Life on Other Planets from a Biological Perspective: The Lungfish
About the biological perspective of life on other planets taking into account the forms life takes, consider the unusual lungfish.
Life on Other Planets: Another View
The African lungfish (Protopterus annectans) is known to be able to survive for 4 years out of water, in a state of profound anabiosis. Dr. Homer W. Smith, chairman of the Dept. of Physiology at the New York University School of Medicine, estimates that "if the animal has a maximal store of fat when it goes into estivation, and if it gets the breaks from nature . . . it might survive for 7 years."
When the lungfish finds itself without water, it burrows into the drying mud and secretes around its body a mucous cocoon that hardens into a tough, leathery wrapping. Virtually mummified, it breathes air through a small hole running to the surface. According to Dr. Earl S. Herald, curator of aquatic biology at the Steinhart Aquarium, San Francisco, the lungfish does not use fat, as do other animals, in estivation or hibernation. Instead, Herald says, it absorbs its own muscle tissue!
Except for the oxygen brought in from the outside world, the lungfish thus lives in an environment of its own construction, a nearly closed system (not unlike the closed-system spacecraft engineers and scientists are struggling to design). As its metabolism slows to a niggardly rate, the lungfish lives on itself. Tests have shown that lungfish in cocoons for a mere 6 months have dropped in weight from 13.2 ounces to 10.2 ounces and length from 16" to 14 3/8". Most vertebrates, especially man, cannot tolerate much urea; the presence of as little as 10 parts per million of this toxic waste product in a vertebrate's system is usually fatal. But the incredible lungfish's equally incredible kidney separates the urea from the water in its body over and over again. The concentration of urea builds up more and more--it has been known to go as high as 20,000 parts per million.
What keeps the lungfish alive for years in its waterless, foodless, sunless crypt? The answer seems to be a fantastic ability to conserve energy, to squeeze the last drop out of the stuff of life--to force life to feed upon life, to slow down time. Motionless, barely alive, a stinking, self-made sewer, the lungfish is nonetheless as wondrous as Keats's Grecian urn, for this thing from the dry earth is also a "foster-child of Silence and slow Time."
Eventually, the lungfish will be released from its crypt. Freshening water will come again, and it will swim once more. But there are other creatures whose entire lives are spent in environments that a student of extraterrestrial life might well call unearthly. For example, it was assumed that life could not endure the extremes of the abyssal depths of the sea--utter darkness, near-freezing temperatures, and pressure of more than 1,000 tons per sq. ft.
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