Neither vertebrate was peculiarly robust, but the information that they survived beyond hatching is simply a large deal. “I deliberation it's 1 of the astir important studies successful the tract of parthenogenesis and birds successful a agelong time,” says Warren Booth, an evolutionary biologist astatine the University of Tulsa who studies facultative parthenogenesis successful snakes and was not progressive successful this paper. He says that though sharks and rays produced done asexual reproduction person survived and adjacent thrived, the aforesaid hasn’t been seen successful birds. Parthenotes calved to domesticated turkeys, chickens, quails, zebra finches, and pigeons person astir each died earlier hatching.
Although these condors died young, Booth says, “This gives america immoderate accusation that possibly wrong raptors, we mightiness spot the quality to nutrient healthy—or astatine slightest surviving and somewhat viable—parthenogens that could past perchance reproduce wrong that population.”
Most vertebrates reproduce sexually, mixing familial accusation from antheral and pistillate partners to make offspring with a caller operation of genes. This statement has immoderate utility: If an embryo inherits a faulty transcript of a cistron from 1 parent, the transcript from the different genitor tin compensate.
But sometimes animals with peculiarly past genomes—including birds, lizards, sharks, and snakes—leave the antheral retired of the equation and reproduce asexually. Like mammals, females of these taxon nutrient eggs done meiosis, the process successful which chromosomes are pulled apart. The pieces are divvied up among 4 abstracted cells, lone 1 of which is an egg. During intersexual reproduction, an ovum merges its familial worldly with that of a sperm produced by a male. But during parthenogenesis, the ovum alternatively merges backmost unneurotic with 1 of the different cells, creating a self-fertilized egg.
Parthenotes tin lone beryllium 1 sex, though which enactment depends connected their species. For snakes similar boas and pythons, parthenotes are each female: Their chromosomes are XX.
Unlike humans, for birds it’s the egg, not the sperm, that dictates the enactment of the embryo. For that reason, scientists usage a antithetic naming strategy for their chromosomes. A pistillate has ZW chromosomes, portion a antheral has ZZ. If a pistillate reproduces asexually, that means she tin lone make a WW oregon ZZ embryo. But a WW successful birds wouldn’t make a viable embryo, truthful each avian parthenotes that past to the ovum signifier and beyond person to beryllium ZZ—male.
Usually, parthenogenesis happens among females erstwhile there’s nary antheral mate available. In theory, this mechanics allows the pistillate to support the cistron excavation going until a suitable antheral comes along. But it’s not an perfect solution, says Booth. Because the ovum is fusing with a compartment that contains a astir identical acceptable of chromosomes, there’s astir nary familial diverseness successful the resulting offspring. “Across astir of its genome, it lacks diversity, which is wherefore we spot successful astir cases of pathogenesis, the animals don't bash good agelong term,” helium says. “They're conscionable the astir inbred that you could be.”
But Demian Chapman, manager of the Sharks and Rays Conservation Program astatine Mote Marine Laboratory successful Florida who has identified respective antithetic parthenotes successful sharks and rays, points retired that portion they are much apt to person familial flaws, the ones that bash past whitethorn beryllium escaped of immoderate of the lethal cistron variants communal successful a species. “They can’t perchance beryllium carrying them, due to the fact that if they were carrying them they would dice due to the fact that they don’t person the different 1 to compensate,” helium says.
English (US)