370 million years ago (that’s 37 followed by seven zeros!), a fish-like creature stalked the shallow waters of the ocean.
It had eyes on the top of its head, allowing it to remain submerged while looking out for its prey that lived above the water. It had fins that had turned feet-like, allowing it to wade instead of swim. Most importantly, it was developing lungs, allowing it to breathe air. This fish was evolving into the first amphibian.
Modern day amphibians come in all sorts of funky shapes and sizes.
The largest amphibian is the Chinese Giant Salamander (Andrias davidianus), which can grow up to 1.8 metres long! This salamander can only be found in one river in the whole world: the Yangtze River in China.
The flying frogs of Southeast Asia (Family Rhacophoridae), have large webbings around their toes that allow them to parachute themselves off trees, gliding from one place to the other.
The caecilian is a long, worm-like creature that could easily be mistaken for a snake, but upon closer inspection, you won’t find any scales. It is, surprisingly, also an amphibian.
Amphibians are cold blooded and commonly have smooth, moist skin. They use this as an additional method of breathing (in addition to lungs or gills). But amphibians may be best known for their multiple life stages. These life stages usually live in different habitats. For example, frogs lay their eggs in water, where they hatch into tadpoles, tadpoles are the larval stage of frogs!
As the frog matures into an adult, it loses its gills and develops lungs and legs, allowing it to emerge onto land.
The eggs that amphibians lay are quite unlike the eggs you have for breakfast; amphibian eggs have no shell! Instead, they are surrounded by a protective layer of jelly. Because it has no shell, amphibian eggs must be kept moist, to keep them from drying out. This is the reason many amphibians lay their eggs in water.
Amphibians of Singapore
In Singapore, we have two groups of amphibians: the Frogs (Order Anura) and the Caecilians (Order Gymnophiona).
Frogs are amphibians with long, muscular hind legs, webbed toes and no tails when they are adults. There are 27 recorded species of frog in Singapore. One of the most unique looking ones is the Malayan horned frog. Its distinct horns may look eye-catching in photos, but on the forest floor, it helps the frog blend in with the leaf litter around it.
Caecilians have elongated bodies, with no limbs (see above!). They also have grooves encircling their body called annuli. There are only two recorded species of caecilian in Singapore. Caecilians are very difficult to find due to their fossorial nature. As such, the number of times caecilians have been found in Singapore can be counted on one hand – only 4 times.
Singapore’s collection of amphibians may be limited, and the species we have may not be the prettiest. But what little we have left is precious and endearing in its own way.
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Most people seldom lay their eyes on a frog in our natural spaces. But their chorus echoes through the night as a stark reminder of their presence. They feed on pests like mosquitoes too. Needless to say, if amphibians do one day vanish, we would definitely notice.
Glossary
Order: A classification group for organisms below Class but above Family
Fossorial: A term to describe animals that are adapted to burrow and live underground