Like a Virgin, Prasad, Aarathi [free children's ebooks pdf .TXT] 📗

been revealed that things are not so simple (or so very human). The male little fire ants appear to be clones, without any of their mother’s DNA, but this trait appears to be controlled by the females – or more specifically, by the queen ant. Only males mated to the queen can become clones of their fathers, which is to say that, if a son ditches its maternal DNA, it is because the mother has dictated it to do so.

For the little fire ant, it seems there would be no male clones if the females themselves were not able to have virgin births. When the cells in a queen divide to produce parthenogenetic eggs, there is not an equal division. One of the two ‘daughter’ cells takes the DNA-containing nucleus in its entirety, while the other takes just the cell’s cytoplasm. So a queen lays some eggs that have a complete set of DNA and require no fertilization (and which become sterile daughters) and lays eggs that are ‘empty’, with no nucleus or DNA. Should these empty eggs be fertilized by sperm, the only DNA to be donated to the embryo comes solely from the male – there simply is no genetic information from the mother ant in the egg.

In other species, parthenogenesis is triggered by the sort of hazard that some scientists believe gave rise to sex in the first place: a contagious infection. Believe it or not, this means that you might be able to ‘cure’ some animals from the plague of virgin births – animals like stingless wasps (Trichogramma). These tiny parasites make their living with some rather cunning tricks. The females attack the eggs of moths and other species, injecting their own eggs into those of their unsuspecting victims. In some cases, they find newly hatched eggs via some quite sophisticated chemical espionage. The wasps can sense anti-aphrodisiacs – the pheromones that many male insects pass to females to signal that mating has taken place, and which makes these females less attractive to other males, in an attempt to keep other males’ DNA from competing in a race to fertilize the egg. This may be a useful tactic to employ when there is competition for females, but it’s also a communication system prone to sabotage by the stingless wasp. By following the scent of these pheromones, the wasps can locate a female butterfly, moth, or other insect that has just mated and is poised to lay a clutch of eggs. The female wasp then hitches a ride on her hostess insect, until the host lands on a plant to lay its eggs. The parasitic passenger hops off and quickly injects its own eggs inside the fresh host eggs, so that when the wasp’s larvae develop, they are perfectly placed to eat the contents of the victim eggs. And these host insects are not the only victims. For the female wasps themselves play host to another parasite, one yet more brilliant. When this parasite infects its target, the males of its host species become infertile, or are killed while they are still developing as embryos. And as the males are eradicated, their females begin having virgin births. This is probably how stingless wasps began to reproduce in this way – and why they may yet be kept from transforming into an all-female species.

The parasite responsible for infecting the stingless wasp is the Wolbachia bacterium. Wolbachia live in the eggs of the host wasp, through them passing from mother to young. But these tiny wasps are not their only targets: Wolbachia are among the most abundant and remarkably widespread of all parasitic bacteria, and the number of species known to be infected by the bacteria is increasing rapidly. Just how far afield Wolbachia are distributed is uncertain, but so far, they have been found in over seventy-five percent of arthropods, which include eighty insect species, seventeen isopods (a category of crustaceans that includes the woodlouse), many spiders, and one type of mite. It is also likely that there is probably an equivalent proportion of infections among nematode worms. And there is a good chance that it will spread.

If this doesn’t seem like much to be concerned about, bear in mind that between them, arthropods and nematode worms comprise something in the order of 99.99 percent of animal species in the world. From cockroaches to termites, dragonflies to ladybirds, woodlice to worms, Wolbachia wreaks havoc with ovaries, testes, eggs, and sperm in many ways – not all of which are entirely clear. What is clear is that Wolbachia need eggs; they live in them. This means that the bacteria must be assured of a good supply of eggs – and in this respect, males are dispensable. So Wolbachia has found a way to make the eggs of stingless wasps develop without any sperm involved.

When the wasps reproduce through parthenogenesis, they produce only daughters, of course. But in 1990, scientists found that they could make females and males start having sex again, and that they could induce mothers once again to have sons. All it took was a dose of antibiotics.

Wolbachia may be the most prevalent bête noire of male insects, but it is by no means the only parasite to play this game. There is a parasitic fungus, Ichthyophonus hoferi, that causes parthenogenesis epidemics in fish worldwide. Among its targets is the green swordtail (Xiphophorus helleri), a species in which the female fish is able to turn into a sperm-producing, fully functional male, indistinguishable from a true male. In the fish, the fungus causes haemorrhages, destroys muscle, and rots fins and skin – so there is reason to worry about its effects. One of the toxins it produces also seems to make eggs develop without sperm. In addition, there is a large and diverse array of micro-organisms that alter the ratio of