Cold-blooded isn't an epithet, it's a way of life.
©1994 Melissa Kaplan
Well, you're not alone. Most of us past the dreaded age of thirtysomething start noticing the creaking and such that comes with aging. But is aging a process, or a disease? Research gerontologists are now beginning to ask--and research-- that very question. "The pathological changes we think of as aging are also pathological changes we think of as disease," says Huber Warner of the National Institute on Aging (NIA) in Bethesda, Maryland. Identifying just what aging is the primary question these researchers are asking, and their hunt for the answers is showing them some pretty wild stuff.
While we tend to think of all living organisms as having a finite life span, it appears that, at least with some life forms, that is not necessarily the case.
With mayflies, life is just a brief fling. Born without mouthparts (which would be completely unnecessary as they are also born without a stomach), the mayflies' brief three hours of life is solely directed towards finding a mate and procreating. (The house fly, on the other hand, can live for six months.)
Other invertebrates in the insect world are similarly short-lived. There is, however, one invertebrate that has thus far outlived any non-plant organism: the arctic clam, one of which is 220 years old.
Interestingly enough, the next two oldest non-plant organisms also happen to be cold-blooded. Over 150 years old when they died, a Mauritius tortoise and a sturgeon have both shown that, when left alone, many of these animals can live to very old age.
In fact, according to Whitfield Gibbons, a turtle expert at the University of Georgia's Savannah River Ecology Laboratory in South Carolina, turtles don't deteriorate--age--at all once they have reached their adult size. They cruise through life, swimming, eating and breeding until something or someone kills them. Taken into captivity when it was full grown in 1768, the Mauritius tortoise died when it fell through a gun port while strolling around the fort.
And so scientists search through tissues and enzymes and hunt for clues. Thus far it seems that the cold-blooded creatures are more likely to live longer (like those houseflies that spent the winter in some cold corner of your house, appearing as if by magic in the spring in your kitchen window), and those that consume less oxygen fare better than those who require greater amounts of oxygen.
While it appears that the large outlive the small, that is not entirely true: cats generally outlive dogs (especially the giant canine breeds), birds outlive rodents of the same size, and then, of course, there is the salmon. After it has made a Herculean effort to return to the pond in which it hatched, Mother Nature hits the death switch. The salmon don't die from exhaustion but from a host of problems related to long-term stress: ulcers, trashed immune systems, infections--all apparently triggered by the onslaught of the adrenal hormones which triggered the spawning trip.
Why do some animals die shortly after reproducing while others live on and on? Take a look at the natural history of some of these animals. The prime directive by which organisms function is to reproduce, sending the genes forward into succeeding generations. If the mayfly or the salmon were to live, they would end up competing with their own offspring for limited food sources. (That tiny mayfly, you ask? They die in such numbers that in some areas, snowplows must be used to move the mounds of dead flies.) The adult salmon (who cannot even eat fresh water foods) do not help raise their young, and in their depleted state would have to consume great quantities of food to be able to make it back to the ocean. Thus, once they have fulfilled their purpose--genetic reproduction--they die. Indirectly, I suppose, an argument can be made for their supporting their young, as their bodies are consumed by a number of organisms, many of whom end up being food for the salmon fry.
Turtles and tortoises also operate under the same directive--they live until they can no longer reproduce. And since once they reach sexual maturity, they never stop being able to reproduce, they live on and on. In fact, the older they get, the more eggs they lay and more of their genes are sent forth.
So why do humans and other primates live longer than the years in which they can reproduce? Humans, ranging in life span somewhere between the mayfly and the turtle (oldest authenticated human was 120 at the time of death), are primarily social animals, and the older nonreproductive members of the social unit share their survival experience with the unit's offspring. As some of their genes are in every crop of offspring, it is to their benefit to care for all the young, thus ensuring the survival of their genes. This shared caring for and training of youngsters can also be seen in other socially oriented mammalian species such as the wolves.
Given the fact that cold-blooded animals live so long (the oldest bullfrog died at 16), we have to ask ourselves why so many die so young when they are in captivity. Let's look at this question from another direction. The human life span used to be shorter. In time, as diets improved, more food resources were produced and the art of medicine gradually evolved into a science, humans began to live longer. Why, given all of our technology, are we not experiencing full productive lives into the 90's or beyond? The products of our toils have led to increases in cancers, stress-related diseases, pathogens which rob the body of its regenerative powers, and diets bearing little resemblance to what early humans consumed.
The answer to the above question is painfully clear. When we fail to provide a safe environment and proper nutrition, and fail to treat medical problems resulting from these stresses and other factors of captivity, we commit murder by a sort of passive euthanasia. Because of the cold-bloodedness and slowed metabolisms, it may take a year or two, or more, to finally die. And that is why many serious herpetoculturists will lecture and pound on those people who do not care properly for their animals.
There is so much out there that we still know so little or nothing about. Many of us often forget that humans are just one of millions of species. Whether we choose to share our homes with other organisms or whether we prefer them out in their natural environment, we must be ever mindful of their needs, providing what they require and making sure that the wild ones continue to have a place to live and fulfill their genetic destiny...or just so that we know that they are out there. It was either Farley Mowat or Edward Abbey who said that it was not because he had any great desire to see a grizzly bear in the wild that he wanted to preserve grizzlies and their habitat, it was just knowing that they would be there if he ever wanted to. I know I will never live to see a tiny fraction of life on earth...but I feel better knowing that they are out there for others to know about and maybe lucky enough to see.
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© 1994-2013 Melissa Kaplan or as otherwise noted by other authors of articles on this site