In The Field

Testes all over at SDB 2008

I once had an English teacher who gave copious quizzes. Once, when someone complained about the work, he replied, “If you think my quizzes are bad you should see my testes.” It was an all-boys Catholic school, which explains how he could get away wish such crude sentiments. Nevertheless, I saw a talk about an organism that would put him and his abundant quizzes to the shame he deserves. The planarian, a flat, freshwater dwelling worm with comical eyespots and a superlative reputation for regeneration has another surprise under its belt. In addition to two ovaries just south of its tiny brain, the sexual form of some planarians has dozens of testes spread throughout its body. These are hardly exempt from the famous regenerative qualities of the planaria which can regenerate from just a tiny portion, but they grow back in ways that were interesting to the attendees at this morning’s talk on stem cells and development. Philip Newmark of the University of Illinois at Urbana-Champaign showed how when you decapitate a planarian, the testes in the body disappear as the head regrows, only once the whole animal is intact does it resume it’s production of sperm. And when starved the animals resorb the plentiful sex organs until the food returns. When Newmark’s group fed the worms bacteria engineered to produce short interfering RNAs for a specific gene called nanos, they were able to block the testes regeneration even though the animal developed fine and had no obvious defects, looking somewhat like their asexual counterparts. They’re using this model to find other genes that might be important in testes regeneration and development.


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