Poli's Stellate Barnacle

Chthamalus stellatus

Did you know that Barnacles, those weird bumpy things that attach themselves to rocks, are not only animals, but they are Crustaceans just like Crabs and Lobsters? Let's learn about one species today!

These Barnacles, named for Italian biologist Giuseppe Saverio Poli, can be found in Southern Europe and off the coasts of England and Ireland. They attach themselves to rocks and other firm objects in inter-tidal zones. Once attached, the Barnacles don't really go anywhere. They feed by reaching their tiny legs out from their shell and latching on to plankton and debris.

Poli's Stellate Barnacles have chalky-white shells that have kite-shaped openings as juveniles, and oval openings as adults. Underneath that shell, their tissue is bright blue with black and orange markings. The Barnacles are usually cone-shaped, but they become more tubular in crowded areas. They grow to a size of around 14mm, but the size is dependent on their habitat and food supply.

One thing I found particularly interesting is that all Poli's Stellate Barnacles are hermaphrodites. If isolated, the Barnacles can actually self reproduce, though in most cases they will take on a male or female role. "Male" Barnacles have very long sexual organs that they can use to search for "Females" in the nearby area. Keep in mind that this whole time the Barnacle itself remains latched on to a surface, and does not otherwise move. "Females" keep their fertilized eggs inside their shell with them until they hatch, and there can be up to 4,000 eggs at a time!

After hatching, the larvae are free-swimming and go through several molts until they hit their Cyprid stage. At this point in their life they are completely unable to feed, and must find a rock or something else to latch on to in order to metamorphose into their final shelled adult form. These Barnacles can live up to 5 years, and reach full maturity after around 10 months.

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IUCN Status : Not Listed
Location : Europe
Size : Diameter up to 14mm

Classification : Phylum : Arthropoda -- Subphylum : Crustacea -- Class : Maxillopoda
Order : Sessilia -- Family : Chthamalidae -- Genus : Chthamalus -- Species : C. stellatus