Featured Research

from universities, journals, and other organizations

Older Female Fish Prefer Imperfect Male Mates, Study Finds

Date:
November 15, 2005
Source:
Ohio University
Summary:
There’s hope for the less-than-perfect male – if you’re a swordtail fish, that is. As the size and age of female swordtail fish increase, so does the preference for males with asymmetrical markings, according to a new Ohio University study.

Biologist Molly Morris studies the mating preferences of swordtail fish.
Credit: Photo by Rich Fatica, Ohio University

There’s hope for the less-than-perfect male – if you’re a swordtail fish, that is. As the size and age of female swordtail fish increase, so does the preference for males with asymmetrical markings, according to a new Ohio University study.

Molly Morris, associate professor of biological sciences, and colleagues found that older female swordtails spent more time with asymmetrically striped males than symmetrical males when offered a choice. These findings are the first to contradict previous studies showing that females tend to prefer males with symmetrical markings, which in this case are black bars on each side of the body. Scientists have suggested that symmetrical markings are a sign of genetic fitness.

The new study provides evidence that visual cues are not the only thing driving mate selection, however. The findings also suggest that “females may not have the same mating preferences throughout their lives,” Morris said. Funded by the National Science Foundation and the Research Challenge Program at Ohio University, the paper has been published online in Biology Letters and will appear in next month’s print edition.

Morris’ findings raise the question of whether there may be a change in mating preference over time in other species as well. In a current study on human attraction, for example, the average age of the females and males tested for preference for symmetrical faces was only 20.3 years and 19.5 years, she said.

The swordtail fish used in the latest research are two species of Mexican fish, Xiphophorus cortezi and Xiphophorus malinche. Because the genetic makeup of these fish is well known, researchers often use them to examine genetic causes of behavior.

To conduct the study, Morris and colleagues exposed females of both species to video animations of male fish, one with an equal number of bar markings on each side of the body, and one with an unequal number of bars on each side. The animations simultaneously were projected on opposite sides of a tank, and researchers measured the time the female spent with each animation. While younger and smaller females still showed a preference for the symmetrical male, older and larger females increasingly preferred the asymmetrical male.

In previous research conducted elsewhere, females were shown to prefer symmetrical over asymmetrical males when presented with a choice. Scientists suggested that symmetrical figures have more redundant information, which makes for a more powerful, easy-to-remember stimulus. Females also may be likely to choose symmetrical males because they are better able to deal with environmental stresses and could pass on that resilience to offspring.

Another explanation would be that the visual system “develops an internal prototype of an object that is based on an average of all the male fish [the females] have seen,” Morris said. “Therefore, any fish they see that is closest to this prototype is preferred.” The same phenomenon has been suggested to explain attraction in other animals, including humans.

As their lives progress, however, female swordtails may encounter more asymmetrical than symmetrical males, and so begin to prefer the pattern to which they have become accustomed in their environment, she said.

Further research based on this study might examine whether the experience of mating draws older females to asymmetrical males, or whether there is a genetic factor, activated at a certain age or size, that makes larger females select more asymmetrically striped males.

The asymmetrical barring pattern is likely a result of environmental stresses experienced before birth, Morris explained. Some males have the genetic makeup to deal with these stresses and still develop a symmetrical pattern, while others survive the stress but show marks of the struggle. A population with a large amount of asymmetrical individuals may have been subject to a lot of environmental stress, such as pollution.

Co-authors of the study were post-doctoral fellow Oscar Rios-Cardenas and undergraduate student Mary Scarlett Tudor, both of Ohio University.


Story Source:

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


Cite This Page:

Ohio University. "Older Female Fish Prefer Imperfect Male Mates, Study Finds." ScienceDaily. ScienceDaily, 15 November 2005. <www.sciencedaily.com/releases/2005/11/051115170530.htm>.
Ohio University. (2005, November 15). Older Female Fish Prefer Imperfect Male Mates, Study Finds. ScienceDaily. Retrieved August 30, 2014 from www.sciencedaily.com/releases/2005/11/051115170530.htm
Ohio University. "Older Female Fish Prefer Imperfect Male Mates, Study Finds." ScienceDaily. www.sciencedaily.com/releases/2005/11/051115170530.htm (accessed August 30, 2014).

Share This




More Plants & Animals News

Saturday, August 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Killer Amoeba Found in Louisiana Water System

Killer Amoeba Found in Louisiana Water System

AP (Aug. 28, 2014) State health officials say testing has confirmed the presence of a killer amoeba in a water system serving three St. John the Baptist Parish towns. (Aug. 28) Video provided by AP
Powered by NewsLook.com
Raw: Australian Sheep Gets Long Overdue Haircut

Raw: Australian Sheep Gets Long Overdue Haircut

AP (Aug. 28, 2014) Hoping to break the record for world's wooliest, Shaun the sheep came up 10 pounds shy with his fleece weighing over 50 pounds after being shorn for the first time in years. (Aug. 28) Video provided by AP
Powered by NewsLook.com
Minds Blown: Scientists Develop Fish That Walk On Land

Minds Blown: Scientists Develop Fish That Walk On Land

Newsy (Aug. 28, 2014) Canadian scientists looking into the very first land animals took a fish out of water and forced it to walk. Video provided by Newsy
Powered by NewsLook.com
Huge Ancient Wine Cellar Found In Israel

Huge Ancient Wine Cellar Found In Israel

Newsy (Aug. 28, 2014) An international team uncovered a large ancient wine celler that likely belonged to a Cannonite ruler. 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:
from the past week

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