No matter how it's done, reproduction is weird, often wonderful and sometimes scary. Back in 2000, Bill Joy, chief scientist at Sun Microsystems, wrote an article in Wired magazine titled "Why the Future Doesn't Need Us." In it, he predicted that a catastrophic development was just around the corner: self-replicating robots. Once that eventuality had been reached, he feared, human life as we know it would shortly become irrelevant.
But you don't have to look to the future for examples of strange reproductive possibilities. In ancient Greece, Zeus, god of thunder and head honcho on Olympus, had a memorable encounter with childbirth. One day Zeus had a liaison with one Metis, goddess of craftiness. Too late, he remembered a prophecy that predicted Metis's children would be more powerful than their father. Worried about the consequences, he quickly swallowed his lover whole. Of course, it was too late — she was already pregnant. Sometime later, having developed a phenomenal headache, he got one of his fellow gods to chop his skull open with an axe. Out jumped his new daughter, Athena, goddess of wisdom, in full battle gear.
All this might sound improbable, but it's no stranger than some of the bizarre ways organisms are self-replicating in real life, right now.
Maybe it's because the reproductive process is so strange that humans have been telling stories about virgin births since storytelling began. The most famous of these tales is, of course, the one about the birth of Jesus Christ whose mother, Mary, is said to have conceived while still a virgin.
While it's technically possible for a woman to produce a virgin birth, it's incredibly unlikely. On the other hand, parthenogenesis (the scientific term for virgin birth) is common among other creatures in nature. Hammerhead sharks, komodo dragons, mole salamanders, and an assortment of other reptiles, fish and insects can all produce offspring without mating.
It all starts with something called a "germ cell." This germ cell splits in two, and then each of those halves splits again. Now you've got four reproductive cells, called gametes. Three gametes are discarded. The remaining gamete contains half the chromosomes necessary to create a new individual. In sexual reproduction, a female gamete and a male gamete fuse, creating a complete set of chromosomes.
But in parthenogenesis, the female gamete, or egg, contains a complete set of chromosomes and is able to stimulate itself to grow.
Incredibly, there are species of insects that go back and forth between parthenogenesis and sexual reproduction, depending on which method works best for the environment they're in at the time (e.g., is there a mate available?). Then there's something called cyclic parthenogenesis in which organisms such as water fleas alternate back and forth between mating and non-mating reproduction.
As yet, nobody's found any examples of parthenogenesis in mammals, but it's been artificially induced in rabbits, among other critters, with the help of temperature control and chemicals [source: ANSCI]. No luck with humans so far...
Let's not confuse parthenogenesis with hermaphroditic reproduction! They're not the same at all. In parthenogenesis, the female gamete does all the work single-handedly. Hermaphrodites, however, are remarkable for being able to produce both male and female gametes. That's because they have both male and female reproductive organs.
In some species, like certain flowers, snails and fish, hermaphroditism is common. Sometimes an organism might start off male and turn female; sometimes they might start off female and turn male; and sometimes they remain both sexes throughout their lifespan.
Remember Nemo and his dad in "Finding Nemo"? It turns out a sequel is warranted because there's a lot of drama in the reproductive lives of clownfish. Socially, clownfish like to hang out in sea anemones where two large breeders, a male and a female, are in charge of a group of smaller male clownfish who don't reproduce.
But say, for instance, the female breeder dies. In that case, the large male switches its sex to become the dominant female while the biggest of the small males quickly bulks up to take on the role of sexually mature male breeder [source: UCB]. Come on Pixar — "Becoming Nema" is a hit waiting to happen.
Clutch piracy is a breeding strategy that involves frogs sporting eye patches and wielding cutlasses while swigging rum.
Actually, no it's not. It does involve frogs, but they're naked and they live in the Pyrenees, not Barbados. Their lack of clothes is important — high in the Pyrenees, the nights are so chilly that frogs, who typically like to mate under the cover of darkness, are forced to get busy on sunny afternoons instead.
Thanks to this local peculiarity, researchers were able to keep a close eye on the process and observed a weird deviation from the usual ho-hum external fertilization they expected to see.
