Acorn barnacle

Acorn barnacle 1.7 cm by Nantz McMillen




Kingdom: Animalia
Phylum: Arthropoda
Class: Maxillopoda
Order: Sessilia
Family: Balanidae
Genus: Balanus
Species: Glandula


Balanus glandula, otherwise known by their common name, acorn barnacles are crustaceans that typically live in the intertidal zone. While they are capable of living at depths of 1000m, they usually take up residency closer to shore. Barnacles have impermeable shells, which prevent water loss when the tide goes out.  In their adult form, they continuously grow calcified plates to their shell, which is protected by a cuticle that they occasionally molt. They are resilient creatures but do have predators, which include ochre stars, chitons, and moon snails.  They have a primitive naupliar eye that is photosensitive, allowing them to detect when predators are nearby. They spend their larval stage floating with plankton until they are mature enough to attach themselves permanently to a surface. They have cement glands at the base of their first antennae, which essentially allows them to cement themselves to a surface by means of their forehead. Barnacles use their cirri, feathery like appendages, to grab plankton which they pull back into the safety of their shell.  


Barnacles live in nearly every body of seawater on the planet.  They have adapted to hitch rides on ships and even baleen whales, forming a commensalistic relationship with them.  While colonies of barnacles attached to ships can create drag and must be removed for the sake of time and energy efficiency, it has been described as being less of a problem for whales.  This relationship benefits the barnacle as it travels through nutrient dense water filled with plankton, as it is the whale’s primary food source, and the whale is generally unaffected.

Banalus Glandula in their intertidal environment.  Featuring a hermit crab and sculpin for scale.

Banalus glandula in their intertidal environment. Featuring a hermit crab and sculpin for scale.




 Environmental Implications

Recent studies have indicated that barnacles are adapting to ocean acidification.  Because of their resilience and abundance around the world, they are a perfect candidate for documenting climate changes effect on ocean circulation. Their free floating larvae travels the ocean without settling on the ocean floor, allowing scientists to observe their migratory patterns.  Knowing barnacle migratory patterns will reveal the movement of the deep ocean currents that are potentially slowing down which would affect the ocean conveyor belt.  If these currents came to a halt, it would drastically affect the climate for the entire planet.

Barnacles in their environment.

Barnacles in their environment.




Rutsch, Poncie. “Barnacles Hold Clues About How Climate Change is Affecting the Deep Ocean” phys.or. 26 November 2014. Web.

Pansch, Christian at al. “Larval development of the barnacle Amphibalanus improvisus responds variably but robustly to near-future ocean acidification” Oxford Journals. 22. May. 2013. Web.

 Cowles, Dave “Balanus glandula Darwin, 1854” walla walla. 2005. Web.

Sajem, Yvette. “The Symbiotic Relationship Between a Barnacle Living On A Whale’s Skin.” Demand Media. Web.

Baillie, Katherine. “Deep Ocean Current May Slow Due to Climate Change, Penn Research Finds.” Penn News. 20 Mar. 2014. Web.

Copyright Nantz 2015