Featured Research

from universities, journals, and other organizations

Why Don't More Animals Change Their Sex?

Date:
February 4, 2009
Source:
Yale University
Summary:
Most animals, like humans, have separate sexes -- they are born, live out their lives and reproduce as one sex or the other. However, some animals live as one sex in part of their lifetime and then switch to the other sex, a phenomenon called sequential hermaphroditism. What remains a puzzle is why the phenomenon is so rare, since a detailed analysis shows the biological "costs" of changing sexes rarely outweigh the advantages.

Shown clockwise from upper left, the Bluehead wrasse (Thalassoma bifasciatum), Northern shrimp (Pandalus borealis), Common slipper shell (Crepidula fornicate) and Whip coral goby (Bryaninops yongei) are examples of some animals that change their sex.
Credit: Erem Kazancıoğlu

Most animals, like humans, have separate sexes — they are born, live out their lives and reproduce as one sex or the other. However, some animals live as one sex in part of their lifetime and then switch to the other sex, a phenomenon called sequential hermaphroditism. What remains a puzzle, according to Yale scientists, is why the phenomenon is so rare, since their analysis shows the biological "costs" of changing sexes rarely outweigh the advantages.

Related Articles


A report by Yale scientists in the March issue of The American Naturalist says that while this process is evolutionarily favored, its rarity cannot be explained by an analysis of the biological costs vs benefits.

Sequential hermaphroditism naturally occurs in various organisms from plants to fishes. Following four decades of research that established why sex change is advantageous, the question remained why it is rare among animals. In this study, Yale graduate student Erem Kazancıoğlu and his advisor Suzanne Alonzo, assistant professor of ecology and evolutionary biology, demonstrate that sex change is surprisingly robust against costs.

While the adaptive advantage of sex change is well understood, it is not clear why relatively few animals change sex. According to Alonzo, "An intuitive, yet rarely studied, explanation is that the considerable time or energy it takes to change sex make hermaphroditism unfeasible for most animals."

To test whether the biological costs of changing sex affect sex change actually occurs, the researchers built theoretical models of the hermaphrodite and separate-sex life histories. In their "game" models, sex change "players" vary the age of their sex change, while the separate-sex strategy responds by altering the number of male and female offspring it produces.

"We were surprised to see that a hermaphrodite could spend 30 percent of its lifetime in the process of change sex, and still persist in a population," said Kazancıoğlu. "This suggests that only huge costs can disfavor sex change."

So, why is sex change so rare? And, why does one species of fish reproduce strictly as separate sexes, while another very closely related species flexibly changes sex? A comparative study of hermaphroditic and separate-sex mating systems, which the authors are currently performing, may provide a clue, according to Kazancıoğlu, "Reproductive behaviors such as parental care seem to disfavor sex change in some species. We are investigating whether general patterns like these may explain the rarity of hermaphroditism."

Yale University and the National Science Foundation funded the research.


Story Source:

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


Cite This Page:

Yale University. "Why Don't More Animals Change Their Sex?." ScienceDaily. ScienceDaily, 4 February 2009. <www.sciencedaily.com/releases/2009/02/090203110326.htm>.
Yale University. (2009, February 4). Why Don't More Animals Change Their Sex?. ScienceDaily. Retrieved March 31, 2015 from www.sciencedaily.com/releases/2009/02/090203110326.htm
Yale University. "Why Don't More Animals Change Their Sex?." ScienceDaily. www.sciencedaily.com/releases/2009/02/090203110326.htm (accessed March 31, 2015).

Share This


More From ScienceDaily



More Plants & Animals News

Tuesday, March 31, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Bionic Ants Could Be Tomorrow's Factory Workers

Bionic Ants Could Be Tomorrow's Factory Workers

Reuters - Innovations Video Online (Mar. 30, 2015) Industrious 3D printed bionic ants working together could toil in the factories of the future, says German technology company Festo. The robotic insects cooperate and coordinate their actions and movements to achieve a common aim. Amy Pollock reports. Video provided by Reuters
Powered by NewsLook.com
Captive-Born Panda Triplets Are Eight Months Old

Captive-Born Panda Triplets Are Eight Months Old

Reuters - Light News Video Online (Mar. 30, 2015) The world&apos;s only surviving captivity-born panda triplets turn eight months old, according to China’s state media. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Lions Make Surprise Comeback in Gabon

Lions Make Surprise Comeback in Gabon

AFP (Mar. 30, 2015) Lions have made a comeback in southeast Gabon, after disappearing for years, according to live footage from US wildlife organisation Panthera. Duration: 00:32 Video provided by AFP
Powered by NewsLook.com
Ancient Egyptian Beer Making Vessels Discovered in Israel

Ancient Egyptian Beer Making Vessels Discovered in Israel

AFP (Mar. 30, 2015) Fragments of pottery used by Egyptians to make beer and dating back 5,000 years have been discovered on a building site in Tel Aviv, the Israeli Antiquities Authority said on Sunday. Duration: 00:51 Video provided by AFP
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


Plants & Animals

Earth & Climate

Fossils & Ruins

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