Featured Research

from universities, journals, and other organizations

Reversible Bone Shrinkage Documented In Galapagos Iguanas

Date:
January 10, 2000
Source:
University Of Illinois At Urbana-Champaign
Summary:
Measurements showing vertebrate animals getting smaller during the course of a study normally are dismissed as measurement error or not possible. Eighteen years of data from the Galapagos Islands, however, indicate such shrinkage is both occurring and reversible.

CHAMPAIGN, Ill. -- Measurements showing vertebrate animals getting smaller during the course of a study normally are dismissed as measurement error or not possible. Eighteen years of data from the Galapagos Islands, however, indicate such shrinkage is both occurring and reversible.

In the Jan. 6 issue of the journal Nature, scientists studying marine iguanas of two island populations report that the herbivorous reptiles shrank as much as 6.8 centimeters (2.7 inches) -- up to 20 percent of body length -- in two-year time spans. The iguanas (Amblyrhynchus cristatus) were shrinking, the scientists report, to boost their survival during a change in the weather.

Shrinkage was noted in 1982-83, 1987-88, 1992-93 and 1997-98. The measurements were noted and dismissed, but a pattern was soon discovered: Each of the shrinking periods came in El Niño years.

“In 1997-98, the animals had shrunk too much to ignore,” said Martin Wikelski, a professor of ecology, ethology and evolution at the University of Illinois. “We thought that this couldn’t be an artifact, so we plotted out the data. It turned out to be very interesting.”

The iguanas eat algae along the tidal basins of the rocky shores of the Galapagos archipelago off Ecuador. The islands normally experience cold, nutrient-rich currents from both the west and south. During El Niño years, however, warm currents and heavy rains raise water temperatures. Less digestible brown algae replaces the iguanas’ preferred green and red algae.

In years immediately after El Niño events, surviving iguanas ate well and got fat, then started growing longer again, Wikelski said. For instance, 600 iguanas were measured and marked in 1992. Following the subsequent El Niño, they were monitored. The larger iguanas -- those more than 300 millimeters (11.7 inches) from snout to anus -- shrank the most and survived the longest.

“In shrinking, they also get slimmer, and their mouths get smaller, making them more efficient at harvesting the tiny amounts of available algae,” Wikelski said. “They shrink to reach a body size where survival is high. If they shrank a centimeter or so, they already increased their survival rate by 10 percent. If they shrink more, they can increase survivability by 35 percent.”

Wikelski and co-author Corinna Thom, a biologist at the University of Wurzburg in Germany, theorize that bone absorption accounts for much of the shrinkage, because a reduction of connective tissues between the bones cannot account for it, and that high levels of corticosterone may be involved.

Perhaps as interesting to the bone shrinkage is the renewed growth of bone. Humans suffering from osteoporosis as a result of aging or space flight are unable to recover from the loss of bone length and density, especially losses in long bones.

“We are looking for the mechanism,” Wikelski said. “Is it a certain hormone or combination of hormones, or is it some other physiological mechanism that tells bone to regrow and recalcify? I think these findings are potentially important for all kinds of vertebrates.”


Story Source:

The above story is based on materials provided by University Of Illinois At Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University Of Illinois At Urbana-Champaign. "Reversible Bone Shrinkage Documented In Galapagos Iguanas." ScienceDaily. ScienceDaily, 10 January 2000. <www.sciencedaily.com/releases/2000/01/000110071021.htm>.
University Of Illinois At Urbana-Champaign. (2000, January 10). Reversible Bone Shrinkage Documented In Galapagos Iguanas. ScienceDaily. Retrieved August 2, 2014 from www.sciencedaily.com/releases/2000/01/000110071021.htm
University Of Illinois At Urbana-Champaign. "Reversible Bone Shrinkage Documented In Galapagos Iguanas." ScienceDaily. www.sciencedaily.com/releases/2000/01/000110071021.htm (accessed August 2, 2014).

Share This




More Plants & Animals News

Saturday, August 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Pyrenees Orphan Bear Cub Gets Brand New Home

Pyrenees Orphan Bear Cub Gets Brand New Home

AFP (Aug. 1, 2014) — The discovery of a bear cub in the Pyrenees mountains made headlines in April 2014. Despire several attempts to find the animal's mother, the cub remained alone. Now, the Pyrenees Conservation Foundation has constructed an enclosure. Duration: 00:31 Video provided by AFP
Powered by NewsLook.com
Ebola Vaccine Might Be Coming, But Where's It Been?

Ebola Vaccine Might Be Coming, But Where's It Been?

Newsy (Aug. 1, 2014) — Health officials are working to fast-track a vaccine — the West-African Ebola outbreak has killed more than 700. But why didn't we already have one? Video provided by Newsy
Powered by NewsLook.com
Study Links Certain Birth Control Pills To Breast Cancer

Study Links Certain Birth Control Pills To Breast Cancer

Newsy (Aug. 1, 2014) — Previous studies have made the link between birth control and breast cancer, but the latest makes the link to high-estrogen oral contraceptives. Video provided by Newsy
Powered by NewsLook.com
Rare Whale Fossil Pulled from Calif. Backyard

Rare Whale Fossil Pulled from Calif. Backyard

AP (Aug. 1, 2014) — A rare whale fossil has been pulled from a Southern California backyard. The 16- to 17-million-year-old baleen whale fossil is one of about 20 baleen whale fossils known to exist. (Aug. 1) 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