A Boa Constrictor female snake has become a new mother—in what’s dubbed a "virgin birth" resulting in 22 all-female babies with no dad, each baby a half-clone of the female boa, the mom's eggs fusing with themselves.
The “virgin birth” discovery now adds boa constrictors to a list of animals that can actually give “fatherless” birth. So far that potentially fatherless list includes other snake species, three shark species, the Komodo dragon and some monitor lizards, certain termites—and a few others.
Maybe more surprising is that research now shows some dinosaurs may have given “virgin birth”—an unusual phenomenon now reported in all lineages of jawed vertebrates except mammals, and a number of invertebrates. Molecular tools are showing that the “virgin birth” is more common than science previously thought.
The mother boa constrictor gave birth twice, to a total of 22 caramel-colored females—odd, since the male snakes who were housed with the female boa did not carry the gene for the recessive color trait shown in the babies. Scientists extracted and analyzed DNA the mother boa’s shed skins, from the males and the new caramel-colored babies. The DNA test—which functions similarly to a paternity test—showed a sex chromosomal arrangement of WW for the newborns.
The male boa snakes have the sex chromosomal arrangement ZZ, and females ZW. Previous studies had concluded that the WW chromosomal arrangement pairing was not viable—but the baby boas have shown that to be untrue.
Scientists believe the recent boa constrictor births are due to “Automatic Parthenogenesis”. In Automatic Parthenogenesis , the babies receive one set of the mother’s chromosomes as they split during egg production, but lack sperm to create the complementary set of chromosomes, so the egg instead fuses with itself in beginning development of the embryo.
The mother boa constrictor responsible for producing the new litters of 22 newborns has previously produced a litter sexually—meaning scientists now believe that boa females possess the ability to actually alternate between both sexual and asexual reproduction.
Scientists say that if the boa’s new babies can reproduce sexually, all of those offspring will be female in gender—genetically incapable of producing males. Skipping a generation, only their female offspring can produce new male boas.