Turkeys and Parthenogenesis

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.

A New Mexico Whiptail (Aspidoscelis neomexicana). All New Mexico Whiptails are female. The entire species reproduces by parthenogenesis.

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.

This diagram from the BBC actually explains shark parthenogenesis but you get the idea.

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.

Turkey Poults

Wild Turkey Poults

During February and March, tom turkeys beguile hens with their magnificent gobbles and vivid visual displays. Shortly thereafter the hens begin nesting. Not only are turkey eggs larger than chicken eggs, they are covered with delicate brown speckles and tend to have a more acute taper on one end than chicken eggs do.  The turkey hen constantly broods her eggs leaving only briefly to eat.  When she is sitting on her nest, the hen is extremely vulnerable to predators.

Turkey Eggs

A month later, turkey poults emerge from the eggs.  The tiny poults punch open the egg with egg teeth (sharpened ridges on the beak which quickly vanish as the young turkeys begin to grow). Wild turkey poults leave the nest about a day after they hatch.

Bourbon Red Turkey Poults on a farm

Wild turkeys face a terrifying host of predators including bobcats, raccoons, skunks, opossums, foxes, coyotes, armadillos, weasels, crows, owls, hawks, bald eagles, and a variety of snakes. To cope with this list wild poults quickly develop limited flight capability and begin roosting in trees two weeks after they hatch.  Domestic turkey poults need substantial warmth to thrive and must be kept under a hot lamp and never given cold water.  They need medicine supplements to prevent infection from chicken diseases and special calcium supplements to make up for the minerals which their wild cousins get from the bugs and arthropods which make up the bulk of their diet.

Day old Narragansett Turkey poults (photo by Cackle Hatchery)

One of the most endearing traits of poults is the way in which they imprint on their mother and then follow her around.  This trait is identical in domestic turkeys: when we ordered poults during my childhood, the little fluffy birds imprinted on me.  Thereafter they would follow me around the barnyard peeping–which was very cute but made me worry about their well-being (imprinting being a two-way street).  The young turkeys were affectionate and endlessly amusing.  Indeed the Aztec trickster god Tezcatlipoca was strongly associated with turkeys because of their playful tricks and the deity was said to sometimes manifest as a turkey.  In the picture below, Tezcatlipoca even looks a bit like a strutting Tom.

A Turkey and Tezcatlipoca. Do you see the ressemblance?