Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Origin of the unique ventilatory apparatus of turtles

10.11.2014

How the tortoise's ribs got embedded in its shell

Through the careful study of modern and early fossil tortoise, researchers now have a better understanding of how tortoises breathe and the evolutionary processes that helped shape their unique breathing apparatus and tortoise shell.


A Computed Tomography rendering of a snapping turtle (Chelydra serpentina) showing the skeleton (white), lungs (blue), and abdominal muscles (red and pink) used to ventilate the lungs. Because turtles have locked their ribs up into the iconic turtle shell, they can no longer use their ribs to breathe as in most other animals and instead have developed a unique abdominal muscle based system.

Credit: Emma R. Schachner

The findings published in a paper, titled: Origin of the unique ventilatory apparatus of turtles, in the scientific journal, Nature Communications, on Friday, 7 November 2014, help determine when and how the unique breathing apparatus of tortoises evolved.

Lead author Dr Tyler Lyson of Wits University's Evolutionary Studies Institute, the Smithsonian Institution and the Denver Museum of Nature and Science said: "Tortoises have a bizarre body plan and one of the more puzzling aspects to this body plan is the fact that tortoises have locked their ribs up into the iconic tortoise shell. No other animal does this and the likely reason is that ribs play such an important role in breathing in most animals including mammals, birds, crocodilians, and lizards."

Instead tortoises have developed a unique abdominal muscular sling that wraps around their lungs and organs to help them breathe. When and how this mechanism evolved has been unknown.

"It seemed pretty clear that the tortoise shell and breathing mechanism evolved in tandem, but which happened first? It's a bit of the chicken or the egg causality dilemma," Lyson said. By studying the anatomy and thin sections (also known as histology), Lyson and his colleagues have shown that the modern tortoise breathing apparatus was already in place in the earliest fossil tortoise, an animal known as Eunotosaurus africanus.

This animal lived in South Africa 260 million years ago and shares many unique features with modern day tortoises, but lacked a shell. A recognisable tortoise shell does not appear for another 50 million years.

Lyson said Eunotosaurus bridges the morphological gap between the early reptile body plan and the highly modified body plan of living tortoises, making it the Archaeopteryx of turtles.

"Named in 1892, Eunotosaurus is one of the earliest tortoise ancestors and is known from early rocks near Beaufort West," said Professor Bruce Rubidge, Director of the Evolutionary Studies Institute at Wits University and co-author of the paper.

"There are some 50 specimen of Eunotosaurus. The rocks of the Karoo are remarkable in the diversity of fossils of early tortoises they have produced. The fact that we find Eunotosaurus at the base of the Karoo succession strongly suggest that there are more ancestral forms of tortoises still to be discovered in the Karoo," Rubidge added.

The study suggests that early in the evolution of the tortoise body plan a gradual increase in body wall rigidity produced a division of function between the ribs and abdominal respiratory muscles. As the ribs broadened and stiffened the torso, they became less effective for breathing which caused the abdominal muscles to become specialised for breathing, which in turn freed up the ribs to eventually - approximately 50 million years later - to become fully integrated into the characteristic tortoise shell.

Lyson and his colleagues now plan to investigate reasons why the ribs of early tortoises starting to broaden in the first place. "Broadened ribs are the first step in the general increase in body wall rigidity of early basal tortoises, which ultimately leads to both the evolution of the tortoise shell and this unique way of breathing. We plan to study this key aspect to get a better understanding why the ribs started to broaden."

Media enquiries:

Professor Bruce Rubidge is currently undertaking field work in the Karoo. He has intermittent communication access and can be reached on bruce.rubidge@wits.ac.za.

Dr Tyler Lyson is in Germany and can only be reached on tyler.lyson@gmail.com.

For images and a copy of the paper, kindly contact Erna van Wyk, Multimedia Communications Officer, University of the Witwatersrand on erna.vanwyk@wits.ac.za.

Erna van Wyk | EurekAlert!

More articles from Life Sciences:

nachricht Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University

nachricht How herpesviruses win the footrace against the immune system
26.05.2017 | Helmholtz-Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>