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3D realization of the starfish gene expression process
Structures similar to the heads of other animals discovered
Animation SpongeBob main characters SpongeBob and Starfish Daddy (right). Screenshot of Nickelodeon Korea YouTube channel
Starfish are mysterious animals. This is because even if part of the body is cut off, it grows back, and its unique star-shaped body cannot be found in other animals. The evolution of starfish has been a mystery that has puzzled scientists for a long time. However, recent research results have come out that could completely change the common sense we have had about starfish. On the 1st (local time), researchers at the University of Southampton in the UK said, “As a result of examining the gene expression process of starfish using cutting-edge molecular and genome analysis technology, we found that the body part we had previously considered the ‘body’ of echinoderms such as starfish is actually the ‘head.’ “It’s close to,” he said. This study was published in the international academic journal ‘Nature’.
A study has shown that the body of a starfish is actually closer to the head. Provided by University of Southampton
Echinoderms are a group of animals that live in the sea and include starfish, sea urchins, sea cucumbers, etc. and have a radial body shape. Echinoderms have a ‘5-radial symmetry’ body structure in which body parts are arranged into five equal parts. This can be said to be a very different structure from humans and many other animals that exhibit left-right symmetry.
Deuterostomes are organisms in which the first tube formed during embryonic development from a fertilized egg becomes the anus, and later the mouth is formed. On the other hand, organisms that develop mouths first are called progenitors. Deuterostomes are divided into chordates (b left), hemicordates (b middle), and echinoderms (b right), and starfish are the representative echinoderms. Humans are included in the chordates. c are four hypotheses that address how echinoderms developed. Provided by University of Southampton
Dr Geoff Thompson, co-author of the study from the University of Southampton, said: “It was unclear how the unusual body structure of echinoderms was related to the general structure of other animals. “While the bodies of bilaterally symmetrical animals are divided into the head, torso, and tail, it is impossible to tell how each part of a starfish’s body is made up just by observing it.” University press releasesaid in Therefore, we collaborated with a research team led by Stanford University biologist Professor Chris Low to compare molecular markers of starfish and other deuterostomes. Deuterostomes are a broader classification of animals that includes echinoderms, and also includes vertebrates such as humans, which have symmetrical structures. Humans and starfish may feel very distant phylogenetically, but they are the same deuterostome, so they can be said to be closer than the progenitors of octopus, squid, and insects. Since echinoderms and vertebrates share a common ancestor, the researchers compared their developmental processes to understand how echinoderms evolved their unique body structures. First, we looked at how genes are expressed during the development and growth of starfish using cutting-edge molecular and genome analysis technologies. The shape and structure of the animal were also investigated in detail through micro city (CT) scanning. Then, they created a three-dimensional structure of the gene structure through RNA tomography and recorded which genes were expressed and how they were expressed during development.
The body structure of a starfish discovered through RNA tomography (a). Gray represents the skeleton, yellow represents the digestive tract (mouth), purple represents the water system, and blue represents the central nervous system. Area division to determine the body structure of starfish (b). Provided by University of Southampton
This was compared with echinoderms, which are very closely related, but have a bilaterally symmetrical structure, and with vertebrates. As a result, acorns and vertebrates showed clear differences in the genetic structure of the head and body, but in the starfish genes, only gene structures that were activated in the heads of symmetrical animals were found. Dr Geoff Thompson said: “It appears that starfish do not have a body. When comparing the starfish’s genes with those of other animals with symmetrical structures, genes normally involved in forming the body were not expressed in the starfish’s outer shell. “In the body structure of echinoderms, the body can be said to correspond to the head of other animals,” he explained. Starfish also begin their lives as larvae with both sides symmetrical until they become full adults. Researchers said the ‘five arms’ extending from the center of the adult starfish are extensions of the head rather than body areas like the tentacles of an octopus. To summarize the anatomical structure of a starfish, it can be said that the head has five protrusions, the mouth faces the ground, and the anus faces upward. They added that because the body genes were lost at some point during the evolution of echinoderms, they are currently studying whether there are any animals with intermediate stages in the fossil record.
Starfish have many tube feet attached to five structures extending from the center of the body. They use their tube feet to move and grab food. Getty Image Bank
Dr. Thurston Rakali of the University of Victoria, Canada, who was not involved in the study, said this study shows how five-radial symmetry body shapes like starfish evolved. “Simply put, starfish walk on the sea floor with their lips. “It can be thought that the original function of bringing food to the mouth has been modified to perform walking with the edges of the lips,” he told the British Guardian. Starfish have a mouth below the center of the body (belly) and an anus above (back). The abdomen has many tube feet hanging like tassels along each radial structure. Although they do not have a heart or brain, they have not evolved a circulatory system, but they breathe, excrete, move, and collect food through a unique water system (an organ that transports and uses water in the body). Cited paper: Nature, DOI:doi.org/10.1038/s41586-023-06669-2
Reporter Kim Ji-sook suoop@hani.co.kr