Lighting the way: SU researchers study glow-in-the-dark sperm to learn more about fertilization
To determine which sperm fertilizes an egg after mating, scientists in Syracuse University’s biology department are using glow-in-the-dark sperm.
“I’m interested in sex,” said Scott Pitnick, a biology professor leading the research. “I’m an evolutionary biologist, and sex, obviously, is the powerful force for driving evolutionary change. Evolution is all about differential reproductive success, and sex is what’s driving things.”
Pitnick, who specializes in studying insects, and his team of researchers utilized genetically engineered green- and red-colored sperm to help understand and observe the changes at work within female fruit flies after insemination and during fertilization. The team hopes to eventually apply the research beyond fruit flies.
The work resulted in an article, “Resolving Mechanisms of Competitive Fertilization Success in Drosophila Melanogaster,” by research associate Mollie Manier, professor John Belote and Pitnick, published in the March 18 issue of Science Magazine.
While this research is not the first to use fluorescent sperm, it is the first study to employ two different colors of sperm, Manier said.
The study focused on how individual sperm compete to fertilize eggs. Illuminating the sperm’s head red or green allowed the researchers to see what sperm do within the female, providing the chance to decipher sperm competition, Manier said. The flies were used because of their simple genetics, reproductive physiology and developmental biology.
“It’s not just male-male competition with females being passive vessels,” Pitnick said. “Females play a very active role because they have a vested interest in their evolutionary fitness. Females have evolved ways of biasing fertilization in favor of one male’s sperm or another — we’re trying to understand how selection’s acting on females.”
Despite the commonplace belief that sperm are inactive, the study proved sperm are constantly moving and have the ability to swim backward and move their heads, Manier said.
The research has also shown that the female reproductive system in fruit flies has evolved into a large reproductive tract that can hold sperm for weeks, in order to better the chances of selecting the best sperm.
“Flies can keep sperm alive for many weeks, and because females mate many times during that period, different males’ ejaculates overlap within the female and are hence going to be competing,” Pitnick said.
Now, with the colored sperm, the researchers can look at winners and losers during competition, measuring male traits and figuring out what makes a male successful in sperm competition, Pitnick said.
This type of research cannot yet be applied to humans, Manier said, but the research will continue on fruit flies and may potentially relate to humans in the future.
Published on March 23, 2010 at 12:00 pm
