Writing about things that I care about provides enjoyment, satisfaction, and a degree of comfort similar to that which the consumption of chocolate provides to others. Today was a difficult day, for reasons that I cannot determine and so, for the pleasure of it, I return to one of my favorite topics, one which I have discussed here before, the perpetuation of the species and the transmission of genetic material. My desire to write about genes may also have been influenced by a fascinating paper I read recently in which scientists described a new technique which allows for the visualization of bundles of DNA fibers using the methods of traditional transmission electron microscopy. The last time I mentioned DNA here it was in reference to the seeds of the milkweed plant. This time my story begins with a walk that Joanna and her good friend, Ann, enjoyed the other day. When she returned I asked Did you see any nature? She was excited to tell me about masses of frog spawn she had seen; a sure sign of spring. A few days later we took our bike along the same stretch of trail and came across a group of folks from the Department of Natural Resources and from a local fire department. The combined forces had just completed a controlled burn parallel to and just off the walking path. For days Joanna worried about the fate of the eggs. She fretted, not only because of the fire but also because the egg masses had been deposited in a small depression which ran along side the trail and her concern was that the water might have dried in the intervening days which had not seen much rain. This past weekend we had the bike out once more and stopped to observe the spawn. All was well. The encapsulated embryos were housed as part of jellied, buoyant, masses and glints of sunlight danced across their surfaces. The embryos were of such interest that I decided to post this trio of images. Each embryo floated, in its tiny, protective, capsule. Quiet, save the periodic paroxysms which moved it about its watery abode. Each embryo grew under the influence of DNA molecules deep within each of its cells. How strange, as if the entire scenario were taken from a script of some Sci-Fi movie. Eventually the embryos would complete organogenesis, hatch as tadpoles, and then undergo metamorphosis to the adult stage which is perhaps more familiar to us. It is a fascination to contemplate the motive forces which drive these processes and the motivation for them. My best explanation of the former relies on the laws of thermodynamics. In the same way that, having attained the top of that very first hill, a roller coaster car transforms the energy of potential into the energy of movement, chemicals too interact and thereby achieve low energy states. The DNAs, the RNAs, the polymerases, the helicases, and the topoisomerases all interact in ways which eventuate as a collection of proteins we call frog tissue. In other words, organogenesis and development are, in my view, fortuitous side-consequences of the entropic interplay between and among abiotic (nonliving) molecules. And, it’s totally, entirely, and absolutely without conscious motivation or foresight. For who could assign motive to interacting chemicals anyway? Chemical moieties react with chemical moieties because the laws of thermodynamics dictate they will. What a weird and wonderful thing it is to view a frog as a not-so-simple side consequence of DNAs competing, thermodynamically-speaking, in a world of other DNAs, and doing so because they can. As for motivation? There isn’t any. How could there be? Isn’t it grand?
It’s a week today that our lambing season began. As of this afternoon we have lambed 29 (and lost three) out of 20 ewes. Our current numbers include 8 sets of twins and 10 singles. Among the little ones are 11 pure shetlands (7 rams and 4 ewes) and 15 crossbred animals (5 rams and 10 ewes). Woodruff, our established flock sire, settled 17 ewes and Siegfried, heir apparent, settled 3. There are still 3 ewes that have yet to lamb. It was sunny today and many of the little ones tagged along as their mothers grazed, hydrated, and recovered. Being little requires a tremendous amount of work and, like all newborns, the lambs spend much of their time sleeping. Sometimes a ewe will wander off, unaware that her charge has flagged. When the lamb wakes to find its mother gone its reaction is immediate. It’ll call as loud as its lungs will allow and run, frantically, first in one direction, and then in another, and then in another, calling all the while. The very moment it sees its mother it’s off like a shot for a drink and for a bit of reassurance. The lambs are quite sociable and eager to play, even when only a day or two old. Small groups will gather and run … for no apparent reason other than that they can. Just a few moments ago Joanna and I came in from evening chores which, during lambing season, includes a final check to see that all the lambs have an ear tag. If we come upon one without a tag it means we’ve had a new arrival. We also check to see that all is well. This evening, just a few minutes before the sun settled below the horizon, the lambs were zooming back and forth with their mothers in hot pursuit. It seems the call to bed time had been issued. Joanna swears she could hear the mothers calling … if you don’t get back into bed there’s going to be trouble, and I’m not going to ask again!
