Most animals, like humans, have separate sexes. We are born, live out our lives and reproduce as one sex or the other, but some animals live as one sex in part of their lifetime and then switch to the other sex, a phenomenon called sequential hermaphroditism. Yale scientists believe the bigger puzzle is why the phenomenon is so rare, since their analysis shows the biological “costs” of changing sexes rarely outweigh the advantages.
This process is even evolutionarily favored, they say, so 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 Kazancioglu 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 Kazancioglu. “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 Kazancioglu, “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.
Citation: The American Naturalist (March 2008)
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Part I: Bee Deaths Mystery Solved? Neonicotinoids (Neonics) May Actually Help Bee Health
- Chronic Pain Isn't All In The Brain
- Smoking, Drinking And Eating: It's Not About Your Freedom
- Violence, Sex And Taboo: The Original Brothers Grimm Fairy Tales Back In Print
- Part II: Bee Deaths And CCD - Flawed Chensheng Lu Harvard Studies Endanger Bees
- On integrating out short-distance physics
- Is The Micropower Revolution Here?
- "There is no question they were created to cater to universities and are staffed by people from..."
- "And my second link should be not a copy of the first, but this: http://www.nature.com/news/half..."
- "Recently I saw The Conversation remove/censor legitimate comments arguing against an article written..."
- tags because there's no testing..." href="/robert_inventor/why_we_cant_backup_earth_on_mars_the_moon_or_anywhere_else_in_our_solar_system-148364#comment-182183">"Robert, you might want to reformat my post. I intended to highlight only the headlines for easy..."
- "My only complaint with good thinkers and writers has hither always been that they should produce..."
Books By Writers Here