We all learned back in school that it was Gregor Mendel who discovered the laws of genetics in the mid 19th century. Since that time the study of how living creatures pass on their characteristics to their offspring has uncovered more than a few strange and wondrous facts of nature.
There have been two recent studies published that caught my eye because they both showed again just how strange and miraculous living things can be. The first study deals with a newly discovered species that reproduces naturally by cloning while the second species seems to have found a way to live without actually aging.
The first species is known as a marbled crawfish, a species that is becoming a very common animal in the streams and ponds of Europe. The crawfish is also widely kept in the aquariums of people who maintain fish as a hobby, a few of you out there may have one or more in your tank. See the image below.
In fact it was these hobbyists who first brought the crawfish, also known as a marmorkreb which is German for marbled crawfish, to the attention of geneticists when it appeared that their pets were reproducing without ever having mated, and the offspring were all female. The crawfish it seems were laying already fertilized eggs, in other words they were cloning themselves.
For the past five years now biologist Frank Lyko of the German cancer research center has been unraveling the genome of the marmorkreb and has found some amazing results. Probably the strangest thing that the scientists found was that the crawfish possessed triplets of chromosomes instead on pairs as in most creatures, technically this makes the marbled crawfish a triploid. Think about that, we humans have 23 pairs of chromosomes and in each of those pairs we got one chromosome from our mother and one from our father.
Normal crawfish have pairs of chromosomes like other animals but the marmorkreb crawfish is a triploid and the eggs laid by the marmorkreb are also triploids and are therefore already fertilized. Dr. Lyko isn’t certain how the crawfish manage to live with all of that extra DNA but they certainly do live. In many areas of Europe the crawfish are becoming a nuisance, pushing out their more normal relatives.
Dr. Lyko also believes that the marmorkreb crawfish is not just a newly discovered species but an actual new species, one that is perhaps as little as 25 years old. Dr. Lyko speculates that a single mutation, perhaps in someone’s home aquarium, gave birth to this new species.
Now before you start thinking that the marmorkreb crawfish is the weirdest thing you’ve ever heard of I should point out that scientists do know of other species that reproduce by cloning as well as species that are triploid in their chromosomes. In some ways cloning is a big disadvantage however since all the members of a species are identical any disease that can kill one of them can also kill all of them. For this reason biologists think that cloning species do not survive for very long. Another example of how diversity is a measure of the health of a species.
Our second unusual species is known as the naked mole rat and it is perhaps best known as one of the ugliest animals alive, see image below.
Scientists have known for a long time that naked mole rats are quite different from other rodents. Living almost their entire lives underground they have evolved to obviously be almost hairless as well as nearly blind. Naked mole rats were also known to be virtually cold-blooded like a reptile.
Now scientists at Calico Life Sciences LLC have found considerable evidence that naked mole rats do not physically age. Specifically they assert that naked mole rats do not obey Gompertz’s law of mortality.
Now Gompertz’s law of mortality is just a specific statement of something everybody recognizes. The older you are the more likely you are to die by natural causes in the near future. In other words an 80 year old person is more likely to die in the next year than a 60 year old, a 60 year old is more likely to die than a 40 year old and so on.
Every other known species of mammal obeys Gompertz’s law, even other rodents. The common brown rat for example has a much greater chance of dying by natural causes at age five, that’s old for a rat, than it did at age four.
Naked mole rats live on the other hand are known to live past 35 years of age, that’s very old for a rodent, and the researchers at Calico Life Sciences have been keeping a careful track of 3,000 data points of the mortality of mole rats versus their age and their conclusions are that a 30 year old mole rat is no more likely to die by natural causes than a 20 year old or even a 10 year old.
Naked mole rats also show many other signs indicating that they do not physically age. They rarely get cancer, their hearts and bones do not weaken with age and they never go into menopause.
Obviously scientists would like to know what is in the naked mole rats DNA that gives them these peculiar characteristics. As for the rest of us, maybe from now on instead of insulting mole rats for their appearance we might want to envy them, at least a little.