While male bass undergo their own sex change, a new study has found that the Wolbachia genus of bacteria is able to change the sex of its hosts by silencing the immune system.

Scientists discovered male small and largemouth bass were changing their sex as early as 2003. This continues to affect the fish all across the United States.

But Wolbachia infect only arthropods (exoskeletal animals): insects, spiders, nematodes, crustaceans, et cetera. They are only able to spread the eggs of a species, not through the male’s sperm. Accordingly, when infecting a male, they will either kill the male or turn him into a female. A sort of compromise will allow the male to continue life as before, but can only impregnate females infected by the same species of Wolbachia. Infected females are capable of virgin birth.

This has made Wolbachia extremely common, found in about 70% of all species of arthropods. Within a species, Wolbachia typically infect more than 90% or less than 10%.

While the actual hormonal process is still being studied, researchers have learned that the Wolbachia implant parts of their own DNA into the host. Furthermore, it decreases production of the protein that detects invaders.

While Wolbachia can only last inside the human body for three days, the nematodes they infect can in turn infect us. The Wolbachia then lives off the nematode, and causes anything from blindness to elephantiasis (known more commonly as elephantitis).

Scientists now look to Wolbachia to help spread anti-malaria treatments, previously developed but with no way to spread effectively.

As for the bass, there is still no hypothesis about the cause of their transformation.

http://www.sciencedaily.com/releases/2010/01/100114143021.htm

http://news.nationalgeographic.com/news/2010/01/100126-sex-puppeteers-wasps-parasites-virgin-birth-sex-changes/

http://news.nationalgeographic.com/news/2007/07/070712-butterflies.html

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2327208/

http://www.washingtonpost.com/wp-dyn/content/article/2006/09/05/AR2006090501384.html

http://www.greenchange.org/article.php?id=4947

http://www.parade.com/news/intelligence-report/archive/100131-scientists-investigate-freaky-fish.html