Balanus glandula is an acorn barnacle, occurring in the high-mid intertidal of much of the rocky coastline of western North America, where it can be one of the most abundant solitary animals, reaching densities of more than 70,000 individuals per square meter (Morris et al., 1980; Ricketts et al., 1985).

Biology/Natural History: Often the most abundant barnacle in the upper half of the intertidal zone (can reach densities of up to 70,000 per square meter), and the most nearly ubiquitous barnacle species on the Pacific coast. It can obtain oxygen both from the air and underwater. Barnacles are hermaphrodites which fertilize one another internally by means of a long penis. The eggs are brooded by the parent, and released as nauplius larvae. Up to 6 broods of 1000-30,000 young may be produced per year from this species. After 5 molts the larva becomes a nonfeeding cypris with 6 pairs of legs. The cypris attaches itself to a substrate by an antennal gland and metamorphoses into the adult form. Cyprids avoid rocks which Nucella lamellosa, an important predator, has recently crawled across, and also rocks with the red alga Petrocelis middendorffii. Adult size is reached in 2 years and lifespan is about 10 years, Barnacle molts are frequently seen debris in marine habitats. Predators include oysterdrill snails such as Nucella lamellosa, the ribbed limpet Lottia digitalis (bulldozes and feeds on juveniles; barnacles 6.7 mm diameter have a refuge in size), seastars such as Pisaster ochraceous, Pycnopodia helianthoides, Evasterias troschelii, and Leptasterias hexactis, goldeneye ducks, gulls, and even the nemertean worm Emplectonema gracile and the barnacle nudibranch Onchidoris bilamellata. Juvenile rockfish feed on the larvae swimming through kelp beds. Competitors include Semibalanus cariosus and the mussels Mytilus trossulus and M. californiensis, to the shells of which it often attaches. In many areas of the upper intertidal juveniles of this species compete with Chthamalus dalli juveniles by pushing them off the rock. Chthamalus is usually common only in the zone above where Balanus glandula thrives. Less common in estuaries. While it has no eyes, this species is sensitive to light and will rapidly withdraw if a shadow passes over it.

Balanus glandula has recently become established in Japan and in Argentina. In Japan it is directly competing with B. albicostatus.

A sessile (acorn) barnacle in which the rostrum overlaps the rostrolateral wall plates on either side of it, the tips of the terga are not drawn out into a beak, the lines of contact between the terga and scuta are sinuous, and the interior of the base of the shell has numerous centripetal ridges. The scuta have a diagonal line of pits. The inner surface of the scuta and terga is black, and especially in small individuals this shows through to the outside as a dark patch in the center of the scutum where the inner surface is excavated into a deep pit and the scutum is thin. The six wall plates are solid, not filled with hollow longitudinal tubes (except in some young individuals), and do not have fingerlike projecting spines pointing downward. The base is calcified and leaves a calcium deposit on the rock when removed (photo) An extremely common intertidal species, especially in the upper half. Diameter to 2.2 cm, but usually 1.5 cm or smaller. The height is usually about equal to the diameter, unless the barnacles are so crowded that they grow very tall and thin (photo). Walls usually white or grayish white, may have longitudinal ribs (which are often eroded away except in small individuals).

Argentina, Atlantic, Canada, Pacific Ocean, South Africa, USA

Aleutian Islands south to Bahía de San Quintín in Baja California (Morris et al., 1980).

B. glandula has recently established in Japan and Argentine, likely introduced via shipping ballast water (larvae) or hull-fouling (adults). In Japan it competes with B. albicostatus (Kado, 2003).

Geographical Range: Aleutian Islands, Alaska to Bahia de San Quintin, Baja California; recently introduced at Puerto de Mar del Plata, Argentina.

Shell to 22mm diameter (Morris et al., 1980)

“The sinuous line of contact between the terga and scuta distinguish this species from most other intertidal barnacles. Semibalanus balanoides has a sinuous line of contact but also has no centripetal ridges at the interior base of the shell. Chthamalus dalli has a straight, crosslike junction between the terga and scuta and the rostrum is overlapped by the rostrolaterals.” (Cowles et al., 2002)

Balanus glandula is similar in size and general shell morphology to Balanus crenatus (Morris et al., 1980).

How to Distinguish from Similar Species: The sinuous line of contact between the terga and scuta distinguish this species from most other intertidal barnacles. Semibalanus balanoides has a sinuous line of contact but also has no centripetal ridges at the interior base of the shell. Chthamalus dalli has a straight, crosslike junction between the terga and scuta and the rostrum is overlapped by the rostrolaterals.

Known from rocky shores.

B. glandula occurs in the high and mid-intertidal, attached to rock or other hard surfaces -- artificial (pilings, floats) or biological (other organisms). They’re common in the exposed outer coast, as well as in bays and estuaries. (Morris et al., 1980)

Depth range based on 130 specimens in 1 taxon.
Water temperature and chemistry ranges based on 103 samples.

Environmental ranges
  Depth range (m): -2 - 45.5
  Temperature range (°C): 10.119 - 10.345
  Nitrate (umol/L): 5.774 - 6.931
  Salinity (PPS): 31.692 - 32.028
  Oxygen (ml/l): 6.535 - 6.616
  Phosphate (umol/l): 0.883 - 0.974
  Silicate (umol/l): 12.975 - 16.001

Graphical representation

Depth range (m): -2 - 45.5

Temperature range (°C): 10.119 - 10.345

Nitrate (umol/L): 5.774 - 6.931

Salinity (PPS): 31.692 - 32.028

Oxygen (ml/l): 6.535 - 6.616

Phosphate (umol/l): 0.883 - 0.974

Silicate (umol/l): 12.975 - 16.001
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Depth Range: Intertidal, mostly in the upper half

Habitat: Mainly on intertidal rocks. Open ocean and protected waters. Also common on pilings and on floats.

Filters food (plankton and edible detritus) from the water during high tide, using it’s cirri (6 pairs of thoracic appendages).

Balanus glandula preys on:
plankton
detritus
phytoplankton
zooplankton

Based on studies in:
USA: California, Monterey Bay (Littoral, Rocky shore)

This list may not be complete but is based on published studies.

Balanus glandula is prey of:
Syllis spenceri
Thais emarginata
Acanthina spirata
Emplectonema gracilis
Arenaria melanocephala

Based on studies in:
USA: California, Monterey Bay (Littoral, Rocky shore)

This list may not be complete but is based on published studies.

On juveniles & adults: include Nucella lamellosa (snail); Lottia digitalis (limpet); Pisaster ochraceus, Pycnopodia helianthoides, Evasterias troschelli, Leptasterias hexactis (sea stars); Emplectonema gracile (nemertian worm); Onchidoris bilamellata (nudibranch), gulls, goldeneye ducks.

On larvae: include juvenile rockfish

(Cowles et al., 2002)

Mothers brood eggs, which are released into the water as nauplius larvae. These planktonic larvae undergo five molts to become a non-feeding cypris with six pairs of legs. Cyprids attach to suitable substrate (avoiding potential predators or competitors) and metamorphose into the adult form. They reach adult size in about two years. The entire lifespan is about 10 years. (Cowles et al., 2002)

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 912
Species: 924
Species With Barcodes: 1