Long Presumed to Have No Heads at All, Sea Stars May Be Nothing But

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. But now, labs at Stanford University and UC Berkeley, each led by Chan Zuckerberg Biohub San Francisco Investigators, have published a study finding that the truth is closer to the absolute reverse. In short, while the team detected gene signatures associated with head development just about everywhere in juvenile sea stars, expression of genes that code for an animal’s torso and tail sections were largely missing.