What are Mud Skipper
If you have anytime visited the tidal mudflats in the Sundarbans, i.e. wetland in the coastal areas where mud is deposited by tides or flowing rivers, must have noticed some fishes which are crawling on the mud. It looks as if the fishes are 'walking'. They are also seen climbing the roots of mangrove or salt tolerant trees which are also known as halophytes. These fishes, known as mud skippers, are common on tidal mudflats throughout tropical Africa, Asia and Australasia where they crawl out of water. They feed on algae, small invertebrate animals, particularly small crabs, insects and fish larvae, etc. Mud skippers are common in the seaward edge of the mangroves which part is inundated daily. They also climb on the mangrove roots. Mud skippers are semi-terrestrial fishes belonging to the fish group commonly known as 'Gobioid' fishes. They build towers made up of mud around their burrows. These fishes have strong pectoral fins i.e. fins in the shoulder region which are well designed for movement out of water. Mud skippers are amphibious and can survive long periods out of water. Their mode of locomotion separates them from other fishes. Interestingly, the physiological studies have shown that the gills of mud skippers are better suited to atmospheric respiration than aquatic respiration.
Respiration and Locomotion
When a mud skipper leaves the water it closes its gill-flaps (opercula) and rapidly inflates the chamber behind the gills. This process traps oxygen and water to continue respiration on land. They have highly vascularised membranes at the back of the throat and mouth which are used for breathing atmospheric air. Mud skippers are also able to climb on mangrove roots. Although the mud skippers are adapted to terrestrial life yet they need periodically to go to water. The eyes are set high on the head, giving the fishes a peculiar, frog-like appearance. Mud skippers are highly territorial and mostly aggressive.
Variety of Mud Skippers
There are different types of mud skippers living in the Sundarbans. The scientific names of the species of mud skippers seen in the region are, Periophthalmus koelreuteri , Periophthalmus barbarous, Periophthalmus chrysospilos, Periophthalmus kalolo, Periophthalmus malaccensis, Periophthalmus pearsei, Periophthalmus vulgaris, Periophthalmus novemradiatus,Periophthalmodon septemradiatus, Periophthalmodon schlosseri, Boleophthalmus boddarti ,Boleophthalmus dussumieri, Boleophthalmus sculptus, etc.
The mud skippers are found in abundance in shallow burrows on the muddy banks between tidal marks in channels near the mangrove bush where the mud does not dry out even during long exposure to sunlight. I photographed a mud skipper near its burrow in Bakkhali which is shown in fig.1.The tidal mud flats provide suitable environment for colonization of the mud skippers and other mangrove-associated animals. The mud skippers prefer to remain hidden from sight and highly territorial. They feed both on plant materials and small invertebrates and live in community tubes in association with the tubes of polychaete worms and Red Crabs. As told earlier, the organs of aerial respiration are developed in connection with the buccal cavity and the gill-chambers, which have well developed pouches for storage for air and the gill-covers are specially modified to keep the openings tightly closed. The mangroves of Sundarbans provide very suitable habitat for numerous organisms that are adapted to live, reproduce, and spend their juvenile lives.
The other day I was watching the Discovery Channel in which it was shown about a fish which is easily walking on water and mud with style. I forgot the name of the fish. But from this article it is now clear that it is called Mud skippers and they can do those acrobatics with such ease. What I request the scientists fraternity is to save the species of these rare fishes which may not be seen in other places of earth. So there must be detailed survey on the number of species of this rare fishes and that should be documented.