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Lost a Few Genes There, Eh?

When the roundworm Caenorhabditis briggsae became capable of self-fertilization, that ability may have triggered the loss of thousands of genes, the New York Times reports.

"Many of these genes had been around, and were presumably needed, for tens of millions of years or longer," senior author Eric Haag from the University of Maryland tells the Times.

Haag and his colleagues noted that C. briggsae has far fewer protein-coding genes than its out-crossing sister worm C. nigoni. As they reported last week in Science, they aligned the C. briggsae and C. nigoni genomes to work out which genes were present in one, but not the other, worm. They found a difference of 6,854 genes between the two. They noted that ones missing in C. briggsae are typically expressed by male C. nigoni. These included members of the male secreted short (mss) gene family, which encodes glycoproteins presented on the surface of sperm.

When the researchers added mss genes to male C. briggsae — the Times notes that, though rare, there are some male C. briggsae — they were able to have more offspring, indicating that it improves male reproductive success.

"This bolsters the scientists' hypothesis that C. briggsae's dramatic reduction in DNA had to do with its change in sexual strategy," the Times adds.