February 19, 2024

Reggie Dao

11th Grade

Fountain Valley High School

As you stroll along the beach and kick sand into the shore, there is always a creature in the corner of your eye that stands out among the scattered seashells and seaweed. That prickly-skinned, sharp-edged animal glistens on the protruding rock, un-moving, and intrigues your curiosity to find out why its shape is the way it is. This familiar, unusual sea creature is known as a starfish, its name coined from their body holding a close resemblance to a star shape. The question of how their body shape formed has always been lingering in the air, and the history of their genetics can explain why their body is different from their sea neighbors.

How exactly did their body shape develop? Is it even a body, or could it be a different body part for a starfish? A shocking surprise was made by scientists as it was believed by most that the shape of its body functioned like a body, but it was more of a head according to studies at the University of Southampton. This also applies to other unique sea creatures, such as sand dollars and sea urchins, and they all are classified as “echinoderms.” A fivefold symmetric body is what they all share with their bodies being cut into five equal sections, contrasting from the usual right and left sides that most animals and humans have. On a mission to discover the mystery of the starfish body, scientists at UC Berkeley, Pacific BioSciences, and Stanford utilized RNA tomography to dive deeper into the starfish model. As they compared the genes to other animals, they realized there was a set of genes that weren’t present, which was the trunk. This discovery shows that starfish lost their trunk region to morph into their final stage of a fivefold body, which is also the same for sea urchins and sand dollars. Without the trunk region expressed in a starfish, it acts more like a head according to these top universities. They contain only gene expressions incorporated with head development, with genes that remove their head and tail completely.  

Although the mystery of its body shape is no longer a mystery, there is still more research and gaps to study about these creatures to fully understand their history, as they keep evolving over the years. It is strange to find out that a starfish functions as a huge walking head, rather than a body with the usual head and tail.