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Parthenogenesis: Sexless Reproduction is a Useful Quality

Parthenogenesis is the asexual reproduction of a creature without the benefit of a male of the species. There are both benefits and problems with sexless reproduction.

Reproduction without Sexual Coitus: Is it Cloning?

Actually yes. Parthenogenesis, defined as a form of asexual reproduction in females of certain species that produces an exact replica of itself (basically, a 'clone') by the development of an unfertilized egg into an embryo. There are a number of invertebrate species which do this naturally such as aphids, nematodes, a few of the scorpion species, some crayfish species, water fleas and more.

A few of the vertebrate species that can undergo parthenogenesis naturally include notably the turkey, a few species of reptiles such as certain types of gecko, and some hammerhead sharks. This mode of reproduction can be induced in these and as well as other species, usually by the modality of an electric shock or some other instigating agent.

Parthenogenesis differs from hermaphroditic reproduction in that the latter is either a species or a particular specimen that possess the reproductive organs of both the male and female.

One such reptile noted for parthenogenesis is the New Mexico Whiptail Lizard whereby nearly the entire population is composed of females. Even some female snakes have been discovered to be parthenogenic that when raised in isolation produced clutches of self-fertilized eggs which subsequently hatched.

Only a few years ago it was documented that the Komodo Dragon species is capable of parthenogenesis. This is postulated to be a survival trait that has aided them in populating diverse islands separated by great expanses of water. The ability of the Komodo Dragon to reproduce asexually by parthenogenesis may also explain the unusual fact that nearly 75% of the population is male. This ratio would be unsustainable in a strictly sexual reproductive species.

In a recorded case of parthenogenesis, a female Komodo Dragon did switch back to normal sexual reproduction after an asexual occurrence. Having a male inseminate a female in sexual reproduction when the condition allows it would favor genetic diversity.

Is There any Good of Parthenogenesis?

There are both benefits and downsides to parthenogenesis. The 'exact copy of self' can lend itself to undesirable mutations which if they occur could affect an entire generation of individuals. There are benefits to parthenogenesis as well.

Not requiring the presence of the males which in most animal species tends to be aggressive to rival males and sometimes even against the female herself is one benefit. In the species common green iguana, if two males rival for one female a battle ensues until one male is either killed or withdraws. But if there are more than several males present when a female is in estrus and ready to mate, any male may kill the female instead of battling the challengers for the right to mate! The accepted notion is that this prevents rival males from procreating, from spreading their genes. Basically a 'if I can't have her, nobody will' condition.

In the case of poultry farming with domestic turkeys this could be devastating to the financial bottom line. Not only in loss of individuals but the stress that constant fighting makes the product less than desirable for market.

With turkeys at least, parthenogenesis is definitely a good thing. Domestic turkeys are bred to favor parthenogenesis so science and animal husbandry in particular are encouraging this trait in the domestic bird.

a turkey in a grassy yard

(image source)

One common fact is that parthenogenesis is good in the case of turkey farming (where by some estimates nearly 40% are the result of asexual parthenogenesis) is that prize specimens bred specifically for size, meat-to-fat ratio (leanness) and other body attributes (wide breasts, meaty legs, bone size & density, etc.) can be replicated almost endlessly. The acquired traits are exactly duplicated in the parthenogenic offspring, maximizing profits.

Get it right once and you've got potentially thousands more just like it; a virtual cash cow situation.

As I understand it, most marketed frozen turkeys are female for this reason, and that female turkeys being smaller than the male is of a more ideal size and weight. A 10-15 lbs. female turkey would be a better demographic fit for consumers than the 30-40lbs. male bird, assuming both were adults at the time of slaughter.

Also for the case of farm-raised turkeys that have any free-range privileges (if such a thing still exists these days, -I recall seeing many hundreds of flightless white domestic turkeys at an outdoor turkey ranch once) is that the males would tend to fight each other in 'harem building.' The males have large spurs on their ankles and could do a lot of damage to an opponent.

This fighting and subsequent rounding-up of females into collective breeding harems is greatly reduced if fewer males are required for maintaining genetic diversity. The females regulate their own reproductive cycles and the males are just around to ensure that mutations due to parthenogenic cloning are keep in check.

-There are just too many female turkeys for any male to fight over.

Parthenogenesis would be tremendously profitable if it could be recreated with larger stock animals such as sheep, horses and especially cattle. The beef cattle industry would love that; a prize specimen bred for size, weight, disease-resistance and physical features etc. could be reproduced nearly endlessly in exact duplication. Unfortunately, this is something that science says is decades away from the possible, if ever. The genome of higher animals (that includes humans) is just too complex for parthenogenesis to occur naturally or artificially at this time.

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Comments (7)

Another fabulous and so well researched article. I learned something new from you, thanks :)

Really interesting read. I can see why farmers would profit from Parthenogenesis and I can understand why some creatures have adapted to reproduce this way. I watched a program about jumping gender frogs that changed their sex to mate, so if a male was available it would turn into a female etc. It is a scary thought as in Nottingham where I live there are loads more females than males!! glad I have had all my babies.

Brilliant discussion of an original topic

A weird fact: With the Percula clownfish "(the "Finding Nemo") in a mated pair if the females dies, the male switches gender to female and another 'attendant' Percula will take the place of the male, -even if that attendant was formerly female (which changes gender to male..) Mated pairs of Percula in the wild are often surround by a quarter-dozen 'attendant' Perculas of non-gender. They do not care for the young or cause any threat. Having no gender yet, they are not in competition to breed but they may be waiting for opportunity to 'take over' the anemone in the method described.

I think the world would be a happier place if we were all like the Percula!

Very interesting article dealing with a different and unique subject matter! Excellent work stickman, very educational.

The early Greeks were passionately devoted to parthenogenesis. Reading The Cult of Divine Birth by Marguerite Rigoglioso is a must for anyone sincerely interested in this ancient/modern subject. For starters though, one should read the following blog/article: www.thestoryoflaurie.blogspot.com I've been researching and contemplating parthenogenesis since 1969. Critical thinkers are welcome. Don't worry, this article transcends orthodox religion and is steeped in enough science to really make one wonder if it's real, or not. Good luck!

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