Thursday, July 26, 2007

Mudskippers: frog, snake or fish?

Thoughtful question: "Is it a fish, a snake or a frog?".

Fish! "Yes, it's a fish. But how can it move around out of water? How do you think it breathes out of water?"

"How do YOU breathe underwater when you go diving?"

"Just like the way we bring two tanks of air for scuba diving, the fish brings two tanks of water in its gill chambers. Which is why it has such 'puffy cheeks'."

Naked Facts

Mudskippers have to regularly replenish the water in their gill chambers, so they cannot stay far from water. But mudskippers can actually ‘breathe’ (absorb) air through their skin (as long it remains moist) . This is why they often roll in puddles and keep their tails in water, leading some early observers to believe that mudskippers breathed through their tails!

Mudskippers skip by flipping their muscular bodies. They skim over mud as well as the water surface. They can catapult themselves for a distance of up to 60cm and actually move faster on land and on the water surface than by swimming with their bodies in water.

A distinctive and endearing feature of mudskippers is that their huge goggly eyes at the top of their heads. Unlike other fishes, mudskippers prefer to swim with their heads above water, thus giving them a good 360 degree view.

Corny Joke: Their eyes are like a CCTV in action.

Interesting Fact: Mudskippers can also tolerate high levels of toxic substances such as cyanide.

Too Much Information

Gold-spotted mudskipper (Periophthalmus chrysospilos) Family Gobiidae

They tend to move around in groups, often in amusing 'herds', nervously moving just out of your reach. Sometimes they move in a line, following what seems to be the leader.

To about 12cm. Gaily speckled with orange spots on the undersides. The male raises his bright orange-and-black dorsal fin to court females and intimidate rival males. It eats small crabs, prawns and insects.

Giant mudskipper (Periophthalmodon schlosseri) Family Gobiidae

To about 27cm long, it is the largest of our mudskippers. It has a black stripe along the side of its body.

It builds a pool in with deep tunnels in the mud as a nursery for its young. At low tide, they are often in or near their pool. At high tide, they might be seen clinging to mangrove tree roots.

An aggressive hunter, it eats mainly prawns, small crabs and insects. It may even snack on smaller mudskippers!

Yellow-spotted mudskippers (Periophthalmus walailake) Family Gobiidae

To about 13cm long, it has a greyish body with scattered yellowish spots. There are brownish spots on the upper body. The first dorsal fin is reddish with a broad black band and narrow white margin.

It was previously confused for the juveniles of the Giant mudskipper (Periophthalmodon schlosseri). Unlike the Giant mudskipper, the Yellow-spotted mudskipper does not have a broad black band along the body length.

It is said to be nocturnal, leaving its burrow at night to forage and returning to the burrow in the morning.

Assorted smaller mudskippers

We can't really be sure what they are, especially if they are viewed from the boardwalk. They could be juveniles of larger mudskippers or different species of small mudskippers.

Mudskippers are probably the only fish with movable eyelids!
To keep their eyes moist when they are on land, the eyes can be retracted to dip them into water that collects at the bottom of the eye socket. Their retinas have rod receptors above and cones below, giving them colour vision above and monochrome vision below!

They can absorb gaseous oxygen through blood-rich membranes at the back of the mouth and throat and they also absorb air through their skin which is rich with blood capillaries, so long as the skin remains moist.

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