California Condors Can Perform Asexual Reproduction

No single bird is more powerful, but the fact that they survive beyond hatching is a big deal. “I think this is one of the most important studies in the field of parthenogenesis and birds in a long time,” said Warren Booth, an evolutionary biologist at the University of Tulsa who studies the facultative parthenogenesis of snakes and no join this role. He says that although sharks and shark produced through asexual reproduction have survived and even evolved, the same has not been seen in birds. Parthenotes born to domesticated turkeys, chickens, vultures, zebra finch, and pigeons almost all die before hatching.

Although these condors died young, Booth said, “It gives us some information that maybe inside raptors, we can see the ability to produce healthy — or at least alive and relatively alive — animals. parthenogens that can reproduce within that population. “

Most vertebrates reproduce sexually, mixing genetic information from male and female partners to produce offspring with new combinations of genes. This arrangement has several uses: If an embryo inherits an incorrect copy of a gene from one parent, the copy from the other parent can be paid for.

But sometimes animals with much older genomes – including birds, lizards, sharks, and snakes – leave the male in the equation and multiply asexual. Like mammals, females of these species produce eggs through meiosis, the process by which chromosomes are pulled. The pieces are divided into four separate cells, only one of which is an egg. During sexual reproduction, an egg combines its genetic material with a sperm produced by a male. But during parthenogenesis, the egg in turn fuses with one of the other cells, forming a self-fertilized egg.

Parthenotes can only be of one sex, whichever sex depends on their species. For snakes like boas and python, the parthenote is female all: Their chromosomes are XX.

Unlike humans, for birds the egg, not the sperm, dictates the sex of the embryo. As a result, scientists use a different system to name their chromosomes. The female has a ZW chromosome, while the male has a ZZ. If a woman breeds asexual, that means she can only produce one WW or ZZ embryo. But a WW of birds cannot produce a living embryo, so all avian parthenotes that survive up to the egg stage and beyond must be ZZ-male.

Typically, parthenogenesis occurs in females when no male partner is available. In theory, this mechanism allows the female to continue the gene pool until a suitable male arrives. But this is not an ideal solution, according to Booth. Because the egg mixes with a cell with almost the same set of chromosomes, there is virtually no genetic diversity in the resulting offspring. “In most of its genome, it lacks diversity, so we see in most cases of pathogenesis, animals don’t do well over a long period of time,” he said. “They’re just the most inbred you can have.”

But Demian Chapman, director of the Sharks and Rays Conservation Program at Florida’s Mote Marine Laboratory who has identified several different parthenotes in sharks and rays, points out that while they are likely to have genetic defects, the survivors be free. of some of the lethal gene variants common to a species. “They can’t carry it, because if they carry it they will die because they don’t have one to pay for,” he said.

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