Balanus Glandula Class: Multicrustacea, Hexanauplia, Thecostraca, Cirripedia
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Phylum: Arthropoda, Crustacea Balanus glandula Class: Multicrustacea, Hexanauplia, Thecostraca, Cirripedia Order: Thoracica, Sessilia, Balanomorpha Acorn barnacle Family: Balanoidea, Balanidae, Balaninae Description (the plate overlapping plate edges) and radii Size: Up to 3 cm in diameter, but usually (the plate edge marked off from the parietes less than 1.5 cm (Ricketts and Calvin 1971; by a definite change in direction of growth Kozloff 1993). lines) (Fig. 3b) (Newman 2007). The plates Color: Shell usually white, often irregular themselves include the carina, the carinola- and color varies with state of erosion. Cirri teral plates and the compound rostrum (Fig. are black and white (see Plate 11, Kozloff 3). 1993). Opercular Valves: Valves consist of General Morphology: Members of the Cirri- two pairs of movable plates inside the wall, pedia, or barnacles, can be recognized by which close the aperture: the tergum and the their feathery thoracic limbs (called cirri) that scutum (Figs. 3a, 4, 5). are used for feeding. There are six pairs of Scuta: The scuta have pits on cirri in B. glandula (Fig. 1). Sessile barna- either side of a short adductor ridge (Fig. 5), cles are surrounded by a shell that is com- fine growth ridges, and a prominent articular posed of a flat basis attached to the sub- ridge. stratum, a wall formed by several articulated Terga: The terga are the upper, plates (six in Balanus species, Fig. 3) and smaller plate pair and each tergum has a movable opercular valves including terga short spur at its base (Fig. 4), deep crests for and scuta (Newman 2007) (Figs. 2, 4, 5). depressor muscles, a prominent articular Shell: ridge, and an articular furrow (Pilsbry 1916). Shape: Shell surrounding the barna- Aperture: The shell opening, from cle body is pyramidal in shape (see Fig. 99, which the cirri emerge when feeding, is con- Kozloff 1993) (Fig. 2). trolled by movement of the terga and scuta in Basis: Calcareous and flat, attached conjunction with adductor and depressor mus- to hard substrate, rendering B. glandula a cles. When closed, plates produce a distinct sessile, or attached barnacle and sinuous line at their junction in B. glandu- (Balanomorpha). la (Kozloff 1993). Wall: Formed by the six plates (Fig. Cirri: Feathery, black and white and conspic- 2) and composed of irregular, vertical, filled uous. Each of the six pairs of legs (=cirri), tubes, giving the exterior the appearance of bears 4–7 pairs of setae (Nishizaki and Car- rough ribbing. rington 2014). The cirri of B. glandula were Longitudinal Tubes: Only the first observed to exhibit ecophenotypic present in immature individuals (Newman plasticity, where individuals adjusted re- 2007). sponse time (i.e. cirral withdrawl) to specific Plates: Calcareous, nearly habitats. An adjustment from one habitat conical and columnar. Six in family Balani- (e.g. wave-exposed) to the next (e.g. protect- dae. Each plate is composed of parietes ed) occurred over a period of two molts (exposed triangular part) (Figs. 3a, 3b), alae (approximately 18 days) (Marchinko 2003). A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Hiebert, T.C. and M. Jarvis. 2015. Balanus glandula. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Spe- cies, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biology, Charleston, OR. Possible Misidentifications and by its unique and unusual membraneous There are three groups (i.e. superor- base. Semibalanus cariosus have terga with ders) of cirripeds including the Rhizocepha- a long pointed spur, quite different from la (parasites among crustaceans), the Acro- either B. crenatus or B. glandula. Semibala- thoracica (shell-less burrowing forms), and nus cariosus commonly co-occurs with B. the Thoracica. The Thoracica contains crenatus, B. glandula, as well as with 1,000 species worldwide including the mon- Chthamalus dalli. Juvenile S. cariosus will ophyletic taxa, Lepadomorpha, the stalked show a typical heavy ribbing and starry basis barnacles, and the Balanomorpha, or ses- outline, which would distinguish it from young sile barnacles (Perez-Losada et al. 2008; B. crenatus or B. glandula. Generally, these Chan et al. 2014). Among the sessile latter two species are found higher in the in- forms, there are four families represented tertidal than is S. cariosus, which occurs locally. The family Chthamaloidea includes mostly subtidally. members of the genus Chthamalus. Juve- Balanidae encompasses the genera nile Balanus glandula and Chthamalus dalli, Megabalanus, Paraconcavus, and Menesin- often found together, are very alike. The iella (each with one local species), Amphi- genus Chthamalus has alae on its rostral balanus (three local species) and Balanus plates, not radii (i.e. the rostral plate is (four local