Featured Research

from universities, journals, and other organizations

When To Reproduce? It's All In The Timing

Date:
February 20, 1998
Source:
University Of Maine
Summary:
Timing is everything, as lovers know. Susan Brawley, a University of Maine marine biologist, leads a research team which has used that truth, along with the results of biochemical studies with seaweed, to overturn a widely-held principle of reproduction in aquatic organisms.

Timing is everything, as lovers know. Susan Brawley, a University of Maine marine biologist, leads a research team which has used that truth, along with the results of biochemical studies with seaweed, to overturn a widely-held principle of reproduction in aquatic organisms.

Their work demonstrates a heretofore unknown biochemical mechanism which makes organisms "exquisitely sensitive" to environmental cues such as water motion and salinity, according to a 1996 paper co-authored by Brawley and her research team.

Brawley gave a presentation today about her team's work at the annual meeting of the American Association for the Advancement of Science in Philadelphia.

The organisms in question are those which reproduce in the water by external fertilization -- some species of fish, corals, and plants such as seaweeds. The results of previous experiments and modeling studies have concluded that, when it comes to fertilization, these organisms don't have that knack for good timing, i.e., that their rate of fertilization success borders on one percent or less.

These studies have used an underlying assumption that reproductive cells, or gametes, are released when water is turbulent. As a result, gametes would be diluted and dispersed. Few would find their target under such conditions.

In light of the evolutionary success of seaweeds and other organisms which use external fertilization, this line of reasoning struck Brawley as odd. "Selection pressure should act quickly on any characteristic that allows an organism to have fertilization success," she says. The hypothesis of an extremely low success rate doesn't meet this evolutionary test.

Isle of Man

During a 1990 sabbatical on the Isle of Man, Brawley became interested in Fucus , a globally common family of brown seaweeds. Fucus species were the only seaweed known to thrive equally well in saline waters as well as low salinity environments such as the Baltic Sea.

In following years, she received support from the National Science Foundation for field studies and laboratory experiments to find out how Fucus adapted to such different chemical conditions. Her primary concern was the mechanism which allowed Fucus to avoid polyspermy, a lethal condition in which an egg is fertilized by more than one sperm. Seaweeds normally depend on high concentrations of sodium to prevent polyspermy, but the Baltic Sea populations didn't have much sodium to work with.

Brawley worked closely on this question with researchers at the University of Stockholm and University of Umeε in Sweden. During her work, she also noticed that Fucus vesiculosis didn't release its gametes until slack high tide. She suspected that the plants were responding to water motion and, perhaps, to accompanying changes in salinity.

Back at the University of Maine in Orono, Brawley worked with Gareth Pearson, a post-doctoral researcher, and Esther Serrao, a graduate student, to study this possibility in earnest. They used Baltic specimens Brawley had brought from Scandinavia, and they collected plants from tide pools along the Maine coast. They also received plants from researchers in California.

"We were able to simulate in the laboratory that high salinity is one of the cues for the release of gametes, and all of that was done under calm conditions," says Brawley. "In the back of my mind, I kept thinking about the affect of water motion. Nearly every introductory biology book you read will have some statement that organisms that use external fertilization have to release lots and lots of gametes because fertilization success is low.

"Now with five different fucoid algae in California, the Baltic and here in Maine, we've found that the adults were waiting to release their gametes under conditions that were less turbulent. When the gametes aren't diluted, fertilization success is high. I think that's going to stand in most cases."

Carbon is the key

In a subsequent series of experiments, Brawley, Pearson and Serrao delved into the biochemical mechanism underlying gamete release. Levels of dissolved inorganic carbon such as carbon dioxide and bicarbonate, they hypothesized, might provide a key.

While the sun is shining, plants take up carbon as they carry out photosynthesis. Brawley and her team reasoned that when water is being churned by waves or tidal currents, the plants are constantly receiving new supplies of carbon. Gametes are not released under such circumstances.

That changes, however, when the water is calm. Without turbulence, the carbon supply begins to run out. The UMaine experiments have shown that the carbon deficit is the chemical signal for plants to release their gametes. It is the green light which tells the plants that the water is calm and the time is right for reproduction.

"We did two types of experiments," says Brawley. "One was a series of tests to see what was involved with dissolved inorganic carbon." In those tests, the researchers varied the levels of carbon in the water. They also agitated the water to simulate turbulent conditions. In reach case, the results were consistent with the team's predictions.

"It is a boundary layer disturbance. That's important to show. Many cells have a mechanical response to pushing, bending, something like that, but this is chemical sensing," Brawley says.

"What I expect is that external fertilization is going to be found to be very successful in these organisms. The caveat is that we always have to remember that we're looking at a snapshot of evolution and that not every species is at its heyday. It may be a species that is on its way out, or it may be one that is recent. We have to keep in mind where it is relative to selective mechanisms or how well adapted it is to the community it lives in."


Story Source:

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


Cite This Page:

University Of Maine. "When To Reproduce? It's All In The Timing." ScienceDaily. ScienceDaily, 20 February 1998. <www.sciencedaily.com/releases/1998/02/980220064241.htm>.
University Of Maine. (1998, February 20). When To Reproduce? It's All In The Timing. ScienceDaily. Retrieved July 29, 2014 from www.sciencedaily.com/releases/1998/02/980220064241.htm
University Of Maine. "When To Reproduce? It's All In The Timing." ScienceDaily. www.sciencedaily.com/releases/1998/02/980220064241.htm (accessed July 29, 2014).

Share This




More Plants & Animals News

Tuesday, July 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deadly Ebola Virus Threatens West Africa

Deadly Ebola Virus Threatens West Africa

AP (July 28, 2014) — West African nations and international health organizations are working to contain the largest Ebola outbreak in history. It's one of the deadliest diseases known to man, but the CDC says it's unlikely to spread in the U.S. (July 28) Video provided by AP
Powered by NewsLook.com
Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) — Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Newsy (July 28, 2014) — The asteroid that killed the dinosaurs struck at the worst time for them. A new study says that if it hit earlier or later, they might've survived. Video provided by Newsy
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) — A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
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