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Balanus glandula
Common name: Common acorn barnacle
Size:
Large specimens are about 1.5cm in diameter. The height is generally equal to diameter, however, colonizing B. glandula tend to grow nearly columnar.
Description:
White and/or grey and cone-shaped. A distinctive feature of B. glandula is the way the plates in the "crater" fit together when the animal is inactive (Kozloff, 2000).
Range:
Aleutian Islands, Alaska to southern California.
Habitat:
Generally found in Chthamalus fissus between low and high tide marks. B. glandula is commonly found on rocks in the high and mid-intertidal zones, and on various hard-shelled organisms in both exposed and sheltered locations. Also found on floats, pilings, rocks, and on the backs of crabs.
Life History:
B. glandula is often the most abundant barnacle in the upper portion of the intertidal zone, and is the most ubiquitous barnacle on the Pacific Coast. Barnacles are hermaphrodites which fertilize each other by means of a long penis. This barnacle reproduces between 2 and 6 times annually, with up to 30,000 young produced. Reproduction occurs mainly in the fall and winter when the climate is cooler. Adult size is reached within 2 years and live about 10 years, however some individuals have been known to live as long as 15 years.
Larva are called naplius, this is the first larval stage characterized by three pairs of appendages, (antennules, antennae and mandibles). After several molts larva enters cypris stage. This stage has all the appendages of naplius stage but additional mouth parts and six pairs of thoracic limbs and a bivalve shell. It is in cypris stage that C. glandula can attach to substrate by secreting a type of cement from the antennules.
Misidentification:
Chthamalus fissus, this is a stretch simple because the two are often found together. C. fissus is smaller, 8 mm in diameter, and has a smooth, oval operculum, whereas Balanus glandula is larger and has deeply ridged plates on the operculum.
Predators:
Nucella, Lottia, Pisaster, Pycnopodia, Leptasterias.
Links:
Balanus amphitrite of San Francisco Bay
Suggested Readings:
Kozloff E.N. 1973. Seashore Life of Puget Sound, the Straight of Georgia and the San Juan Archipelago. University of Washington Press.
Johnson M.J. and Snook H.J. 1955. Seashore Animals of the Pacific Coast. Dover Publications, Inc.
Last updated Friday, August 25, 2006, by Lisa Ferrier
