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The winter is gradually passing away into spring–which should be an exultant season for flower gardeners. Yet the results in my back yard are extremely discouraging because the ferocious squirrels of Brooklyn have eaten all of my crocuses! Despite planting an immense number of the hardy little flowers, I am still bereft of spring color. I guess I should have expected something like this after the infernal bushy-tailed rodents ate all the glass bulbs from the Christmas lights…
As it turns out, squirrels are not the only ones who love crocus flavor. One of the world’s most precious spices is made from the little flowers. The gourmet spice saffron literally consists of the harvested stigmas of the saffron crocus (Crocus sativus). The saffron crocus plant has been domesticated since antiquity to provide the costly spice and the plant literally owes its existence to human appetite for the powdery threads. Crocus sativus is a descendant of Crocus cartwrightianus, a wild crocus from the rocky skree of southwest Asia. As humankind selectively planted the plants with the longest stigmas (and hence the most delicious saffron) the little crocus developed into a completely different—and completely dependent—species. Crocus sativus now has magnificent spiraling stigma covered in deep yellow pollen, but the artificial selection came at a terrible cost. The plant is a male sterile triploid, incapable of sexual reproduction thanks to its extra chromosome. Saffron crocuses can only reproduce asexually and they require human assistance to prosper. The spice is still prohibitively expensive since the little plants must be planted and harvested by hand.
Saffron is known to recorded history as early as the 7th century BC (when it was mentioned in a Assyrian botanical treatise) however archeological and genetic evidence suggest that saffron has been harvested for at least 4 millenia! Since saffron contains over 150 volatile and aroma-yielding compounds, I am not going to try to describe it to you—you’ll just have to get some yourself. My favorite dish which uses the yellow pollen is mussels, saffron, vermouth, and cream!
Of course I am cheating a little bit by writing this article in the spring–the saffron crocus is really an autumn flowering plant. However I felt like my slaughtered crocuses deserved some sort of memorial tribute. Of course if I really wanted to commemorate the slain flowers I could turn to my paint box. In addition to being a spice, saffron is also a color—a deep orangey gold reminiscent of foods prepared with the spice. Strangely, for a color so steeped in the sensory joys of living, saffron has also come to represent worldly renunciation. Buddhist monks wear robes of deep saffron and the top bar of the Indian flag is the same rich orange-yellow. The flag’s designers hoped that the color would inspire India’s leaders to set aside material gains and dedicate themselves to the welfare of the people, but, alas, in all societies such selfless dedication is even rarer than the rarest spice.
Regular readers know how much I esteem turkeys. Unfortunately I worry that my writings are not winning additional admirers for these astonishing birds. It is time to play a trump card and reveal one of the great bizarre strengths of turkeys. They are capable of virgin birth.
Before you spring up in alarm and start shouting, allow me to present a miniature biology lesson. Parthenogenesis is a form of asexual reproduction. Some female organisms are capable of producing an ovum which develops into a new individual without being fertilized by a male gamete. In these cases, the mother contributes her genetic material to the offspring. Although natural parthenogenesis is frequently observed in rotifers, insects, mollusks, crustaceans, and flatworms, this method of reproduction is much less common among vertebrates. However a few species of fish, amphibians, and reptiles are known to reproduce via parthenogenesis (movie-goers may recall that this happened to the dinosaurs in Jurassic Park.) The turkey is very unusual in being a bird which can reproduce through this means (or at least we think it is unusual—perhaps parthenogenesis is more common among birds then we realize but we just don’t know about it except in settings like farms where it becomes obvious). Chickens can also produce self-fertilized eggs but they almost never develop beyond embryonic stages, whereas female turkeys can and frequently do produce living offspring which lack fathers.
Parthenogenesis occurs in turkeys through the doubling of haploid cells. Biologists have discovered that the rate at which this occurs can be increased by selective breeding. Poults produced by parthenogenesis are capable of growing into healthy viable toms indistinguishable from toms with more traditional parentage. You will note that I wrote “toms”—all turkeys conceived via parthenogenesis were created from doubled haploids and are are homogametic. Consequently they are all all male. (This will leave mammal enthusiasts scratching their heads–since female mammals are homogametic and have two x chromosomes. However for birds and for some reptiles, males have two Z chromosomes and thus are the homogametic sex. In such species, females have one Z and one W chromosome and are the heterogametic sex.)
Mammals do not naturally utilize parthenogenesis as a method of reproduction. Certain portions of mammalian genes consist of imprinted regions where portions of genetic data from one parent or the other are inactivated. Mammals born of parthenogenesis must therefore overcome the developmental abnormalities caused by having two sets of maternally imprinted genes. In normal circumstances this is impossible and embryos created by parthenogenesis are spontaneously rejected from the womb. Biology researchers have now found ways to surmount such obstacles and a fatherless female mouse was successfully created in Tokyo in 2004. With genetic tinkering, human parthenogenesis is also biologically feasible. Before his research was discredited and he was dismissed from his position, the South Korean (mad?) scientist Hwang Woo-Suk unknowingly created human embryos via parthenogenesis. To quote a news article by Chris Williams, “In the course of research, which culminated with false claims that stem cells had been extracted from a cloned human embryo, Hwang’s team succeeded in extracting cells from eggs that had undergone parthenogenesis… The ability to extract embryonic stem cells produced by parthenogenesis means they will be genetically identical to the egg donor. The upshot is a supply of therapeutic cells for women which won’t be rejected by their immune system, without the need for cloning.”
All of which is fascinating to biology researchers (and those who would seek greatly prolonged life via biogenetic technologies), however it seems that in nature, the turkey is the most complicated creature capable of virgin birth.