species). Balanus crenatus is overlapped, rather than underlapped, as in generally found in the intertidal at a lower B. glandula, by the rostrolateral plates). level than the ubiquitous and morphologically Chthamalus dalli is found both with and at similar B. glandula. Balanus glandula has no higher tide levels than B. glandula, and longitudinal wall tubes (except when young) individuals are usually brown. The family and it differs in the structure of terga and Tetraclitoidea has one species locally scuta: the terga are very wide and have (Tetraclita rubescens), and is characterized longer spurs and the scuta have no adductor by a wall that is composed of four plates ridges (compare Fig. 5 with B. glandula Figs. (rather than six in the Balanidae). 4, 5, this guide). Balanus crenatus, on the The remaining two families are the other hand, has a shell wall with a single row Balanidae and Archaeobalanidae. The Ar- of uniformly spaced tubes (Newman 2007). chaeobalanidae includes the genera Ar- Balanus crenatus is a difficult barnacle to matobalanus, Conopea, Hesperibalanus identify: "Not only does every external cha- and Semibalanus (each with one local spe- racter vary greatly in this species, but the in- cies). The latter genus includes a common ternal parts very often vary to a surprising local intertidal species S. cariosus (and for- degree, and to add to the difficulty, groups of mer member of the genus Balanus). An specimens do not rarely vary in the same isolated S. cariosus, is with splinter-like spi- manner” (Charles Darwin in Cornwall 1951). nes, nearly black cirri and is not likely to be Balanus nubilus, the giant acorn barnacle, is confused with another barnacle. It has a easily distinguished from B. glandula by its thatched appearance, being irregularly rib- large size, reaching 100 mm in diameter, and bed and its walls have uneven, longitudinal a shell aperture that is relatively large and tubes (Pilsbry 1916). However, where it is flaring (Newman 2007). Balanus trigonus is crowded or eroded, these spines may be a lower intertidal species with a southern worn off or not developed, and the barnacle distribution (to Monterey Bay, California). would have to be distinguished from other common barnacles by its terga and scuta, A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Ecological Information glandula individuals showed a negative Range: Type range includes Alaska to Baja correlation in abundance with substrate California (Darwin 1854), B. glandula was temperature in the mid-intertidal (Salish Sea, introduced to South America (Argentina) and Washington, Harley 2011). Japan (Kado 2003; Newman 2007; Rashidul Associates: Forms dense clusters with Alam et al. 2014). Chthamalus dalli, Nucella, mussles and Local Distribution: Ubiquitous in a wide limpets (including Lottia digitalis) at high tide variety of locations from the open rocky levels (Kozloff 1993; Newman 2007). shores to the salty or brackish bays of the Sometimes found on larger Balanus cariosus Oregon coast (Kozloff 1993), where popula- individuals. tions show genetic heterogeneity over great Abundance: One of the most abundant ani- distances (Barshis et al. 2011), except in mals on the coast with up to 70,000 individu- central California where gene flow is more als per square meter (Ricketts and Calvin restricted between populations (Sotka et al. 1971). Larval abundance can also be high in 2004). the plankton, where 10 cyprids per 200 liters Habitat: Very adaptable to a variety of habi- were reported in central California (Gaines et tats. Suitable substrates include rocks, pil- al. 1985). ings, wood, other crustaceans, molluscs, Life-History Information and barnacles. Often in conditions with Reproduction: Cirripeds usually brood their extreme exposure to sun, wind, rain and can eggs and B. glandula produces 2–6 broods/ tolerate estuarine conditions quite well, year, in winter and spring (Oct–May in south- including those of poor water circulation, low ern California), and through September on oxygen, and little wave action (Ricketts and Vancouver Island and December in Friday Calvin 1971). Populations in polluted areas Harbor (Høeg et al. 1987). Barnacles are one have been shown to exhibit lower genetic of the few sessile organisms with internal ferti- diversity, with more individuals of the same lization and plasticity in penis length has been haplotype (southern California, Ma et al. observed, with shorter penises in high wave- 2000). energy environments (Neufeld and Palmer Salinity: Collected at salinities of 30, but 2008). Individuals are hermaphroditic and can also survive at lower salinities (Ricketts self-fertilization is possible, but not common Balanus glandula and Calvin 1971). resists (MacGinitie and MacGinitie 1949; Yonge Balanus desiccation better than other spe- 1963). Spermcast spawning can occur cies (Newman and Abbott 1980). (Barazandeh et al.