For centuries, naturalists have puzzled over what might constitute the head of a sea star, commonly called a "starfish." When looking at a worm, or a fish, it's clear which end is the head and which is the tail. But with their five identical arms—any of which can take the lead in propelling sea stars across the seabed—it's been anybody's guess how to determine the front end of the organism from the back. This unusual body plan has led many to conclude that sea stars perhaps don't have a head at all.

Researchers at Stanford University and UC Berkeley, led by Chan Zuckerberg Biohub San Francisco Investigators, found that gene signatures associated with head development were found in juvenile sea stars, but expression of genes that code for an animal's torso and tail sections were largely missing. The researchers used high-tech molecular and genomic techniques to understand where different genes were expressed during the development and growth of sea stars. They also found that molecular signatures typically associated with the front-most portion of the head were localized to the middle of each of the sea star's arms, with these signatures becoming progressively more posterior moving out towards the arms' edges. The research suggests that over evolutionary time, sea stars lost their bodies to become only heads.

Starfish are basically heads crawling around using their lips. Uhhhhhh