This subtidal barnacle has
6 plates and the rostrum overlaps the adjacent plates. Its
are drawn out into a beak (photo). The outside of the plates
fairly smooth or with shallow longitudinal striations, not much
The base is well calcified. The tubes within the wall plates
have transverse septa. The overlapping portions of the plates
usually glossy (photo). Usually less than 3 cm diameter but
up to 5 cm. In my experience this barnacle is usually as tall
taller than wide.
Balanus rostratus Hoek, 1883
|Balanus rostratus from about 100 m
depth, San Juan Channel,
|(Photo by: Dave Cowles,
How to Distinguish from
Balanus balanus has septae in the tubes of the wall
grows much larger,
usually has heavily eroded plates, has longer beaks, and appears bright
orange-yellow when it opens. Semibalanus cariosus
projections on the outside of the plates. Balanus
crenatus looks superficially similar but has no
(At least along
our Pacific Coast and off Japan)
(In my experience this
barnacle is found mainly quite deep)--below normal SCUBA depths.
composition indicates that small individuals eat mainly detritus while
larger individuals feed mainly on diatoms.
Kozloff 1987, 1996
Muramoto, Dong-Hao Jin, Yoko Niino, Kazue Fujiwara, Shizuya Kabuto,
Ogawa, Michitoshi Toda, and Hisao Kamiya, 2001.
the amino acid sequences of acorn barnacle lectins showing different
activities toward the crystal growth of calcium carbonate.
Science 67:4 pp. 703-
FV, Chailakhian LM, Vereninov AA, 1972. Relative
of the membrane of giant muscle fibers of Balanus balanus
Balanus rostratus (Hoek) for potassium, sodium and
Biofizika 17:1 pp. 63-69 (in Russian)
Zhukova, Natalia V., 2000. FATTY ACID COMPONENTS OF
OF BARNACLES, HESPERIBALANUS HESPERIUS AND BALANUS
(CIRRIPEDIA), AS INDICATORS OF FOOD SOURCES. Crustaceana 73:5
General Notes and
Observations: Locations, abundances,
The joints where the plates overlap are shiny.
This is the scutum (left) and tergum (right) from an individual eaten
by a seastar. The tergum is beaked, as can be seen at top.
This is the view of the inside of the tergum (left) and scutum (right).
The wall plates are formed of hollow tubes, the openings of which are
visible at the bottom of this photo.
Longitudinal striations can be seen on the inside of the wall plates,
as seen here.
The base of the plates is at the bottom.
Three Balanus rostratus
barnacles have hitched a ride on this Chlamys hastata
scallop. The rest of the surface of the scallop is covered with the
sponge Myxilla incrustans.
Photo by Dave Cowles, July 2017
Authors and Editors of Page:
Dave Cowles (2006): Created original page