Chthamalus / Balanus (Chthamalus.htm)

Chthamalus fissus Darwin, 1854

(Previously known as C. microtretus)/Balanus glandula Darwin, 1854

Small/Large acorn barnacle

General Description (from Morris et al. 1980 and Kendall et al. 2002):

C. fissus: small, up to 8 mm in diameter; brown-greyish; smooth with oval operculum; virtually indistinguishable from C. dalli in the field

B. glandula: bigger than C. fissus, up to 22 mm; with white diamond-shaped operculum; deeply ridged plates

Chthamalus fissus

Habitat and Range (from Morris et al. 1980):

C. fissus: common on rocks, pier pilings, and hard-shelled organisms, high and upper middle intertidal zones, San Francisco to Baja California

B. glandula: abundant on rocks, pier pilings, and hard-shelled animals, high and middle intertidal zones in bays and along outer coast; Aleutian Islands (Alaska) to Bahia de San Quintin (Baja California)

Chthamalus fissus

Balanus glandula with Chthamalus fissus

Biology:

Acorn barnacles are very common in the intertidal zone along the California coast. Chthamalus dalli and Balanus glandula are more common north of Point Conception, but all three species are found south of Point Conception (Raimondi et al. 1999). They spawn often and at variable times throughout the year (Hines 1978), which may explain the high densities occurring along the coast. Small acorn barnacles are more resistant to desiccation than large acorn barnacles and are found higher in the intertidal zone. Large acorn barnacles lower in tidal height are susceptible to predation by sea stars and predatory snails (Morris et al. 1980). Small acorn barnacles are believed to live around 3 years, whereas, large acorn barnacles are believed to live up to 10 years (Morris et al. 1980). Acorn barnacles are susceptible to high mortality from oil spills because oil can stick to high intertidal habitat (Raimondi et al. 1999). High acorn barnacle mortality has been reported in past oil spills (Foster et al. 1971; Chan 1973). Recovery times range from several months to several years (Vesco and Gillard 1980).

Balanus glandula with Chthamalus fissus

Can be confused with: Chthamalus dalli, which has strongly ridged or crested muscle scars on the inside of the scutal plates, unlike C. fissus, which has only a smooth-walled depression (Morris et al. 1980). C. dalli also has finely bipectinate setae on the ends of the second cirri, when viewed with a microscope, whereas C. fissus has coarsely bipectinate setae and a pair of basal pectintions enlarged as guards (Morris et al. 1980).

References:

Chan GL (1973) A study of the effects of the San Francisco oil spill on marine organisms. In Proceedings of joint conference on prevention and control of oil spills. American Petroleum Institute, Washington, D.C., pp 741-782

Foster MM, Neushul M, Zingmark R (1971) The Santa Barbara oil spill. Part 2. Initial effects on intertidal and kelp bed organisms. Environ Pollut 2:115-134

Hines AH (1978) Reproduction in three species of intertidal barnacles from central California. Biol Bull 154:262-281

Kendall A, Kusic K, Maloney E, Williams M (2002) List of species to be discussed at the 2002 MMS Taxonomic Workshop

Morris RH, Abbott DL, Haderlie EC (1980). Intertidal invertebrates of California. Stanford University Press, Stanford

Raimondi PT, Ambrose RF, Engle JM, Murray SN, Wilson M (1999) Monitoring of rocky intertidal resources along the central and southern California mainland. 3-Year Report for San Luis Obispo, Santa Barbara, and Orange Counties (Fall 1995-Spring 1998). OCS Study, MMS 99-0032, U.S. Bureau of Energy Management, Regulation, and Enforcement, Pacific OCS Region

Vesco LL and Gillard R (1980) Recovery of benthic marine populations along the Pacific Coast of the United States following man-made and natural disturbances including pertinent life history information. U.S. Department of the Interior, Bureau of Land Management Service, POCS Reference Paper No. 53-4