External fertilization is the preferred reproductive strategy of many fish and amphibians. The female lays a "clutch" of eggs in the water and then a male deposits some sperm on them. Frogs like to make sure this process is accomplished without delay. Typically when a female frog is ready to lay her eggs, she lets a male climb on her back and give her a big bear hug. She releases her egg clutch, and the male immediately fertilizes it. However, his sperm might fertilize only a percentage of the eggs in the clutch.
High in the ponds of the Pyrenees, frog romance works a little differently. Male frogs vastly outnumber the females. Because they often can't find a female to mate with, gangs of piratical males have taken to hunting for freshly laid egg clutches. As soon as they find them, they do their best to fertilize any of the unfertilized eggs that are left. Researchers have found clutches with as many as four different fathers! [source: Sanders]
Most flowers have an I-pat-your-back-you-pat-mine relationship with the pollinators that help them reproduce. Bees, butterflies and hummingbirds, for instance, get a delicious sip of nectar in return for carrying some grains of pollen from one flower to the next. Once this happens, the receiving flower can start the process of making the seeds that will grow into new flowers.
But certain species of orchids find this strategy old hat, not to say downright boring. With pollinators hopping from one flower to its neighbor, orchids worry about inbreeding. Well, as far as we know, they don't actually worry, but evolution has resulted in a far more novel — in fact truly bizarre — method of self-replicating for these organisms.
In mountainous regions of the Mediterranean, there's a species called Ophrys apifera, better known as the bee orchid. In an incredible trompe l'oeil effect, the flower looks precisely like the rear of a female bee with its head buried in a blue-petalled flower. Not only that, Ophrys mimics the scent of said female bee, and it's even a little furry to add to the sensory illusion. This deception is so perfect that even its seeming imperfections turn out to be advantageous.
Male bees, seduced by the floral wizardry, fall to mating so vigorously with the flowers that they dislodge pollen packs pre-loaded with a special adhesive that sticks to their backs. But according to plan, the deception only lasts so long. After some frantic efforts at achieving erotic bliss, the bee wises up to the fact that he's been had and staggers away in a fit of frustration. He'll wander a fair distance collecting his wits before he falls for the trick again and, if all goes well for perfidious Ophrys, unwittingly deposits his pollen payload in another bee orchid flower.
The bee's frustration plays into the orchid's reproductive strategy, as the distance traveled while the bee was cooling his temper prevents inbreeding [source: Pollan]. Of course, bees aren't the only ones seduced by orchid magic — think of all the orchid plants flowering on windowsills the world over.
Next time you cool off in a lake, try not to think about the fact that you might be surrounded by furry single-celled microbes engaging in some truly peculiar reproductive behavior. Actually, for the most part, Tetrahymena is quite a chaste creature that uses the virginal method of parthenogenesis to populate its fresh-water environs.
But parthenogenesis doesn't create the kind of genetic variation that can help organisms adapt to changing surroundings. So when times are tough, Tetrahymena can actually switch on a dormant sex drive to help it survive. That's when things get very interesting.
If you think keeping track of gender politics is complicated, consider the fact that this little creature has no fewer than seven genders! Scientists have imaginatively termed these genders Types I through VII. A Type I can't mate with another Type I, but not to worry — it can choose from among any one of the remaining six genders.
The new baby Tetrahymena get all the genetic info necessary to become any one of the seven possible types. Then, through a random process, their DNA gets pruned down to a single gender. Pretty complicated stuff for a microscopic microbe!
Most of us have mercifully forgotten the plot to the 1994 Schwarzenegger/DeVito vehicle "Junior." For the purposes of scientific edification, this article will do you the disservice of reminding you that it involves the future governor of California becoming pregnant. Hilarity ensues.
Absurd concept, of course, but show this comedic gem to a seahorse, and it would shrug its shoulders (if it had them). And that's not because the film received a 32 percent rating on the Rotten Tomatoes review site, but rather because there's nothing surprising about pregnant males in the seahorse world.
When seahorses get around to reproducing, the males and females engage in an elaborate, lengthy and apparently beautiful courtship dance in which they entwine their tails and swim in tandem. Eventually, with their movements fully synchronized, the female slips a couple thousand eggs into a little pouch the male has just for that purpose.
The male fertilizes the eggs and carries them around in his pouch where they hatch. He carefully tends to their needs as they grow, and when they're ready to head off into the world he actually has muscular contractions to push them out.
