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Fish Out of Water
| Article
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11959 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
8 / 1987 |
892 Words |
| Author
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Lorus J. and Margery Milne
Lorus J. and Margery Milne are naturalists on the faculty of
the University System of New Hampshire, and authors of more
than 50 books on creatures they have observed around the world. |
As the tide ebbs, they appear by the dozens along the retreating edge of the water. They raise their eyes into the air, then crawl or flip themselves onto the wet mud. Others emerge in minor eruptions of liquid mud from burrows where they have taken shelter throughout the hours of high tide. These scenes could occur on any excursion into the Mai Po Marshes at the northwest corner of Hong Kong, where strange fish seem more at home in the air than in water.
Commonly known as mudskippers, their scientific name, Periophthalmus, refers to their ability to see in all directions with their protruding eyes. They are extraordinary members of the goby family of small tropical fishes. Well suited to an extreme range of habitats, their adaptive figures include two dorsal fins and ventral fins, more or less united. A tapering tail provides the flipping, but the crawling is dependent on front fins with muscular stalks that give an effective imitation of forelegs. Some use their ventral fins as a kind of suction cup or clasper with which to cling to a vertical surface, such as a mangrove root, while watching for food or a mate. The dorsal fins differ in color pattern and development from one species to another, and are flicked up like flags on display or lowered flush with the back, like a signal system to others of the same species.
Generally six to eight inches long, mudskippers belong to a mudflat community where salt and fresh water meet. Thirteen different kinds occupy these habitats from Burma to the China Coast, Japan, and northwestern Australia. All have a body that tapers backward from a massive head, and a low crosswise mouth with thin lips beneath a pair of nostrils. In all situations, the fish raises its eyes close together, moving them constantly to keep independent watch on the surroundings. At intervals a mudskipper blinks, bulging its eyes into its mouth much as a frog or toad might do, renewing the moisture that keeps them well wetted.
All of these popeyed fish favor places where mangroves are extending the shoreline and rooting in the soft mud. Most of these areas host three different species of mud-skippers, which spend different periods out of water. Those living closest to the high tide line get the most time in air, and dig deep burrows to reach a continuous supply of water. Those mudskippers near the low-water mark have least time in air and dig no burrows at all. Mudskippers of the middle range grow largest as herbivores that glean algae and other microscopic plants from the surface of the mud. The other mudskippers use the low tide hours by day to prey on small crabs and any insects that settle far from
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