(Host) Sex is of course central to evolution. Some organisms have discovered that there’s no need to depend on original Nature. Commentator Ruth Page reports that they just alter others’ sex to suit themselves.
(Page) When Noah gathered creatures on the Ark, he had to have two of each, male and female. Yet we know now that some creatures don’t need to mate to produce young. And that sex isn’t pre-determined. Among alligators and turtles, eggs can produce males or females depending on the local temperature.
Out there in the vast, non-human world, sex life can be a game of roulette. Infectious organisms play sex games with many invertebrates, leaving genes gasping on the mat. A recent Natural History magazine showed how insidiously parasites cause sex-changes in invertebrates. One protozoan infects an animal’s eggs, then makes its home in the cells of little shrimp in European tidal pools. The protozoan can only develop in female shrimp eggs. No problem. If it lands in a male, it turns him into a female. The shrimp only survive because four-fifths of them don’t get infected.
Other parasites simply kill the sons of their host creature and infect the females, who of course pass on the infection to their daughters. Another one-celled critter is transmitted through the eggs of infected female mosquitoes, where it kills the male larvae eggs. Any that happen to infect males develop into specialized spores that can no longer infect mosquitoes; now they can infect copepods.
Any female copepod that eats a dead male mosquito ingests the spores that turn her ovaries into a spore-producing machine to churn out spores that CAN infect mosquito larvae.
Various bacteria simply kill the males of fruit flies, wasps, butterflies and beetles, because only infected females can carry on their species. There’s an African butterfly species in which so many males die, the females have to gather in large assemblages in order to attract the few males. The butterfly males have a great but exhausting time, and many females remain wall-flowers.
Bacteria of the genus Wolbachia can infect a wide variety of invertebrates, in some cases changing males to females, in some cases killing males, and in some cases making their female hosts parthenogenetic (able to produce young with no male help). Sometimes killing the infectious bacteria makes the insect revert to sexual reproduction; but in other cases it’s too late: the insect can no longer reproduce sexually. Such insects can only reproduce with the help of parasites.
There are also Wolbachia that make eggs from uninfected females incompatible with sperm from infected males. They can only reproduce when both sexes are infected, thus helping Wolbachia. Another Wolbachia strain enters a special bean borer moth and turns the male host into a female. Put it into a common flour moth and it kills the males. Whatever works.
This is Ruth Page suggesting that sex education looks more complicated than we thought.