The mystery is an old one: Experts have long been trying to understand how creatures such as starfish, sea urchins and other animals with a fivefold body plan, called echinoderms, evolved from an ancestor with twofold symmetry, a body plan common in animals, including insects, molluscs and vertebrates.
“How the different body parts of echinoderms relate to those of other groups of animals has been a mystery to scientists for as long as we have studied them,” said study coauthor Jeff Thompson from the University of Southampton. in a statement. In their bilateral relatives the body is divided into head, trunk and tail. However, when looking at a starfish, it is impossible to tell how these sections relate to the bodies of bilateral animals.
In the new study led by Laurent Formery and Chris Lowe of Stanford University, scientists used a variety of hightech molecular and genomic techniques to understand where different genes were expressed during starfish development and growth. The researchers created a threedimensional map of the starfish’s genetics and discovered where certain genes were expressed during development, namely the genes that control the development of the ectoderm, which includes the nervous system and skin.