A Truly Amazing Body Makeover
Amphibians all begin with an aquatic phase and then go through metamorphosis to their adult terrestrial phase. So what goes on in metamorphosis? Taking frogs as an example what happens in the massive body makeover by which the tadpole body morphs into a frog? The genes which control metamorphosis are already present in a tadpole, but their expression is inhibited by factors which affect the thyroid hormone. The exact mechanism of this process is still an area of active research
When the tadpole reaches a sufficient size then the inhibitors become inactive, the development genes are activated by the thyroid hormone and metamorphosis can go ahead. There is a complex sequence of specific cell death and selective cell proliferation. These changes cause the resorption of the tail providing energy so feeding can pause and the growth of leg ‘buds’ can begin. However this is just the start. The tadpole has to convert from a plant based diet to that of a carnivore. The simple tube digestive system is transformed to something much more like our system with stomach, duodenum and intestine. The head grows larger in proportion to the body with a new articulated jaw and a muscular long tongue, which is able to capture the new invertebrate prey. The re-engineering continues with a new three chamber heart and air breathing lungs so the frog can lead a terrestrial lifestyle and it all takes about a week or so to accomplish! The complex mechanism is actively studied not just for its intrinsic interest, but also because similar processes can be identified in human embryo development Sussex Native Amphibians
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Common Toad Bufo bufo Photo by Barry Kemp
The common toad can grow up to 13 cm in length for females, males up to 8 cm. Their coloration is more consistently brown, although orange or nearly black animals can occur. The skin is warty, and there are twoclearly pronounced glands behind the eyes. Their legs are relatively short, and toads tend to walk or hop rather than leap. Toads lay eggs in strings of spawn often wrapped around submerged vegetation. Toad tadpoles are almost black and uniform in colour.
 Photo by Barry Kemp
Common Frog, Rana Temporaria
The most familiar of our amphibians, the common frog can grow up to around 10 cm in length. Their coloration is very variable, as are the markings. Most frogs are greenish, brown or grey, although yellow, orange and red animals can occur. There is a dark mask behind the eye, and the skin is smooth and moist. Frogs lay eggs in clumps of spawn that float just below the surface of the water. Tadpoles are dark brown but with clearly defined golden speckles. 
Smooth Newt Triturus vulgaris
 Photo by Barry Kemp
The smooth newt adults are between 6 and 10 cm in length. During the breeding season males acquire a high undulating crest along the back and tail. Their coloration is consistently brown with dark spots. The belly is yellow to orange with dark blotches. In both males and females there are spots on the throat. Smooth newts lay eggs singly on the leaves of aquatic plants. Smooth newt tadpoles (efts) have external gills and are indistinguishable from palmate newt larvae
Palmate Newt Triturus helveticus
 Photo by Barry Kemp
The palmate newt adults usually reach about 7 cm in length, and rarely up to 9cms. Males have more of a ridge than a crest along the back. They also develop complete dark-coloured webs between the toes of the hind feet, and a short thread-like tail filament from a truncated tail end during the breeding season. Their coloration is brown to olive-brown with a pale straw to orange belly. In both males and females there are few if any spots on the throat. Palmates lay eggs singly on the leaves of aquatic plants
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