Featured Research

from universities, journals, and other organizations

Manatee Bones Lead To New Insight On Evolution

Date:
August 31, 2006
Source:
Stanford University Medical Center
Summary:
A new study suggests that mutations in the same gene may be responsible for the evolution of leglessness in animals as distantly related as 1,000-pound manatees and fish smaller than an index finger.

West Indian Manatee.
Credit: U.S. Fish and Wildlife Service

Most research professors spend their days writing grants, teaching and managing graduate students, so when Stanford's David Kingsley, PhD, ventured from his office to his lab, pulled out a scale and started weighing 114 pairs of manatee pelvic bones, it was a sign that something was afoot.

The results of Kingsley's efforts make his departure from the routine worthwhile. He found that in almost every case, the left pelvic bone outweighed the right. Although seemingly trivial in difference--the average left pelvic bone is a mere10 percent larger than its right-side partner--that difference carries big weight in evolutionary significance. It suggests that mutations in the same gene may be responsible for the evolution of leglessness in animals as distantly related as 1,000-pound manatees in Florida and fish smaller than an index finger living in lakes and streams around the world.

"It's striking that evolution might use the same mechanism over and over," said Kingsley, professor of developmental biology at the Stanford University School of Medicine and a Howard Hughes Medical Institute investigator. His study appears in the Aug. 28 online issue of the Proceedings of the National Academy of Sciences.

The reason the asymmetric pelvic bones are important goes back to work Kingsley published in 2004. In that paper, Kingsley's lab showed that mutations in a gene called PitX1 were responsible for the loss of pelvic fins in three different species of a fish called the threespine stickleback. In each of the species, the mutation arose independently as the fish evolved in lakes or streams where a more streamlined shape held some evolutionary advantage.

At the time, Kingsley's work was the first to show that a single gene could be responsible for a large evolutionary change, such as the loss of an entire set of fins, in natural populations. What was particularly interesting was that the mutation arose independently in populations separated by thousands of miles. Mouse researchers had also known that a PitX1 mutation eliminated hind limbs in mice, albeit under artificial conditions. What's more, in both mice and sticklebacks with a PitX1 mutation, the residual pelvis tended to be larger on the left than the right.

That finding is what started Kingsley thinking about manatees -- large, ocean-going mammals -- as well as whales, snakes and skinks, all of which evolved from four-legged ancestors. He theorized that if a PitX1 mutation was responsible for pelvic reductions in several species of sticklebacks and had a similar role in laboratory mice, it might be a mutation used widely by evolution.

As luck would have it, Kingsley made contact with Sentiel Rommel, PhD, a manatee researcher from the Florida Fish and Wildlife Research Institute, who had collected pelvic bones from manatees during autopsies. Kingsley convinced Rommel to send the collection of bones, each about the size of a child's fist. When Kingsley weighed the rudimentary bones, he found that manatees showed the same characteristic asymmetry found in mice and sticklebacks.

The asymmetry observed in manatee pelvic bones suggests that PitX1 may have been used repeatedly as animals evolved from their four-legged ancestors. However, as Kingsley noted, further studies are now needed to pinpoint the DNA changes in Pitx1 or other genes that are associated with pelvic reduction in manatees and other organisms. Although he has no genetic evidence of a PitX1 mutation in manatees, he's trying to strengthen his case by extending his asymmetry observations to other animals. Unfortunately, he has yet to find a cache of snake or whale pelvises.

Still, Kingsley is heartened by the morphological similarities his team has observed between pelvic reduction in very different animals. "It'sencouraging because it means that if you are looking at the genetic mechanisms of evolution in one animal, your results may turn out to be surprisingly general," hesaid.

In this same paper, Kingsley and postdoctoral scholar Michael Shapiro, PhD, show evidence that distantly related species of ninespine sticklebacks, in addition to their threespine cousins, evolved their sleeker shape with help from a PitX1 mutation.

This work was funded by the Helen Hay Whitney Foundation, the Burroughs Wellcome Fund and the National Institutes of Health.


Story Source:

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


Cite This Page:

Stanford University Medical Center. "Manatee Bones Lead To New Insight On Evolution." ScienceDaily. ScienceDaily, 31 August 2006. <www.sciencedaily.com/releases/2006/08/060830213820.htm>.
Stanford University Medical Center. (2006, August 31). Manatee Bones Lead To New Insight On Evolution. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2006/08/060830213820.htm
Stanford University Medical Center. "Manatee Bones Lead To New Insight On Evolution." ScienceDaily. www.sciencedaily.com/releases/2006/08/060830213820.htm (accessed July 25, 2014).

Share This




More Fossils & Ruins News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Mobile App Gives Tour of Battle of Atlanta Sites

Mobile App Gives Tour of Battle of Atlanta Sites

AP (July 25, 2014) Emory University's Center for Digital Scholarship has launched a self-guided mobile tour app to coincide with the 150th anniversary of the Civil War's Battle of Atlanta. (July 25) Video provided by AP
Powered by NewsLook.com
Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Newsy (July 24, 2014) A new study claims a set of prehistoric T-Rex footprints supports the theory that the giant predators hunted in packs instead of alone. Video provided by Newsy
Powered by NewsLook.com
Mint Gives JFK Coin a Face-Lift

Mint Gives JFK Coin a Face-Lift

AP (July 24, 2014) The U.S. Mint has re-designed the John F. Kennedy half dollar coin to better match the former president's likeness. (July 24) Video provided by AP
Powered by NewsLook.com
Raw: MD Church Built in 1773 Ravaged by Fire

Raw: MD Church Built in 1773 Ravaged by Fire

AP (July 22, 2014) Authorities say a 241-year-old church on the National Register of Historic Places has been ravaged by fire in Maryland. (July 22) 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