A Volcano-Shaped Crustacean
Along the rocky shores of Chile and southern Peru lives a creature that looks like a mineral formation instead of an animal. The giant barnacle, Austromegabalanus psittacus, is a crustacean that builds a tall, cone-shaped fortress around itself. This shell, composed of twelve large calcite plates cemented together, can reach a height of 30 centimeters (12 inches). Locally known as "picoroco," this barnacle lives cemented to rocks in the intertidal and shallow subtidal zones, typically at depths between 2 and 20 meters.
Inside this protective casing, the barnacle is a filter-feeder. It uses its feathery thoracic limbs, called cirri, to comb the water for plankton. Picorocos often grow in dense clusters, sometimes forming hummocks with over 1,000 individuals per square meter. This gregarious behavior gives them an advantage when competing for space with other shoreline species. Their main predators, aside from humans, include the sea star Heliaster helianthus and the clingfish Sicyases sanguineus, though the fish can only prey on smaller barnacles.
An Anatomical Wonder
The reproductive biology of the picoroco is an adaptation to a sessile, or immobile, lifestyle. They are simultaneous hermaphrodites, each individual possesses both male and female reproductive organs. To mate, a barnacle extends a long penis to a neighboring individual to transfer sperm for internal fertilization. Barnacles in general have the largest penis-to-body-size ratio in the animal kingdom, with some species having an organ that can stretch up to eight times their body length. This reach is necessary for an animal that cannot move to find a partner.
After fertilization, the eggs are incubated inside the shell for three to four weeks. They hatch into free-swimming nauplius larvae, which drift as plankton for about 45 days, molting through six stages. The final larval stage, a 1-millimeter-long cyprid larva, seeks out a suitable hard surface, preferably near other adult barnacles, where it will attach itself for life. An individual can be sexually mature just six months after settling.
A Threatened Delicacy
The meat of the picoroco is a delicacy in Chilean cuisine, with a flavor often compared to crab or lobster. It is an ingredient in curanto, a traditional dish where various types of seafood and potatoes are cooked in a pit over hot stones. They are eaten steamed, in soups, or baked into savory pies called pasteles.
Harvesters, typically divers, use special tools to pry the valuable barnacles from the rocks. This intense fishing pressure has led to a significant decline in wild populations. Annual catch volumes have dropped, fluctuating between 200 and 700 metric tons in recent years. In response to overharvesting, efforts are being made to develop commercial aquaculture for the species, which could supply both local demand and potential export markets.