Featured Research

from universities, journals, and other organizations

Slower, longer sperm outcompete faster rivals, surprising finding shows

Date:
August 1, 2012
Source:
Syracuse University
Summary:
When it comes to sperm meeting eggs in sexual reproduction, conventional wisdom holds that the fastest swimming sperm are most likely to succeed in their quest to fertilize eggs. That wisdom was turned upside down in a new study of sperm competition in fruit flies (Drosophila melanogaster), which found that slower and/or longer sperm outcompete their faster rivals.

For sperm, faster isn’t always better.
Credit: Image courtesy of Syracuse University

When it comes to sperm meeting eggs in sexual reproduction, conventional wisdom holds that the fastest swimming sperm are most likely to succeed in their quest to fertilize eggs. That wisdom was turned upside down in a new study of sperm competition in fruit flies (Drosophila melanogaster), which found that slower and/or longer sperm outcompete their faster rivals.

The study, recently published online in Current Biology and forthcoming in print on Sept. 25, was done by a team of scientists led by corresponding author Stefan Lüpold, a post-doctoral researcher in the Department of Biology in the College of Arts and Sciences. The team made the discovery using fruit flies that were genetically altered so that the heads of their sperm glow fluorescent green or red under the microscope. The fruit flies, developed by biology Professor John Belote, enable researchers to observe sperm in real time inside the female reproductive tract.

"Sperm competition is a fundamental biological process throughout the animal kingdom, yet we know very little about how ejaculate traits determine which males win contests," says Lüpold, a Swiss National Science Foundation Fellow working in the laboratory of biology Professor Scott Pitnick. "This is the first study that actually measures sperm quality under competitive conditions inside the female, allowing us to distinguish the traits that are important in each of the reproductive phases."

The research is also significant because the scientists studied naturally occurring variations in sperm traits, rather than manipulating the test populations for specific traits. After identifying and isolating groups of males with similar ejaculate traits that remained constant across multiple generations, the scientists mated single females with pairs of males from the different groups. "This approach allowed us to simultaneously investigate multiple ejaculate traits and also observe how sperm from one male change behavior depending upon that of rival sperm," Lüpold says.

Female fruit flies mate about every three days. Sperm from each mating swim through the female bursa into a storage area until eggs are released. Eggs travel from the ovaries into the bursa to await the sperm. However, sperm battles actually take place within the storage area. After each mating, new sperm try to toss sperm from previous matings out of storage. The female then ejects the displaced sperm from the reproductive system, eliminating the ejected sperm from the mating game. The researchers observed that longer and slower-moving sperm were better at displacing their rivals and were also less likely to be ejected from storage than their more agile counterparts.

"The finding that longer sperm were more successful is consistent with earlier studies," Lüpold says. "However, the finding that slower sperm also have an advantage is counterintuitive."

Why slower sperm have an advantage is still open to speculation. "It could be that, when swimming back and forth in storage, slower sperm hit the exit less frequently and are therefore less likely to be pushed out," Lüpold says. "Or, because sperm velocity is dependent on the density of sperm within the narrow storage area, it could be that velocity isn't really the target of sexual selection in fruit flies, but is rather a consequence of the amount of sperm packed into the storage organ."

The U.S. National Science Foundation (NSF) and the Swiss National Science Foundation funded the study.


Story Source:

The above story is based on materials provided by Syracuse University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Stefan Lüpold, Mollie K. Manier, Kirstin S. Berben, Kyle J. Smith, Bryan D. Daley, Shannon H. Buckley, John M. Belote, Scott Pitnick. How Multivariate Ejaculate Traits Determine Competitive Fertilization Success in Drosophila melanogaster. Current Biology, 2012; DOI: 10.1016/j.cub.2012.06.059

Cite This Page:

Syracuse University. "Slower, longer sperm outcompete faster rivals, surprising finding shows." ScienceDaily. ScienceDaily, 1 August 2012. <www.sciencedaily.com/releases/2012/08/120801143728.htm>.
Syracuse University. (2012, August 1). Slower, longer sperm outcompete faster rivals, surprising finding shows. ScienceDaily. Retrieved October 23, 2014 from www.sciencedaily.com/releases/2012/08/120801143728.htm
Syracuse University. "Slower, longer sperm outcompete faster rivals, surprising finding shows." ScienceDaily. www.sciencedaily.com/releases/2012/08/120801143728.htm (accessed October 23, 2014).

Share This



More Health & Medicine News

Thursday, October 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Ebola Fears Keep Guinea Hospitals Empty

Ebola Fears Keep Guinea Hospitals Empty

AP (Oct. 23, 2014) — Fears of Ebola are keeping doctors and patients alike away from hospitals in the West African nation of Guinea. (Oct. 23) Video provided by AP
Powered by NewsLook.com
Orthodontist Mom Jennifer Salzer on the Best Time for Braces

Orthodontist Mom Jennifer Salzer on the Best Time for Braces

Working Mother (Oct. 22, 2014) — Is your child ready? Video provided by Working Mother
Powered by NewsLook.com
U.S. Issues Ebola Travel Restrictions, Are Visa Bans Next?

U.S. Issues Ebola Travel Restrictions, Are Visa Bans Next?

Newsy (Oct. 22, 2014) — Now that the U.S. is restricting travel from West Africa, some are dropping questions about a travel ban and instead asking about visa bans. Video provided by Newsy
Powered by NewsLook.com
More People Diagnosed With TB In 2013, But There's Good News

More People Diagnosed With TB In 2013, But There's Good News

Newsy (Oct. 22, 2014) — The World Health Organizations says TB numbers rose in 2013, but it's partly due to better detection and more survivors. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins