Today I found out that there is a protozoa that has seven sexes.

This organism is known as Tetrahymena thermophila.  They are species of ciliate protozoa, common in fresh-water. They are also known for being widely used in genetic and cytological research as model organisms.

The seven sexes of Tetrahymena thermophila are somewhat uninventively named I, II, III, IV, V, VI, VII and aren’t evenly distributed within a population thanks to the peculiar way each individual’s sex is determined. Unlike with say, humans, the genotypes of Tetrahymena thermophila don’t determine what sex they are, rather just provide probabilities of developing into a certain sex. These probabilities are influenced partly by genetics and partly by surrounding temperatures.

What scientists are still scratching their heads about is the reason why any species would develop to have seven sexes. The leading theory is that perhaps it gives somewhat of an advantage over a typical two sexed system of procreation in that any one sex can successfully mate with any other sex but its own.  Thus, having many sexes increases the odds significantly that one Tetrahymena thermophila will encounter another Tetrahymena thermophila that it can successfully mate with.

Bonus Facts:

• On the other end of the “number of sexes” spectrum is the whiptail lizard; all whiptail lizards are female. In order to create a new generation of whiptail lizards, these lizards use a system similar to cloning.  Interestingly though, in order for the females to reproduce, they do have to get it on with another female, even though the act itself is just simulated. One of the females will act out the role of a male mounting the other female.  After doing so, they will trade places.  This act doesn’t actually transfer any genetic code from one to the other or anything of the sort.  Rather, it simply stimulates egg production in both female lizards who then produce more or less copies of their own genetic code in their offspring.
• The black widow spider eats her mate during or after sex.  I have an ex who was kind of like that…
• There is an unusual tourist attraction in Manitoba, Canada – the annual mating of red-sided garter snakes. When a female garter snake, also known as “the town bike”, emerges from hibernation, she releases a pheromone that attracts hundreds of male snakes and they create a large ‘mating ball’.  Interestingly, the female can store the semen from the males for several years before ultimately incubating baby snakes in her lower abdomen.

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