Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fish evolve a longer lifespan by evolving a longer reproductive period, researchers find

28.12.2005


Fish have menopause, study determines; menopausal period not affected by evolution

A UC Riverside-led research team has found that as some populations of an organism evolve a longer lifespan, they do so by increasing only that segment of the lifespan that contributes to "fitness" – the relative ability of an individual to contribute offspring to the next generation.

Focusing on guppies, small fresh-water fish biologists have studied for long, the researchers found that guppies living in environments with a large number of predators have adapted to reproduce earlier in life than guppies from low-predation localities. Moreover, when reproduction ceases, guppies from high-predation localities are far older, on average, than guppies from low-predation localities, indicating that high-predation guppies enjoy a long "reproductive period" – the time between first and last reproduction.



"In earlier work, we showed that guppies from high predation environments have longer lifespans," said David Reznick, professor of biology. "Our new study explores how and why this happens. We found that fish from populations enjoying longer lifespans live longer because there is a selective increase in their reproductive lifespan. Indeed, theory predicts this result because only reproductive lifespan determines fitness."

Study results appear Dec. 27 in the online edition of the Public Library of Science – Biology.

The study supports the controversial hypothesis that natural selection – the process in nature by which only organisms best adapted to their environment tend to survive and pass on their genetic characters in increasing numbers to succeeding generations – introduces changes in only a specific segment of an organism’s lifespan.

The researchers conducted their experiments by comparing life-history traits in 240 guppies they retrieved from high- and low-predation streams in mountains in Trinidad. In their analysis, they divided the life history into three non-overlapping segments: the age at maturity (birth to first reproduction), the reproductive lifespan (first to last reproduction) and the post-reproductive lifespan (last reproduction to death). They also devised a statistical criterion for evaluating whether or not guppies had a post-reproductive lifespan, that is, did guppies live significantly past the end of their capacity to reproduce?

"We were exploring whether or not fish have the equivalent of mammalian menopause," Reznick said. "We found that 60 percent of the fish had a significant post-reproductive lifespan, indicating that, yes, fish do have menopause. Indeed, their patterns of growing old are similar to those of mammals."

The researchers’ statistical analysis also showed that regardless of which environments the guppies lived in, there were no differences among their populations in the probability of having a post-reproductive lifespan or in its duration.

"This is just what one might predict because these fish provide no care for their young," explained Reznick. "The older fish, after they stop reproducing, do not contribute to the fitness of young fish. As a result, the post-reproductive period is not influenced by natural selection. This result could be of interest to those who study menopause in humans and who have argued that post-reproductive humans can increase their own fitness by contributing to the fitness of their grandchildren and that the prolonged post-reproductive lifespan of humans is, therefore, the product of natural selection.

"But such arguments are difficult to prove by working on a single population or species. Nevertheless, our results show how it would be possible to evaluate whether or not menopause in humans has been shaped by natural selection. Appropriate comparisons, such as those between humans and apes, would help."

Iqbal Pittalwala | EurekAlert!
Further information:
http://www.ucr.edu

More articles from Studies and Analyses:

nachricht The Great Unknown: Risk-Taking Behavior in Adolescents
19.01.2017 | Max-Planck-Institut für Bildungsforschung

nachricht A sudden drop in outdoor temperature increases the risk of respiratory infections
11.01.2017 | University of Gothenburg

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>