A new study by UW-Madison and University of Alberta scientists published Friday in the highly respected journal \Science"" proves male worms thrive in harsher conditions in comparison to worms of the other gender, hermaphroditic worms.
Caenorhabditis elegans, the millimeter-long worms used in these experiments, are either male or hermaphrodite-a chromosomal female with a small amount of sperm for self-reproduction.
Researchers found that under harsh environmental conditions, an offspring of a male and hermaphroditic worm may be able to change its genetic makeup and gender after birth.
Researchers looked to answer why male worms exist when a hermaphrodite can reproduce itself.
""If you try to mate young hermaphrodites with males, they are not eager to mate [because they have their own sperm],"" said Veena Prahlad, UW-Madison research associate in genetics. ""But when [hermaphrodites] are older, and don't have as much sperm or are under harsher environmental conditions, there are more advantages to mating with a male.""
Researches speculate there are advantages for hermaphrodites to mate with males. In self-fertilization, a hermaphrodite produces an exact clone of itself. This may create a problem if there is a genetic mutation in a worm's chromosome because the mutation would continue down the line of offspring. If there is a mutation, this may inhibit the worm's ability to adapt to the environment.
Therefore, if a hermaphrodite mates with a male worm, there may be a better chance for an offspring to rid itself of genetic mutations, making it easier to adapt to surroundings. Researchers also found a hermaphroditic offspring produced by a male and hermaphrodite may be able to change their gender to male. Hence, an offspring is more likely to change gender to a male if the surroundings are stressful, experts said.
""In order to respond to their [harsh] environment, they lose a chromosome, becoming male,"" said Liana Lamont, a UW-Madison graduate student. ""In this study, the harsh environment was produced by starving conditions where the worms were deprived of food, or exposed to certain chemicals produced by a bacteria called metabolite.""
The worms regularly consume the bacteria strain Escherichia coli as a food source and were then exposed to one of the byproducts, metabolite.
Elizabeth B. Goodwin, associate professor of genetics at UW-Madison and principle investigator explained the phenomena from the beginning of fertilization.
""Both offspring [one made solely by self-fertilization, and one by cross-fertilization] start out with two X chromosomes, one from a dad and one from a mom,"" Goodwin said. ""The paternal or dad's chromosome is somehow marked, such that it would behave differently when encountering the bacteria.""
Although researchers are unsure what conclusions to draw from the study, Goodwin predicted ""males could be more active, or better at something, better at adapting. There are a variety of possibilities.\
