Grab & Go

NAME: Acorn

CLASSIFICATION: Genus and Species: ( glandula)

MAIN MESSAGES: Waves, tides, and currents shape Northern California’s rocky coast. A rich array of marine life endures and thrives here, well adapted to the challenging conditions. • Cold, nutrient-rich water wells up seasonally from the deep water along our coast and fertilizes surface waters; phytoplankton bloom in profusion, forming the base of food webs. • Climate change may bring changes to currents, water temperature, and salinity that could disrupt upwelling • The Gulf of the Farallones National Marine Sanctuary protects the area through research, education, and conservation. Barnacles depend on the quality of water for their health; they are used to monitor the health of the environment as heavy metal pollution is detectable in the growth of the shell.

DISTRIBUTION AND HABITAT: Found in the middle level of the tidal zone. This is the meeting place of the marine and the terrestrial environment, and the habitat of the is governed by the amount of time they are exposed to air, and the frequency with which such exposures occur. Thus, conditions are more terrestrial in the upper zone, and more marine in the lower zone. These animals are exposed to air for varying lengths of time, depending on the tidal flows. Notice the clustering of the individual animals. This “togetherness” provides better attachment against wave surge as well as efficient use of space in the competitive real estate market of the intertidal. Barnacles attach themselves to solid substrata, such as rock, pier pilings, whales, and the bottom of ships. Some species are also found on floating debris, attached to whales, sea turtles, corals, sponges, and sea snakes. .

DESCRIPTION AND DIET: The extends three to six pairs of feathery appendages from its shell plates that catch whatever small plankton the sea water brings- these could be small animals, organic fragments, and other suspended nutrients- and carry it to the mouth. Two pairs of plates on top open and close so that feeding appendages can be extended or protected. These appendages are pairs of modified legs that show the jointed, chitinous structure characteristic of . (Barnacles feed by attaching their heads to the substrate and kicking their legs through the water to catch food.) Thus, barnacles are often described as creatures that live on their heads and eat with their feet!

PREDATORS: Sea stars and predatory snails feed on barnacles. There is a type of whelk that can drill a hole in the barnacle’s shell. Grab & Go

REPRODUCTION: Barnacles have solved the problem of attached organisms getting together to reproduce very efficiently. They live in clusters close together. The adult barnacle uncoils its long penis and probes for a near by mate. (X-rated: use at your discretion! This has the longest penis in the world for its overall body size!) When a mate is found, it just transfers the sperm to its mate. Most barnacles are hermaphroditic, so any adult can serve as a mate to any barnacle of the same species. Fertilized eggs are brooded within the shell. The larvae, like all , molts and sheds its exoskeleton as it grows and develops. When it’s time to settle down, it looks for rough surfaces and adult barnacles of its own species. Then it attaches, using special cement in its antennae. It molts again, rotating its body so the appendages are facing upward. “Cement” glands serve to anchor the barnacle to the bottom of the substrate.

LIFE SPAN AND CONSERVATION: They may live 10 to 60 years. Barnacles are filter feeders and depend on the quality of the water for their health. Barnacles can be used to monitor the health of the environment. Because they incorporate minerals in their shells, heavy metal pollution is detectable in the growth of the shell and can tell biologists when the pollution occurred.

INTERESTING FACTS: Diverse species of barnacles can be found all over the world. Barnacles are animals. They are members of the marine branch of the phylum Arthopoda, (crustaceans), while the terrestrial branch includes insects such as flies, bees and ants! Because of their thick shells, barnacles are mistaken by many people for mollusks; however, the larval form and jointed legs clearly identify the animals as crustaceans. Most mollusks make their shells from carbonates in sea water, but barnacles are the only that makes a heavy external shell from carbon carbonates found in sea water. Empty shells provide refuge to small rock crabs and juvenile red octopuses

WHERE IN THE ACADEMY: California Coast- Decorator Crabs tank, Nudibranchs tank, (Balanus); Rocky Coast Main Tank and Discovery tidepool (when available), Acorn barnacle (Balanus glandula), Gooseneck barnacle (Pollicipes polymerus);

SOURCES: Science in Action: Bob Van Synoc, October 8, 2007; October 27, 2007

Docent Aquarium Cart Training Notebook, January 2005

Niesen, Thomas M.,The Marine Biology Coloring Book, Second Edition, HarperCollins Publishers, Inc., New York, NY, 2000.

The Steinhart Aquarium: A view for and by Docents and Guides, 2009

(April 2, 2010)