Featured Research

from universities, journals, and other organizations

First Evolutionary Branching For Bilateral Animals Found

Date:
September 25, 2009
Source:
Brown University
Summary:
In the most computationally intensive phylogenetic analysis to date, an international research team has found the first evolutionary branching for bilateral animals. The researchers determined that the flatworm group Acoelomorpha is a product of the deepest split within the bilateral creatures -- multi-celled organisms that, like humans, have symmetrical body forms.

Flatworm with a home: An international research team led by Brown University has determined that the flatworm Acoelomorpha belongs as a sister clade to other bilateral animals. The finding means the worm is a product of the deepest split within the bilateral animals, the first evolutionary divergence within the group.
Credit: Eric Rottinger/Kahikai.org

When it comes to understanding a critical junction in animal evolution, some short, simple flatworms have been a real thorn in scientists’ sides. Specialists have jousted over the proper taxonomic placement of a group of worms called Acoelomorpha. This collection of worms, which comprises roughly 350 species, is part of a much larger group called bilateral animals, organisms that have symmetrical body forms, including humans, insects and worms. The question about acoelomorpha, was: Where do they fit in?

To scientists, acoelomorpha, has been enigmatic, a “rogue animal,” said Casey Dunn, an evolutionary biologist at Brown University. “It has been wandering throughout the animal tree of life.”

The worm wanders no more. Through a laborious genetic sequencing analysis, Dunn and an international team of scientists have settled the long-standing debate and determined that acoelomorpha belongs as a sister clade to other bilateral animals. The finding is significant, Dunn said, because it shows the worm is a product of the deepest split within the bilateral animals, the first evolutionary divergence within the group. Because of that, scientists have gained a key insight into the most recent common ancestor to bilaterians, a species that remains unknown.

The worm is “as distant as an animal can be in bilateria and still be a bilaterian,” said Dunn, assistant professor of biology. “So, now we have two perspectives to (find out about) this common ancestor, the acoelomorphs and all the other bilateral animals.”

The results appear online this week in the Proceedings of the Royal Society B.

The team, composed of 17 scientists from the United States, France Germany, Sweden, Spain and the United Kingdom, had two more interesting findings:

  • The debate appears to be over for Xenoturbella, a type of marine worm whose ancestral affiliation had been tossed between worms and mollusks. The researchers reported their genetic analysis shows diminishing evidence for placing xenoturbella within Deuterostomia, one of the major groups within the animal kingdom. Coincidentally, it also shows that xenoturbella may be a close relative to acoelomorpha.
  • Cycliophora, a single species discovered in 1994 that lives on the bristles surrounding the mouth of the Norway lobster Nephrops norvegicus, has found a home with Entoprocta and Ectoprocta. The researchers base their findings on an analysis that reached further into the genetic makeup of cycliophora than previous studies had done.

The team used a genetic sequencing technique called expressed sequence tags to carry out the phylogenetic studies. The aim of this approach, discusssed in a study led by Dunn that appeared in Nature last year, is to analyze a large number of genes from a large number of animals. For this paper, the researchers looked at 1,487 genes, a 10-fold increase in the number of genes analyzed in previous studies. In all, the researchers logged 2.25 million processor hours on a supercomputer in California to obtain the results. Dunn called the effort the most computationally intensive phylogenetic analysis to date.

Other scientists who contributed to the research are Andreas Hejnol, Mark Martindale and Elaine Seaver, University of Hawaii; Matthias Obst, Goteborg University, Sweden; Alexandros Stamatakis and Michael Ott, Technical University of Munich, Germany; Greg Rouse, Scripps Institution of Oceanography; Gregory Edgecombe, Natural History Museum, London; Pedro Martinez and Jaume Baguna, Universitat de Barcelona, Spain; Xavier Bailly, Station Biologique de Roscoff, France; Ulf Jondelius, Swedish Museum of Natural History; Matthias Wiens and Werner Muller, Johannes-Gutenberg-University Mainz, Germany; Ward Wheeler, American Museum of Natural History; and Gonzalo Giribet, Harvard University.

The research was funded by the National Science Foundation and the San Diego Supercomputing Center.


Story Source:

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


Journal Reference:

  1. Andreas Hejnol, Matthias Obst, Alexandros Stamatakis, Michael Ott, Greg W. Rouse, Gregory D. Edgecombe, Pedro Martinez, Jaume Baguρΰ, Xavier Bailly, Ulf Jondelius, Matthias Wiens, Werner E. G. Mόller, Elaine Seaver, Ward C. Wheeler, Mark Q. Martindale, Gonzalo Giribet, and Casey W. Dunn. Assessing the root of bilaterian animals with scalable phylogenomic methods. Proceedings of The Royal Society B Biological Sciences, 2009; DOI: 10.1098/rspb.2009.0896

Cite This Page:

Brown University. "First Evolutionary Branching For Bilateral Animals Found." ScienceDaily. ScienceDaily, 25 September 2009. <www.sciencedaily.com/releases/2009/09/090923112543.htm>.
Brown University. (2009, September 25). First Evolutionary Branching For Bilateral Animals Found. ScienceDaily. Retrieved April 17, 2014 from www.sciencedaily.com/releases/2009/09/090923112543.htm
Brown University. "First Evolutionary Branching For Bilateral Animals Found." ScienceDaily. www.sciencedaily.com/releases/2009/09/090923112543.htm (accessed April 17, 2014).

Share This



More Plants & Animals News

Thursday, April 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Change of Diet Helps Crocodile Business

Change of Diet Helps Crocodile Business

Reuters - Business Video Online (Apr. 16, 2014) — Crocodile farming has been a challenge in Zimbabwe in recent years do the economic collapse and the financial crisis. But as Ciara Sutton reports one of Europe's biggest suppliers of skins to the luxury market has come up with an unusual survival strategy - vegetarian food. Video provided by Reuters
Powered by NewsLook.com
Could Even Casual Marijuana Use Alter Your Brain?

Could Even Casual Marijuana Use Alter Your Brain?

Newsy (Apr. 16, 2014) — A new study conducted by researchers at Northwestern and Harvard suggests even casual marijuana use can alter your brain. Video provided by Newsy
Powered by NewsLook.com
Thousands Of Vials Of SARS Virus Go Missing

Thousands Of Vials Of SARS Virus Go Missing

Newsy (Apr. 16, 2014) — A research institute in Paris somehow misplaced more than 2,000 vials of the deadly SARS virus. Video provided by Newsy
Powered by NewsLook.com
Raw: Three Rare White Tiger Cubs Debut at Zoo

Raw: Three Rare White Tiger Cubs Debut at Zoo

AP (Apr. 16, 2014) — The Buenos Aires Zoo debuted a trio of rare white Bengal tiger cubs on Wednesday. (April 16) 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