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Barnacles are sessile organisms that live in shells that are permanently attached to hard substrates. They are often thought to be closely related to mollusks because they live in shells. However because of scientific research, scientists found that barnacles are actually part of the crustacean class (The University of Puget Sound). They are closely related to crabs and lobsters. Their shells are made of calcite. They can live up to 10 years and can attach to many different substrates.

Barnacles are often found attached to crabs, boats, whales, and man made poles. Some barnacles are parasites but most barnacles are in commensal relationships. They use the host as help to get food. The host usually does not notice the barnacle is there. Once a barnacle attaches to its substrate, it never moves (A-Z Animals)The only part of a barnacle’s life where it moves is the larval stages.

barnaclefinalThe Napulis is the platonic larvae of a barnacle. Nauplius swims freely and molts many times before going into the next stage of becoming a mature barnacle (The University of Puget Sound). It is a segmented arthropod with one eye. They are little arthropods that are zooplankton. They are part of the Balanidae family that is the family of highly evolved sessile barnacles (A-Z Animals). Because they are zooplankton, they are found on the upper stratification of ocean. They usually float right below the surface. When they mature into adult barnacles they live in the upper mid stratification of water. Although they are sessile, they do live near the surface. The Naupilis larvae eat algae and diatoms.

Barnacles live in their shells for most of their lives, using their modified legs to eat plankton and detritus. The larvae stage eats smaller plankton as well as diatoms. Adult barnacles live in intertidal zones while the larvae tend to live at the surface of the water. Barnacles are adapted to live in areas where the tide goes down. They have evolved in order to conserve their water( University of Washington). Barnacles compete for space with muscles, however barnacles have adapted to live on top of muscles! Predators for barnacle larvae are zooplankton-eating animals. The top predator for barnacle adults is a whelk that is able to grind through the shell in order to reach the arthropod (A-Z Animals).

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Barnacles are filter feeders. Adult barnacles have appendages that reach out and collect food. The larvae and adult barnacle eat diatoms, smaller plankton, and detritus. When the young barnacle first attaches to a substrate, a thin layer of flesh wraps around the larva and creates an outer shell that can protect it from other predators. Barnacles have a lot of predators, especially when they are in the larval stage. The only species of barnacle that is edible is the goose barnacle. They are part of the diet of Western Europeans (University of Puget Sound).

Barnacles are hermaphrodites. They have male and female reproductive organs. The barnacle penis can extend to a nearby barnacle to fertilize its eggs. Barnacles are capable of fertilizing their own eggs however, that rarely occurs. The larval cycle lasts about 6 months. There are two stages of larvae. Once the eggs hatch they become a nauplis. This arthropod floats with other plankton and molts to become bigger. That is the longest part of the larval cycle. After the nauplis stage, the barnacle molts into a cypris. The cypris has a tougher exoskeleton and spends its time finding a place to live. Cyprii have been found to not eat at all during that phase. Their main objective is to find a permanent place to live (A Snail Odyssey).

Barnacles are one of the oldest marine species. Scientists believe that barnacles have been around for millions of years. Despite the growing pollution of the ocean, barnacles seem to have been little affected. This is because of the barnacle’s ability to close its shells to avoid polluted waters constantly (A-Z Animals).


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Based off the research I did on barnacles and based off my observations, barnacles are really interesting. We see them everyday on rocks and on piers when they are not in the water. I used to think that when barnacles were out of the water, they were dead and I never felt obligated to step around the organisms when walking on the Evergreen Beach. Barnacles may seem meaningless but I think that they can remind us of an important lesson. Although they seem lifeless they are in fact life. It is important to recognize that because humans easily dismiss other forms of life because we deem them worthless or not usable. We even do that amongst our own species. I find that it is very important to recognize all life as it is: it’s life. We are all part of the same cycle and all go through phases of life that brings us to where we are. All living things should be treated with the same respect and should be admired for their contribution to their ecosystem. It is easy to forget about plankton, diatoms, and barnacles until they are shown to you. I think it takes a truly conscious person to remember and acknowledge all animals, plants, microbes, and even us humans. We are all going through the same struggle of surviving on Earth. Humans should especially think about other life forms, considering we are making it harder for them to survive.

Barnacle Larvae Life Cycle Animation by Breanna Swayze

“Acorn Barnacle  ·  University of Puget Sound.” Acorn

Barnacle  ·  University of Puget Sound. Slater Museum of

Natural History, n.d. Web. 15 Nov. 2015.



COPULATION & LARVAL DEVELOPMENT. N.p., n.d. Web. 19 Nov. 2015.

“Barnacle.” (Cirripedia). A-Z Animals, n.d. Web. 19 Nov. 2015.

Marine Ecology Class. “Barnacles.” Barnacles. University of

Washington, Tacoma, 2007. Web. 15 Nov. 2015.

Copyright 2015 Breanna-Brummett-Swayze