatches and a tadpole is born. At this time a tadpole is made of gills, mouth and a tail.

After several weeks (6 to 9) legs start to sprout and grow.

By 12 weeks the tadpole has evolved into a froglet, a small version of the frog with a tail

By 16 weeks the frog leaves the water to start its new life of adult.

Frog eggs are very seldom on stamps. I know only two stamps picturing frog eggs.
The first one is a 1975 stamp from Spain picturing an Alytes obstecticans.

The particularity of this frog species is that the male sticks the eggs on its legs (as shown on the stamp) and keeps them form several days like that, putting them in water once a day.

The second stamp is one from Netherlands issued in 1976 that pictures a European green frog (formerly known as Rana esculenta and now known as Pelophylax kl. esculentus) surrounded by eggs.

As far as tadpoles are concerned I know only this stamp from China issued in 1980 and picturing the painting “Tadpoles in a stream” from the Chinese painter Qi Baishi.

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