Evolution
The
radula is a structure unique to molluscs, a large phylum that
encompasses creatures from snails to giant squids. It is used in feeding
to scrape or cut food before it enters the esophagus. While almost all
molluscs have them, the features of a radula - such as arrangement of
teeth, or denticles - may vary greatly from one species to another due
to different diets. The image below shows the bea
k
and radula of the giant squid - note the backward pointing denticles to
cut and direct food. But how did the radula come to be?
To
answer this question, PhD candidate Martin Smith (University of Toronto)
examined 300 fossils of Odontogriphus and Wiwaxia using a
non-destructive type of Electron Microscopy. Odontogrihpus and Wiwaxia
are fossils from the Cambrian period, around 500 million years ago. The
mouthparts consisted of two to three rows of 17 similar teeth, a
symmetrical central tooth and smaller teeth on the edges - all moving
round a tongue scooping algae from the seabed. Factoring in how the
teeth would have moved and been replaced, Smith found he was looking at a
clear predecessor to the radula we see today.
"When I set
out, I just hoped to be a bit closer to knowing what these mysterious
fossils were," says Smith. "Now, with this picture of the earliest
radula, we are one step closer to understanding where the molluscs came
from and how they became so successful today."
Image credit: Sally Parker/Smithsonian Institution.
http://www.eurekalert.org/
The
radula is a structure unique to molluscs, a large phylum that
encompasses creatures from snails to giant squids. It is used in feeding
to scrape or cut food before it enters the esophagus. While almost all
molluscs have them, the features of a radula - such as arrangement of
teeth, or denticles - may vary greatly from one species to another due
to different diets. The image below shows the bea
k
and radula of the giant squid - note the backward pointing denticles to
cut and direct food. But how did the radula come to be?
To answer this question, PhD candidate Martin Smith (University of Toronto) examined 300 fossils of Odontogriphus and Wiwaxia using a non-destructive type of Electron Microscopy. Odontogrihpus and Wiwaxia are fossils from the Cambrian period, around 500 million years ago. The mouthparts consisted of two to three rows of 17 similar teeth, a symmetrical central tooth and smaller teeth on the edges - all moving round a tongue scooping algae from the seabed. Factoring in how the teeth would have moved and been replaced, Smith found he was looking at a clear predecessor to the radula we see today.
"When I set out, I just hoped to be a bit closer to knowing what these mysterious fossils were," says Smith. "Now, with this picture of the earliest radula, we are one step closer to understanding where the molluscs came from and how they became so successful today."
Image credit: Sally Parker/Smithsonian Institution.
http://www.eurekalert.org/
To answer this question, PhD candidate Martin Smith (University of Toronto) examined 300 fossils of Odontogriphus and Wiwaxia using a non-destructive type of Electron Microscopy. Odontogrihpus and Wiwaxia are fossils from the Cambrian period, around 500 million years ago. The mouthparts consisted of two to three rows of 17 similar teeth, a symmetrical central tooth and smaller teeth on the edges - all moving round a tongue scooping algae from the seabed. Factoring in how the teeth would have moved and been replaced, Smith found he was looking at a clear predecessor to the radula we see today.
"When I set out, I just hoped to be a bit closer to knowing what these mysterious fossils were," says Smith. "Now, with this picture of the earliest radula, we are one step closer to understanding where the molluscs came from and how they became so successful today."
Image credit: Sally Parker/Smithsonian Institution.
http://www.eurekalert.org/
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