2023-11-03 16:23:45
Zoology
A starfish is mostly heads
Researchers discovered that this strange animal did not have a torso or tail but several heads, in the center and in the middle of each branch.
PublishedNovember 3, 2023, 5:23 p.m.
The starfish is one of the few animals that does not have a bilateral body.
Getty Images
The starfish is a very strange animal. It is in fact one of the rare ones not to have a symmetrical body, like that of a human being for example. And scientists had a hard time knowing where the head or tail was in this echinoderm. Today, we know a little more thanks to researchers at Stanford and Berkeley universities.
In this study, published in «Nature», they started by capturing a three-dimensional snapshot of the shape and structure of the sea stars. Then they carried out genetic sequencing. All animals share similar genetic programming, according to a discovery awarded the Nobel Prize in Medicine in 1995. Which means that the genetic coding to make an arm or a leg is the same for everyone, the same for the other members.
“A simple head crawling along the seabed”
Genetic signatures associated with the development of a head were detected throughout the sea stars, notably concentrated in the center of the animal and in the middle of each arm. In contrast, gene expression from the torso and tail sections was largely absent, revealing that sea stars “present the most spectacular example of decoupling of the head and trunk regions that we know of today” , said French researcher Laurent Formery, the lead author of the study, cited by CNN. “It’s as if the starfish completely lacked a trunk and was best described as a simple head crawling along the sea floor.”
An image of the nervous system of a starfish.
Laurent Formery
The starfish is a little-studied animal, but learning more about creatures that are quite different from us can lead to answers that are just as interesting, or even more interesting, than discoveries about those that are similar to us.
Sea stars hatch from fertilized eggs and become larvae that float for weeks or even months before settling on the ocean floor. They transform a body which is then bilateral into pentaradial. This transformation remains a mystery, as is the fact that the starfish has a bilateral-bodied ancestor. New discoveries about the animal’s anatomy will advance research.
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