Starfish arms are their heads, new study suggests

When you think of a starfish, you probably imagine a sea creature with five arms.

However experts at the University of Southampton now believe that isn't necessarily the case.

Their study has revealed that the entire body of a starfish is in fact its head!

Scientists think that they've evolved over time to shed their bodies to eventually become only heads!

Starfish, also known as sea stars, belong to a group of animals called echinoderms - which also includes sea urchins and sand dollars.

They have a unique shape which is arranged in five equal sections.

This is very different from their ancestors, which had a left and right-hand side which mirror one another - such as humans and many other animals.

Scientists have long been puzzled by the mystery of how these creatures evolved their distinctive star-shaped body.

However, a new international study by scientists involving the University of Southampton has helped shed light on this question.

They used 3D maps to look at starfish genes and compare them to other groups of animals such as vertebrates.

They found that genes associated with head development were found just about everywhere in young starfish, but genes that code for an animal's torso and tail sections were largely missing.

Experts say this suggests that starfish may have evolved their unique shape by losing other regions of their bodies and becoming just heads!

Dr Jeff Thompson from the University of Southampton explained: "When we compared the expression of genes in a starfish to other groups of animals, like vertebrates, it appeared that a crucial part of the body plan was missing.

"It seems the whole echinoderm body plan is roughly equivalent to the head in other groups of animals."

He added: "As someone who has studied them for the last ten years, these findings have radically changed how I think about this group of animals."