Millennium Post

Tracing characteristics of fish

Can the age of fishes be determined?
Scales, bones, fin rays and fish ear bones (otoliths) have all been used to determine the age of fish since these and other bony parts of fish often form yearly rings (annuli) like those of a tree. However, otoliths generally provide the most accurate ages, particularly in older fish.
Do all fish swim in a horizontal position?
Most do. The seahorse is among the exceptions. Another is the shrimp fish of the Indian Ocean, which congregates in schools of several individuals and swims vertically, its long tube-like snout pointing directly upward. A catfish indigenous to the Nile and other African rivers also swims in the vertical posture.
I have never seen fishes sleep. Do they?
The nature of fish "sleep" is an area of active research. While fish do not sleep in the same way that land mammals sleep, most fish do rest.
Research shows that fish may reduce their activity and metabolism while remaining alert to danger. Some fish float in place, some wedge themselves into a secure spot in the mud or coral, and some even locate a suitable nest. These periods of "suspended animation" may perform the same restorative functions as sleep does in people.
Yes, fish sleep. But it's not sleeping as we know it. They don't have eyelids to close, they sometimes do it during the day, they don't show the characteristic brainwave patterns like REM sleep seen in humans, and some, including most sharks, have to keep swimming in their sleep.
But fishes do have a period of reduced activity and metabolism which seems to perform the same restorative function as nocturnal sleep does in humans. Some are more obvious about it than others and actually rest on the bottom or in coral crevices, and parrotfish secrete a mucus "sleeping bag" around themselves before they go to sleep. If you get up quietly in the middle of the night, you will find your goldfish in an almost trance-like state, hovering near the bottom of the tank making just the minimum correcting motions with its fins to maintain its position in the water column.
Is there still any place in India where new species can be discovered?
Almost all of India's natural wildlife has not been discovered because we have very few scientists who have the ability and interest in exploring our natural wealth. We would much rather destroy forests than find out how we could benefit from its treasures. The Western Ghats is one example in which thousands of unknown creatures abound. In ten years from now, they will almost be over as Kerala wants to turn them all into housing colonies. But every week or so, some scientists find a new species. For instance, in March this year, the Division of Arachnology of Sacred Heart College, Kochi in India, under the leadership of Dr PA Sebastian, who have found many new kinds of spiders discovered yet another a little jumping spider with a unique whitish plug on the compulsory organ of the male spider which functions as the paternity protection devices.
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