Ram lamb #1420 arrived yesterday, along with sister, before the sun. I was up at four, loaded wood into the cook-stove and was in the truck by quarter past. Just as I was about to heave the door I heard a ewe call, I paused for a moment. I heard her again, and then a lamb. And then the ewe. And then the lamb. I started the truck and turned the head lights on, they cast light out into the pasture and between two sheds. I pulled the truck forward and to the left a bit such that light shined into the bigger shed to the south. Sure enough there were two sets of tiny eyeballs, blinking in the brightness. This particular shed is quite large and is divided in the middle by a supporting wall. As I squinted into the illuminated bays I could see that one newborn was on one side of the wall and the other was on the other side. The ewe was beside herself, running from bay-to-bay, and fretting at the calls of her babies, one always out of sight. Either she had delivered the two on opposite sides or somehow one of her little ones had wandered in the darkness. What would you have done? I was wearing my good school shoes, already behind schedule, and didn’t want to take the time to run back to the house to change into my barn boots. I kept the truck running, made my way through the barn, into the pasture, and then out to the shed. It took just a second to catch up little #1419 and to unite her with her brother. June was delighted and could now concentrate on the business at hand, and in one place. I jumped back into the truck, heaved the door, and pulled it in gear. The day was bright and sunny. With afternoon chores behind me I took up the D600 and went out to take some lamb portraits. Here’s June and #1420, neither seemed any worse for wear for having been involved in a bit of predawn confusion.
Given the way in which blogs are presented, I am convinced that posts which reside more than a scroll or two behind the most recent are doomed to languish and to be forgotten. Because I believe there is value in looking at contributions from days, weeks, and even months ago, I present here a gallery of images presented during March of 2013. Perhaps it will be interesting to scroll through these and to compare them to those presented during this past month. Be patient, it may take several minutes for all of the images to load fully. Hovering over an image will reveal its title. Clicking one will take you to a carousel view and you can either move through the collection or click the links to read each post in its original form. Note that this is the thirteenth in my series of retrospective posts. If you’d missed any of the others you can find them all by using the search feature in the sidebar to the right, simply search for retrospective.
If you can identify the object below please ignore the fact for just a moment and tell me what the image reminds you of. It looks to me like a leaf, complete with midrib and lots of ramifying veins. The dark nodules remind me of the sort of damage produced by certain aphid infestations. In fact, this is a photo of part of a sheep placenta delivered here the other day. The mammalian placenta is a fascinating structure and one which I have discussed before. Joanna agrees that the placenta is remarkable but wonders how an image of one will be received by those who frequent this blog. Mammals are classified as either monotremes, marsupials, or placentals and differ in the way in which they house and nourish their developing embryos. Monotremes such as the platypus have retained the egg-laying habit of their avian and reptilian ancestors, marsupials develop for a brief time within the uterus and complete their growth in an external pouch, and placental embryos develop within the uterus and are nourished by a remarkable structure called the placenta, the physical and chemical link between a mother and her developing offspring. The intent of this post is not to teach anatomy and physiology but to stop to appreciate this remarkable structure. The image reveals the delicate membranes and blood supply so important in sustaining fetal life. The four nodules are cotyledons. Remember that a developing fetus is connected, via the umbilical cord, to the placenta. How the circulation of the placenta communicates and interdigitates with that of the mother is amazing. Suffice it to say that the two blood supplies do not mix (it is a popular misconception that they do) but are separated by the thinnest of protoplasmic layers. This syncytial trophoblast may be thought of as a single cell covering the entire placenta. The two blood supplies flow past one another so closely that material exchange may occur via diffusion and by active transport. Oxygen and all of the nutrients required of the developing fetus are supplied to and across the placenta and wastes such as carbon dioxide and urea are removed via the same route, but in the opposite direction. To increase the surface area for exchange, placental capillaries ramify and spread into twenty or more structures, the cotyledons, which then communicate with the maternal blood flow. Often I find myself admitting to my students that this sort of stuff is just crazy fascinating and crazy elegant. What do you think?
So, yeah, I made a big deal about expecting lambs in the middle of March; Mea culpa, but not entirely. Let me explain. First off I will admit that although I failed to note the day we put the ewes out with the rams, I was fairly certain that that had occurred on or around October 15. Ovine gestation lasts about 150 days so I was not surprised when we did not have lambs on March 1 but was quite perplexed when the season did not begin, two weeks later, around the middle of the month. Day after day went by and the Joanna began to ask … Are you sure they’re bred and you haven’t just been feeding them too much? I assured her that the ewes had been with the rams for long enough for two complete heat cycles. When April 1 rolled around I began to worry and wondered whether we should catch up the girls to check to see if any was ‘bagging up.’ And then I thought, if the ewes had been cycling synchronously and had been first exposed to the rams just as they were coming off a cycle on October 15, that would have put lambing off another 17-21 days … just about right for #1407 (a little boy) to have arrived this afternoon, between rain showers. So you see, there’s always a rational explanation. Next year I will watch the ewes closely for signs of heat around the time they are first exposed to the rams and promise to note the date of first exposure on the kitchen calendar.
I don’t believe this post requires explanation other than to say a small handful of Joanna’s Crocus made a much anticipated appearance yesterday amid blue sky and mild temperatures. Although bare ground remains, the number of vigorous green shoots is evidence enough to assure me that the season is moving in the right direction. Now, if only the lambs would get with the program.