You may recognize Choriaster granulatus from such subreddits as r/mildlypenis, r/intentionallypenis, and r/oddlyarousing. The starfish is famous for its penis-like “arms” – but what you’re really looking at is a whole lot of head.
C. granulatus, commonly known as the granulated sea star, is found across the Indo-Pacific. It enjoys warm waters and chilling on everything from rocky, rubbly surfaces to coastal coral reefs. Granulated sea stars sometimes ride solo, but they can also be found in gangs.
They are carnivorous animals with mouths concealed beneath their doughy bodies, which have earned them the nickname "doughboy starfish" in honor of the Pillsbury Doughboy. It typically has the appearance of a classic five-armed sea star, but this can be deformed by parasitic limpets that are partial to clinging to their underside.
Its five “arms” are a great demonstration of the five-fold symmetry we see in starfish, which have no clear head or tail. If you were ever wondering where to stick a hat on one, you might gamble on the center, but in truth, these animals are basically all head.
The staggering discovery was made in a 2023 study that used a combination of imaging and genetic techniques to create a 3D atlas of starfish gene expression. This included micro-CT scanning, which illustrated the skeleton, muscles, and digestive, nervous, and water vascular systems of a starfish, combined with RNA tomography and in situ hybridization – staining genetic material with fluorescent labels – to show which genes were being expressed and where.
Their efforts revealed that the “head” of a starfish is, in fact, composed of headlike regions distributed in the center of its “body” and the center of each of its five limbs. Thus, what we think of as a starfish’s body is actually more like a head.
“It’s as if the sea star is completely missing a trunk, and is best described as just a head crawling along the seafloor,” said Laurent Formery, lead author of the new starfish study, in a statement. “It’s not at all what scientists have assumed about these animals.”
So before you go branding the granulated sea star a cluster of penises or the Pillsbury Doughboy, have a bit of respect and see it for the example of one of nature’s strangest heads that it truly is.
