Phylum: Arthropoda, Crustacea Balanus nubilus Class: Theocostraca, Cirripedia Order: Thoracica, Sessilia The giant barnacle Family: Balanidae Description Size: Largest barnacle on the Pacific coast, plate edge marked off from the parietes by a and probably in the world (Ricketts and Calvin definite change in direction of growth lines) 1971), with individuals up to 100 mm in (Newman 2007). The plates themselves diameter, and nearly as tall (Cornwall 1951). include the rostrum, opposite it the carina and The illustrated specimen (from Coos Bay) is between the carina and rostrum are the four 90 mm in diameter. side plates, the carinolateral and rostrolateral Color: Shell dirty white with interior of scuta plates (see Fig. 3, Balanus glandula, this and terga (see Plate 18, Kozloff 1993) buff guide). Internal surfaces with fine horizontal and tergal beak usually purple tipped ribbing above and smooth near base, (Cornwall 1951). particularly in older specimens (Pilsbry 1916). General Morphology: Members of the Radii rather narrow (Darwin 1854). Cirripedia, or barnacles, can be recognized by Opercular Valves: Thick and their feathery thoracic limbs (called cirri) that yellowish, buff on interior but never white. are used for feeding. There are six pairs of Tergal beaks project above orifice edge cirri in B. nubilus. Sessile barnacles are (Cornwall 1977). Tergal and scutal adductor surrounded by a shell that is composed of a and depressor muscles are very thick in B. flat basis attached to the substratum, a wall nubilus (2 mm and 1.4 mm, respectively, formed by several articulated plates (six in Hoyle and Smyth 1963). Balanus species) and movable opercular Scuta: External surface with valves including terga and scuta (Newman prominent growth lines, a deep canal from 2007) (Figs. 1, 3, 4). apex and downward in old eroded specimens Shell: Exterior can be rugged and worn with (Fig. 4b). Internally with low articular ridge well-developed ribs that become eroded with that has a very narrow articular furrow. The age (Figs. 1, 2) (Cornwall 1977). prominent adductor ridge is large and with a Shape: Steeply conical and, like other shallow adductor pit. barnacles, they can become cylindrical when Terga: Beak triangular and crowded. Young specimens can also be often purple (Fig 4a), especially in older cylindrical (Henry 1940). specimens (Cornwall 1951). External growth Basis: Calcareous and flat, attached ridges narrow and regular, with narrow, to hard substrate, rendering B. nubilus a shallow longitudinal furrow. Internally, sessile, or attached barnacle numerous depressor muscle crests. Tergal (Balanomorpha). Barnacle base is thick, spur is wide at base and tapers to a narrow porous at edges and thin at center. truncate end (Fig. 4a). Moderate articular Wall: ridge is with shallow broad articular furrow Longitudinal Tubes: A single (Fig. 4a). row of tubes is uniform and within shell walls Aperture: Large, flared and with a (Ricketts and Calvin 1971). jagged edge (Cornwall 1977). Plates: Calcareous, nearly Cirri: Six pairs of conspicuous feathery conical and columnar. Six in family feeding appendages. Balanidae. Each plate is composed of parietes (exposed triangular part), alae (the plate overlapping plate edges) and radii (the Hiebert, T.C. 2015. Balanus nubilus. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Species, 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. A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12695 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Possible Misidentifications Balanidae encompasses the genera There are three groups (i.e. superorders) of Megabalanus, Paraconcavus, and cirripeds including the Rhizocephala, Menesiniella (each with one local species), (parasites among crustaceans), the Amphibalanus (three local species) and Acrothoracica (shell-less burrowing forms) Balanus (four local species). Balanus and the Thoracica. The Thoracica contains nubilus, is easily distinguished from other 1,000 species worldwide including the species by its large size and a shell monophyletic taxa, Lepadomorpha, the aperture that is relatively large and flaring stalked barnacles, and the Balanomorpha, (Newman 2007). Balanus trigonus is a or sessile barnacles (Perez-Losada et al. lower intertidal species with a southern 2008; Chan et al. 2014). Among the sessile distribution (to Monterey Bay, California). forms, there are four families represented Balanus crenatus is generally found in the locally. The family Chthamaloidea includes intertidal at a lower level than the ubiquitous members of the genus Chthamalus, which and