Featured Research

from universities, journals, and other organizations

Segmentation is the secret behind the extraordinary diversification of animals

Date:
July 27, 2010
Source:
CNRS
Summary:
Segmentation, the repetition of identical anatomical units, seems to be the secret behind the diversity and longevity of the largest and most common animal groups on Earth. Researchers have shown that this characteristic was inherited from a common segmented ancestor thought to have lived 600 million years ago and whose presence "changed the face of the world."

An example of animal with highly-visible repeated anatomical units: a Vietnamese cave centipede
Credit: Copyright CNRS Photothèque / DEHARVENG Louis

Segmentation, the repetition of identical anatomical units, seems to be the secret behind the diversity and longevity of the largest and most common animal groups on Earth. Researchers from CNRS and Université Paris Diderot have shown that this characteristic was inherited from a common segmented ancestor thought to have lived 600 million years ago and whose presence "changed the face of the world."

This discovery is published in Science on 16 July 2010.

What do centipedes, earthworms and humans have in common? They all feature the repetition of anatomically identical units along the axis running from the front to the rear of their bodies. This characteristic, which researchers call segmentation, is shared by three large groups of animals. It may not be obvious at first glance though, as the repeated segments can be hidden by a shell or be partially fused. The segments are nevertheless present, laid out along the bilateral axis in the trunk, abdomen or thorax.

The first of these animal groups is the arthropods, which include centipedes but also insects, spiders, scorpions and crustaceans, representing by far the largest group of animals on the planet. With the highest number of species and individuals, it makes up nearly 40% of animal biomass. Apart from centipedes, whose segmentation is impossible to miss, arthropods also include grasshoppers, crickets and shrimps. Vertebrates, another highly diverse group, come next. They comprise most familiar animals, including humans, and they represent an evolutionary success. In this group, segmentation is found in the vertebrae of the backbone and, at a finer anatomical scale, in the muscles and nerves that spread from the spinal cord. The final group is the annelid worms, whose body is almost entirely formed of identical segments, such as sea and earthworms. They are also very numerous in terms of species, though much less conspicuous.

These three groups are not closely related to one another. So, where does their segmentation come from? Is it possible that they all inherited this feature from a very distant common ancestor that lived 600 million years ago, before the Cambrian explosion, which produced most of the large animal groups that exist today? Or has segmentation occurred several times during the history of evolution? This is the question addressed by the researchers of CNRS and Université Paris Diderot at the Institut Jacques Monod, because segments seem to offer a significant advantage to the groups that have them, in terms of diversity, longevity and overall evolutionary success.

The researchers found that the genes controlling segment formation during embryo development are almost the same in drosophila (an arthropod) and in annelid marine worms, on which they concentrated their studies. These similarities led them to conclude that the genes had been inherited from a common ancestor, which was itself segmented. It also appears that vertebrates inherited this characteristic from an ancestor they share with the arthopods and the annelids. This is what the researchers are now seeking to confirm.

This work supports the idea that segmentation only appeared once in the history of evolution and that it led to the broad diversity of animal groups possessing it. This old and controversial idea among zoologists, had never been proved until now. But why should segmentation be so advantageous? Over millions of years, and exposure to changing environmental constraints, it is easier for an animal to specialize a segment into a specific tool in response to a need, than to create a whole new organ from scratch. By chance, evolution may have played a winning card with segmentation, which profoundly marked the history of life on Earth. If one day we could play God and create artificial animals or even biomimetic robots, perhaps we too should think about it. But this is still within the realm of science fiction.


Story Source:

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


Journal Reference:

  1. Dray et al. Hedgehog Signaling Regulates Segment Formation in the Annelid Platynereis. Science, 2010; 329 (5989): 339 DOI: 10.1126/science.1188913

Cite This Page:

CNRS. "Segmentation is the secret behind the extraordinary diversification of animals." ScienceDaily. ScienceDaily, 27 July 2010. <www.sciencedaily.com/releases/2010/07/100726222316.htm>.
CNRS. (2010, July 27). Segmentation is the secret behind the extraordinary diversification of animals. ScienceDaily. Retrieved September 20, 2014 from www.sciencedaily.com/releases/2010/07/100726222316.htm
CNRS. "Segmentation is the secret behind the extraordinary diversification of animals." ScienceDaily. www.sciencedaily.com/releases/2010/07/100726222316.htm (accessed September 20, 2014).

Share This



More Plants & Animals News

Saturday, September 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Chocolate Museum Opens in Brussels

Chocolate Museum Opens in Brussels

AFP (Sep. 19, 2014) — Considered a "national heritage" in Belgium, chocolate now has a new museum in Brussels. In a former chocolate factory, visitors to the permanent exhibition spaces, workshops and tastings can discover derivatives of the cocoa bean. Duration: 01:00 Video provided by AFP
Powered by NewsLook.com
Could Grief Affect The Immune Systems Of Senior Citizens?

Could Grief Affect The Immune Systems Of Senior Citizens?

Newsy (Sep. 19, 2014) — The study found elderly people are much more likely to become susceptible to infection than younger adults going though a similar situation. Video provided by Newsy
Powered by NewsLook.com
Jury Delivers Verdict in Salmonella Trial

Jury Delivers Verdict in Salmonella Trial

AP (Sep. 19, 2014) — A federal jury has convicted three people in connection with an outbreak of salmonella poisoning five years ago that sickened hundreds of people and was linked to a number of deaths. (Sept. 19) Video provided by AP
Powered by NewsLook.com
Raw: Elephant Undergoes Surgery in Tbilisi Zoo

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

AP (Sep. 18, 2014) — Grand the elephant has successfully undergone surgery to remove a portion of infected tusk at Tbilisi Zoo in Georgia. British veterinary surgeons used an electric drill to extract the infected piece. (Sept. 18) 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