Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study finds surprising new branches on arthropod family tree

11.02.2010
Any way you look at it -- by sheer weight, species diversity or population -- the hard-shelled, joint-legged creepy crawlies called arthropods dominate planet Earth. Because of their success and importance, scientists have been trying for decades to figure out the family relationships that link lobsters to millipedes and cockroaches to tarantulas and find which might have come first.

In a scientific and technological tour de force that was nearly a decade in the making, a team of scientists from Duke University, the University of Maryland and the Natural History Museum of Los Angeles County have compared genetic sequences from 75 different species to draw a new family tree that includes every major arthropod lineage. Some of the relationships are so surprising that new names had to be coined for five newly-discovered groupings.

The work, which was supported by the National Science Foundation, appears early online Wednesday in the journal Nature.

A big surprise to tumble out of the new tree is that the closest living relatives of insects include a small and obscure group of creatures called remipedes that were only discovered in the late 1970s living in a watery cave in the Bahamas. With linear bodies like centipedes, simple legs and no eyes, it was thought that this small group -- now placed with cephalocarids in the newly-named Xenocarida or "strange shrimp" -- would be found at the base of the crustacean family tree.

Now, after analyzing 62 shared genetic sequences across all the arthropods, the researchers are putting the strange shrimp together with the six-legged insects, Hexapoda, to form a new group they dubbed Miracrustacea, or "surprising crustaceans." As a "sister clade" to hexapods, the Xenocarida likely represent the sort of creature that came onto land to start the spectacular flowering of the insect lineage, said Cliff Cunningham, a professor of biology at Duke who led the study.

Triops, a 2-inch crustacean that looks like a cross between a horseshoe crab and a mayfly, had also been thought of as an early crustacean, but it too was shown to have a relatively modern origin in the new analysis, Cunningham said.

"Taxonomists have been arguing about these things for decades, and people kept coming at this with one data set after another," Cunningham said. This latest study has created a fuller picture of the arthropod family tree by using more species and more genes, he said.

Beginning in 2001, Jeffrey Shultz, an associate professor of entomology at Maryland, led the efforts to figure out which species needed to be sequenced for a robust comparison, and then to round up suitable specimens of each. The study included nematodes, scorpions, dragonflies, barnacles, copepods and centipedes.

Remipedes, one of the two species of Xenocarida in the study, had to be fetched from partially submerged limestone caves in the Yucatan Peninsula and preserved just so. Bitty creatures called mystacocarids that live between grains of sand were captured by the Natural History Museum's Regina Wetzer, using a microscope on a Massachusetts beach.

Once assembled, the 75 species were then stripped down to their DNA for a painstaking search to find genetic sequences that would appear across all arthropods, enabling statistical comparisons.

The lab of Jerome Regier at Maryland's Center for Biosystems Research combed through 2,500 different combinations of PCR primers to find 62 protein-coding gene sequences that could be compared across all 75 species. Regier was an early proponent of using protein coding genes to sort out the arthropod tree, while most other researchers were using relatively less complex analyses from the DNA found in ribosomes and mitochondria.

The researchers ran four different statistical approaches, including two new ones invented at Maryland, "and they all came up with the same answer," Cunningham said. Earlier studies had not used as many genes or as many species, making this study about four times larger than anything done previously.

The spiders, ticks and scorpions of the subgroup Chelicerata are shown to have split from the line leading to insects and crustaceans even before the millipedes and centipedes of the subphylum Myriapoda. Most recent molecular studies had grouped these arachnids in Chelicerata together with millipedes and centipedes of the Myriapoda. But the new analysis puts millipedes and centipedes together with crustaceans and insects in a group taxonomists had long ago named Mandibulata.

"The only thing people thought they knew before molecular data was available was that the Myriapods were with the insects," Shultz said. But that turned out to be wrong. Even the grouping Crustacea is no longer correct, since it includes the six-legged insects.

Within the insect group Hexapoda, the good news for taxonomists who have grouped insects according to body shape and features is that they were pretty much on the mark, Shultz added.

There are still many holes that need to be filled in, Cunningham said, but at least the shape of the tree seems right. "Now the developmental biologists can really piece things together."

Karl Leif Bates | EurekAlert!
Further information:
http://www.duke.edu

More articles from Life Sciences:

nachricht Snap, Digest, Respire
20.01.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht Scientists initiate first ethical guidelines for organs cultivated in vitro
20.01.2017 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland

19.01.2017 | Earth Sciences

Not of Divided Mind

19.01.2017 | Life Sciences

Molecule flash mob

19.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>