Uncommon Descent Serving The Intelligent Design Community

Could the notochord have originated as muscle?

Share
Facebook
Twitter
LinkedIn
Flipboard
Print
Email
Marine worm Platynereis’ muscle resembles, in placement and genes, the notochord/spine /Kalliopi Monoyios

The marine worm Platynereis is considered a living fossil. Here, we prefer the term “durable species.”

From ScienceDaily:

Antonella Lauri and Thibaut Brunet, both in Arendt’s lab, identified the genetic signature of the notochord — the combination of genes that have to be turned on for a healthy notochord to form. When they found that the larva of the marine worm Platynereis has a group of cells with that same genetic signature, the scientists teamed up with Philipp Keller’s group at Janelia Farm to use state-of-the-art microscopy to follow those cells as the larva developed. They found that the cells form a muscle that runs along the animal’s midline, precisely where the notochord would be if the worm were a chordate. The researchers named this muscle the axochord, as it runs along the animal’s axis. A combination of experimental work and combing through the scientific literature revealed that most of the animal groups that sit between Platynereis and chordates on the evolutionary tree also have a similar, muscle-based structure in the same position.

The scientists reason that such a structure probably first emerged in an ancient ancestor, before all these different animal groups branched out on their separate evolutionary paths. Such a scenario would also explain why the lancelet amphioxus, a ‘primitive’ chordate, has a notochord with both cartilage and muscle. Rather than having acquired the muscle independently, amphioxus could be a living record of the transition from muscle-based midline to cartilaginous notochord.

The shift from muscle to cartilage could have come about because a stiffened central rod would make swimming more efficient, the scientists postulate.

But did the muscle conduct nerves from the brain throughout the body and back?

See also: Genetic program for a face long predates a recognizable face (Researchers: Our results show that coupling of Hox gene expression to segmentation of the hindbrain is an ancient trait with origin at the base of vertebrates.)

Follow UD News at Twitter!

Comments
It's just gotta be true because there's absolutely NO evidence to the contrary! ;-) -QQuerius
September 15, 2014
September
09
Sep
15
15
2014
07:03 PM
7
07
03
PM
PDT

Leave a Reply