morphologically similar B. glandula. has alae on its rostral plates, not radii. Balanus glandula has no longitudinal wall Chthamalus dalli is found both with and at tubes (except when young) and it differs in higher tide levels than is B. glandula, and the structure of terga and scuta: the tergum individuals are usually brown. The family is very wide and has longer spurs and the Tetraclitoidea has one species locally scutum has no adductor ridge. Balanus (Tetraclita rubescens) and is characterized crenatus, on the other hand, has a shell wall by a wall that is composed of four plates with a single row of uniformly spaced tubes (rather than six in the Balanidae). (Newman 2007). The remaining two families include the Balanidae and Archaeobalanidae. The Ecological Information Archaeobalanidae includes the genera Range: Type region is Monterey Bay, Armatobalanus, Conopea, Hesperibalanus California (Cornwall 1951). Known and Semibalanus (each with one local distribution includes the west coast of North species). The latter genus includes a America from the southern boundary of common local intertidal species S. cariosus Alaska to the mid Baja California coast. (and former member of the genus Balanus). Local Distribution: Common in Coos Bay An isolated S. cariosus, is with splinter-like and at several locations along the South spines, nearly black cirri and is not likely to Slough as well as south in Port Orford (Pilsbry be confused with another barnacle. It has a 1916). thatched appearance, being irregularly Habitat: Suitable substrates include pilings in ribbed: its walls have uneven, longitudinal bays with strong tidal action (Cornwall 1951), tubes (Pilsbry 1916). However, where it is rocks, shell hash and kelp holdfasts (Cornwall crowded or eroded, these spines may be 1977). Largest specimens are observed on worn off or not developed, and the barnacle fairly exposed wharf pilings where individuals would have to be distinguished from other can grow on top of each other to make common barnacles by its tergum and accretions one foot high (Ricketts and Calvin scutum, and by its unique and unusual 1971). membraneous base. Balanus nubilus, would Salinity: Collected at salinities of 30 and no be most likely to be confused with S. known collections from brackish water. cariosus at subtidal levels. Both species, as Balanus nubilus individuals can regulate pH juveniles, have strong ribs. S. cariosus has within their muscle fibers, but require external the characteristic starry border, however, sodium ions to do so (Boron et al. 1981). that B. nubilus lacks. Both species have a Considerable research is focused on the tergal plate with a long spur (Figs. 3b, 4a), physiology and neuroscience of B. nubilus but that of S. cariosus is pointed, while it is (e.g. Hoyle and Smyth 1963; Morris and truncate in B. nubilus. The cirri of S. Lecar 1981; Stockbridge and Ross 1984; cariosus are conspicuous and almost black. Ross et al. 1986; Callaway et al. 1989). Hiebert, T.C. 2015. Balanus nubilus. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Species, 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. Temperature: From temperate waters. antennae, secretes a cement and builds the Tidal Level: From low to shallow waters (3–6 adult calcareous shell (Ricketts and Calvin meters) and occasionally to 55 meters 1971). Cyprids are oblong and composed of (Cornwall 1977). a bivalve shell, six thoracic appendages, a Associates: Often encrusted with other pair of compound eyes and a conspicuous barnacles, sea stars and anemones on lipid reserve anteriorly (Fig. 3, Arnsberg 2001; overhanging rocks (British Columbia, Canada, Figs. 22.2–22.3, Chan et al. 2014). Cyprids Cornwall 1951). Boring sponges can erode prefer rough surface for settlement (Yonge shells (Cornwall 1977). Individuals also occur 1963). Cyprid larvae in B. nubilus are on boat bottoms with mussels and congeners characterized by a broadly rounded anterior (MacGinitie and MacGinitie 1949) and is often and narrow posterior and a large size (800– covered with brown furry mats of the 1000 µm) (Fig. 12, Arnsberg 2001). The entoproct, Barentsia (Pilsbry 1916). cyprids of B. crenatus are most similar to Abundance: The second most common those of B. nubilus, but they have a narrower barnacle of the low intertidal zone (most anterior, a distinct evenly curved abundant is Semibalanus cariosus, Pilsbry posterodorsal margin, and black pigment 1916). More common in Puget Sound, carapace spots (Arnsberg 2001). Washington and north (Ricketts and Calvin Juvenile: Often with cylindrical morphology. 1971) where individuals