And now for some creepy parasitic procreation! When it comes to parasites, it's hard to choose from the array of weird, brilliant and often really troubling modes of self-replication. However, a lowly barnacle called rhizocephalans has a strategy so Machiavellian it deserves some attention here.
Rhizocephalans — we'll call it rhizo for short — doesn't look like your ordinary barnacle. As a young larva, rhizo floats around in hopes of encountering a passing crab. Given the size of the ocean, the chances are slim, but rhizos are produced in vast quantities, so a few are bound to find their targets.
Once a rhizo makes crab-fall, it latches on, develops a little syringelike appendage and injects its cells into the crab's system. The rhizo cells find their way to their host's sinus and there begin to grow a root system that spreads everywhere, eventually poking out in exactly the spot where a female crab would carry its eggs. The parasite then lays its own eggs there in a little sac.
For reasons not yet fully understood, if the crab happens to be a male it will actually change shape, widening its abdomen to more closely resemble a female. Also unknown is how exactly the rhizo convinces its host that the parasitic eggs it's carrying around are actually crab eggs. Then, as though in a scene from "Being John Malkovich," the parasite directs its host out to deeper waters where it can avoid predators and competition for food.
It's all a bit unsettling. But is it as disturbing as Hymenoepimecis argyraphaga? Read on to compare.
Hymenoepimecis argyraphaga is a parasitic wasp that makes its home in lovely Costa Rica. When in the mood to reproduce, a female wasp hunts down a hapless spider by the euphonious name of Plesiometa argyra and paralyzes it for 10 or 15 minutes with a sting. In that quiet quarter of an hour the wasp lays an egg, gently attaches it to the spider's belly and departs.
When the spider recovers it goes about its business as though nothing has happened. Perhaps it doesn't remember; perhaps it doesn't want to remember. All the while that wasp egg is incubating. A week or two later, the intermission is over, and things go rapidly downhill for Plesiometa. The wasp larva hatches, stabs a hole in the spider's stomach and begins feeding off it.
In a particularly diabolical move, the larva extracts one last resource from the spider before murdering it. The infant wasp injects some kind of psychoactive substance that convinces the poor thing to spin a very un-Plesiometa-like web. When it's done, the wasp kills the drug-addled arachnid, eats it and then uses the freshly spun web to wind itself into a cocoon.
Less than two weeks later a fully grown Hymenoepimecis argyraphaga emerges, prepared to propagate in the same horrific way [source: Gambino]. Isn't nature wonderful?
If, like seahorses, starfish look like creatures from a fairytale, the venomous invertebrate known as the crown-of-thorns belongs in one of those old, sinister Brothers Grimm versions.
Crown-of-thorns starfish (or more properly, "sea stars") eat coral reefs. Because of human activities such as overfishing of their natural predators, they can sometimes undergo a population explosion. This, in turn, can result in the complete destruction of a reef. Not only will this mean the loss of habitat for the many creatures that make their home in reefs, but the local tourist industry can be hit too.
To combat the problem, there have been various efforts the kill off the excess crown-of-thorns. On the Great Barrier Reef, for instance, divers started off by chopping the invertebrates into little pieces. The plan backfired because of the sea stars' remarkable ability to regenerate [source: Davis].
Not only can they regrow lost limbs, but under the right circumstances, they can grow a whole new body from a severed limb. That's because their cells are "indeterminate," which means they retain the ability to form new body parts, just as our embryonic cells did when we were first developing [source: Scienceline].
Now, if only we could master this regeneration thing — not only could we regrow lost limbs, we could generate whole new ones. Who couldn't use an extra pair of arms? Things would be a little weirder, though, if those disembodied arms grew a new you.
Teenagers can procreate. Terrified by this prospect, their parents often seek to exert whatever control they can over their children's sex lives. From a teenager's perspective it's all rather annoying having old farts incessantly minding your business. But before sighing heavily and rolling your eyes at mom's intrusions, spare a thought for the Japanese climbing fern. Compared to them you've got it easy.
Fully grown ferns are called gametophytes, and they can be males, females or hermaphrodites if there are no other breeders around to help out. But, of course, self-fertilization is the very incarnation of inbreeding, a situation to be avoided whenever possible.
