Dr. Bortrum
08/07/2008
Another Odd Animal
E = mc2! You already are familiar with this equation I’m sure, so why the exclamation point? I’ve been writing this column for over nine years and you can’t imagine how frustrating it has been for a scientist not to be able to use superscripts or subscripts due to the limitations of the stocksandnews.com Web site software. But now, with the new Web site software, I can write H2O as it should be written, H2O. Halleluiah! I can even write 10-4 instead of 0.0001 or 1010 instead of 10000000000 or 10^10. Oh, perhaps I should mention that the reason for me not posting a column last week was that our editor Brian Trumbore wasn’t sure 80-year-old Bortrum could handle the mechanics of posting in the new environment, which made its debut here last week.
In my last column of two weeks ago, I promised to discuss the platypus, continuing the theme of strange animals such as the sponge. However, I would be remiss if I didn’t continue my Phoenix watch after the big news from Mars this past week. You’ve no doubt learned from the media that Phoenix succeeded in scooping some of the presumed water ice from under the surface of Mars into an oven and, sure enough, after all these years, it’s definite. There is water on Mars. As NASA put it, they’ve finally “tasted” the water there.
But Phoenix had company in the quest for water. The Messenger spacecraft launched to study Mercury, closest to our Sun of all our solar system planets, has found water fragments in the atmosphere around that planet. In 11 papers in a recent issue of Science, the Messenger team reports on the first findings of the Messenger mission. How come there’s water so close to the Sun? One possibility suggested some years ago is that shaded craters of Mercury might actually be cool enough to harbor water ice. Other possibilities are that the solar wind is reacting with Mercury’s surface to form water ions or that small meteorites bearing water are banging into Mercury. If I had to bet, I’d probably go with one or both of the latter two possibilities.
Another NASA orbiter, Cassini, is still circling Saturn’s moon Titan and has now confirmed the presence of lakes on Titan. One, they’ve named it Ontario Lacus, is as big as Lake Ontario here on Earth. This lake doesn’t contain water but consists of liquid methane, liquid ethane, liquid nitrogen and various organic compounds. It’s doubtful future space travelers will want to spend their summer vacations swimming in these lakes.
The platypus can be found swimming in the waters of Australia and Tasmania. If the sponge is one of the simplest and primitive of multi-celled animals, the platypus has to be one of the most unlikely. Classified as a mammal, it does fit the definition of a mammal as being an animal species in which the young are fed milk produced in the female mammary glands. However, the platypus lays eggs, has a bill like a duck, a tail like a beaver, webbed feet and the male has a claw that connects to a venom-producing gland. Like a snake, the male uses the venom to dispatch its enemies. The female uses its claws to dig a tunnel in the bank of a stream and build a nest, like a bird, in which it deposits typically one to three eggs with thin shells like those of a snake or a turtle. When the young hatch the mother clasps them to her with her tail to nurse; the young stay in the nest for several months.
All this is well known to platypus enthusiasts. So what’s new? Brian Trumbore called my attention to articles by Helen Briggs on BBC News and by Rick Weiss in the Washington Post date May 7 and May 8, respectively. The articles refer to work published in the journal Nature by an international team of scores of researchers that has decoded the platypus genome. When British scientists received a specimen of the platypus from Australia, one can hardly blame them for thinking it might be a hoax. With such a strange mix of characteristics, it would not be surprising if the genome of this odd animal is itself rather odd. It is.
The genome is a mix of genes avian, reptilian and mammalian in nature. It’s as though the platypus got stuck in a time warp in its development when it wasn’t sure what it was slated to become. Take the venom, for example. The platypus is the only mammal that produces venom but the genome work shows that the platypus developed its venom independently from the reptilian version in the snake. Yet the chemical compositions of the two venoms are surprisingly close to being identical.
Then there’s the sex problem. Most mammals, including us humans, have two sex chromosomes. Being a male, I have an “X” and a “Y” chromosome. My wife has two “X” chromosomes. The platypus has 10 sex chromosomes, which are closer to the “Z” and “W” chromosomes in birds. Furthermore, the gene that is most influential in determining maleness in the “Y” chromosome is missing from any of the 10 platypus sex chromosomes. Yet that gene is found on another chromosome having nothing to do with sex!
Then there’s the egg laying and the birdlike behavior. The chicken has three genes for one of the proteins in the yolk of the egg while the platypus has only one. It’s as though the platypus is heading towards the emphasis on more nourishment of the young after hatching than before hatching. In his article, Rick Weiss quotes Ogden Nash as being credible in his view of platypus child rearing: “I like the way it raises its family/Partly birdly, partly mammaly.”
Another intriguing feature of the platypus is the fact that it’s apparently blessed with keen eyesight, yet when underwater, it closes its eyes and relies on touch and another sense that allows them to detect changes in electric fields generated by their prey. The researchers don’t seem to have found the genes associated with this “electroreception”, so to speak. The genes they have found, however, should be invaluable in elucidating how this outlandish creature and other “normal” creatures have evolved over millions of years.
Well now to posting this column. If you’re reading this, you’ll know that I’ve mastered the new system or that Brian Trumbore has stepped in to post it. Oh, thanks to Charles K, who sent me an e-mail with a cute little image of a platypus in anticipation of my fulfilling my promise to write about the critter this week.
Allen F. Bortrum