So, when little fernlings are growing, older females in the neighborhood can secrete a chemical called gibberellin, which causes the surrounding youth to turn into males. Thus the grown-ups control the gender balance to maintain a healthy genetic diversity [source: Zastrow].
Of late, the word "community" has become a buzzword for all that is positive and necessary in 21st century life — perhaps the sex life of climbing ferns demonstrates that community involvement might have its limits!
Rabbits can be fluffy bundles of laziness or superbly rambunctious. Learn if rabbits really go crazy in March at HowStuffWorks.
Author's Note: 10 Weird Ways Organisms Reproduce
Parasitologists like to argue that the subjects of their research are to be respected for the ingenuity of their survival strategies. After researching and writing about a few of them, I have to agree that there's a kind of psychopathic brilliance on display, but it actually turned my stomach a bit. That Costa Rican wasp, for instance, is so thorough in its exploitation of the poor spider that it's hard not to feel there's something malicious about the whole process. But as cruel as evolution can be, there's also the naughty elegance of the bee orchid to admire.
- Danielson, Stentor. "Seahorse Fathers Take Reins in Childbirth." National Geographic. June 14, 2002. (Sept. 9, 2015) http://news.nationalgeographic.com/news/2002/06/0614_seahorse_recov.html
- Davis, Haley. "Crown of Thorn Sea Stars." University of North Carolina at Chapel Hill. 2007. (Sept. 11, 2015) http://www.unc.edu/courses/2007fall/masc/490/001/Coral Reef Decline/Crown of Thorns.html
- Encyclopedia Britannica. "Gamete" May 5, 2015. (Sept. 7, 2015) http://www.britannica.com/science/gamete
- Gambino, Megan. "Top 10 Real-Life Body-Snatchers." Smithsonian. Oct. 23, 2011. (Sept. 11, 2015) http://www.smithsonianmag.com/science-nature/top-10-real-life-body-snatchers-116692496/?no-ist
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- Pollan, Michael. "The Weird Sex Life of Orchids." The Guardian. Oct. 8, 2011. (Sept. 9, 2015) http://www.theguardian.com/science/2011/oct/09/orchid-sex-botany-ziegler-pollan
- Quirk, Trevor. "How a Microbe Chooses Among Seven Sexes." Nature. March 27, 2013. (Sept. 8, 2015) http://www.nature.com/news/how-a-microbe-chooses-among-seven-sexes-1.12684
- Sanders, Robert. "Clutch Piracy Revealed as Novel Mating Strategy in European Common Frog." UC Berkeley News. Sept. 15, 2004. (Sept. 8, 2015) http://www.berkeley.edu/news/media/releases/2004/09/15_piracy.shtml
- Simon, Matt. "Absurd Creature of the Week: The Barnacle That Invades Crabs in a Not OK Way." Wired. July 24, 2015. (Sept. 9, 2015) http://www.wired.com/2015/07/absurd-creature-of-the-week-rhizocephalan/
- UCB. "Gender-bending Fish." Understanding Evolution. (Sept. 8, 2015) http://evolution.berkeley.edu/evolibrary/article/fishtree_07
- University of California Museum of Paleontology. "The Haploid Life Cycle." (Sept. 8, 2015) http://www.ucmp.berkeley.edu/glossary/gloss6/haploid.html
- University of California Santa Barbara ScienceLine. "How Do Snails Reproduce?" 2015. (Sept. 8, 2015) http://scienceline.ucsb.edu/getkey.php?key=2578
- University of California Santa Barbara ScienceLine. "How do Starfish Create New Limbs?" 2015. (Sept. 11, 2015) http://scienceline.ucsb.edu/getkey.php?key=681
- University of California Santa Barbara ScienceLine. "How Is Pollination Different From Fertilization?" 2015. (Sept. 8, 2015) http://scienceline.ucsb.edu/getkey.php?key=185
- University of Wisconsin-Madison Department of Animal Sciences (ANSCI). "What is parthenogenesis?" (Sept. 7, 2015) http://www.ansci.wisc.edu/jjp1/ansci_repro/misc/project_websites_08/tues/Komodo Dragons/what.htm
- Zastrow, Mark. "Ferns Communicate to Decide Their Sexes." Nature. Oct. 23, 2014. (Sept. 11, 2015) http://www.nature.com/news/ferns-communicate-to-decide-their-sexes-1.16214