Siliqua Patula Order: Imparidentia, Adapedonta the Flat Razor Clam Family: Solenoidea, Pharidae, Siliquinae

Home , Adapedonta, Euheterodonta, Pharidae, Siliqua (bivalve), Solenidae, Tagelus

Class: Bivalvia, Heterodonta, Euheterodonta Siliqua patula Order: Imparidentia, Adapedonta The flat razor clam Family: Solenoidea, Pharidae, Siliquinae

Taxonomy: The familial designation of this surround a mantle, head, foot and viscera species has changed frequently over time. (see Plate 393B, Coan and Valentich-Scott Previously in the Solenidae, current intertidal 2007). Solenid and pharid bivalves are bur- guides include S. patula in the Pharidae rowers and some species are quite fast (e.g., (e.g., Coan and Valentich-Scott 2007). The Siliqua patula, see description in this guide). superfamily Solenacea includes infaunal soft They have shells that are longer than wide bottom dwelling bivalves and contains the and often razor-like at the opening edge (see two families: Solenidae and Pharidae (= Plate 397G, Coan and Valentich-Scott 2007). Cultellidae, von Cosel 1993) (Remacha- Body: (see Plate 29 Ricketts and Calvin Trivino and Anadon 2006). In 1788, Dixon 1952; Fig 259 Kozloff 1993). described S. patula from specimens collect- Color: ed in Alaska (see Range) and Conrad de- Interior: (see Fig 5, Pohlo 1963). scribed the same species, under the name Exterior: Solen nuttallii from specimens collected in Byssus: the Columbia River in 1838 (Weymouth et Gills: al. 1926). These names were later synony- Shell: The shell in S. patula is thin and with mized, thus known synonyms for Siliqua pat- sharp (i.e., razor-like) edges and a thin profile ula include Solen nuttallii, Solecurtus nut- (Fig. 4). Thin, long, fragile shell (Ricketts and tallii. Occasionally, researchers also indi- Calvin 1952), with gapes at both ends cate a subspecific epithet (e.g., Siliqua sili- (Haderlie and Abbott 1980). Shell smooth in- qua patula) or variations (e.g., Siliqua patula side and out (Dixon 1789), elongate, rather var. nuttallii, based on rib morphology, see cylindrical and the length is about 2.5 times Possible Misidentifications) (Oldroyd the width. 1924). Interior: Prominent internal vertical rib extending from beak to margin (Haderlie and Description Abbott 1980). Size: Individuals up to 190 mm (Haderlie Exterior: Both valves are similar and and Abbott 1980; Coan and Valentich-Scott gape at both ends. The beaks are subcentral 2007), with average size adults over 40 mm and toward anterior end, and the posterior (Coan and Carlton 1975). end is round. Color: Periostracum is smooth, brown, Hinge: The hinge ligament is com- shiny, and lacquer-like (Ricketts and Calvin pletely external, and not seated on a nymph 1952). The shell exterior is white, obscurely (Fig. 2). The left valve is with four cardinal rayed, with faint violet coloration and the in- teeth, while the right valve is with two (Fig. 2). terior is also white, but tinged with violet and A vertical or radial rib projects downward and pink (Haderlie and Abbott 1980). anteriorly from hinge in both valves (Siliqua, General Morphology: Bivalve mollusks are Keen and Coan 1974) (Fig. 2). bilaterally symmetrical with two lateral Eyes: valves or shells that are hinged dorsally and Foot: The foot in S. patula projects to a length 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. 2015. Siliqua patula. 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.

that is one half the total shell length and has four, while the Solenidae have a single cardi- a muscular flap (Haderlie and Abbott 1980). nal tooth on each shell valve (Coan and Va- It aids in digging by anchoring within the lentich-Scott 2007). Other local razor-shaped sediment and contracting such that the body clams besides the Solenidae such as the My- is pulled downward (Ricketts and Calvin tiiidae include some genera (e.g. Adula) which 1952) (see Burrow and Behavior). are also long and cylindrical. Adula (see A. Siphons: Siphons are short and fused at californiensis, this guide) are usually a boring the tips, except at the very end (Haderlie species, however, having hairy posterodorsal and Abbott 1980) (Fig. 4). The exhalant and slopes, a very small anterior adductor scar, inhalant openings are ringed by tentacles. and no hinge teeth (Coan and Valentich-Scott Burrow: A fast burrower, S. patula uses its 2007). Hiatellidae, including the geoduck, Pa- foot to anchor and muscular contractions to nopea generosa have large, quadrate, gaping pull body downward. Individuals can com- bivalves, without hinge teeth, and with nearly pletely bury itself within seven seconds equal adductor muscle scars (Keen and Coan (Ricketts and Calvin 1952) and the burrow- 1974). ing speed allows them to avoid the reach of Four species are reported locally in the many clam diggers. Burrowing behavior Pharidae. Siliqua patula has an internal rib leaves a slight dimple in the sand at the sur- that slopes anteriorly, a wide and tapering face (not unlike a thumb imprint). There is posterior end. Siliqua lucida is smaller than no permanent burrow, unlike the similar spe- S. patula (< 55 mm in length) and has an in- cies Solen sicarius (see description in this ternal rib that is vertical and narrow and a guide) (Haderlie and Abbott 1980). Individu- posterior end that is truncate. It has been als orient vertically within the sediment (see suggested that S. lucida are simply young S. Fig 3, Pohlo 1963; Haderlie and Abbott patula individuals (Hertlein 1961), but this is 1980). not yet known. Siliqua lucida lives in protected bay sands and has concentric brown Possible Misidentifications bands on its exterior. Although variations in Solenidae and Pharidae are two ra- S. patula have been synonymized, occasio- zor clam families represented locally and nally readers will find references to S. patula pharid genera were recently placed in the var. nuttallii, which is more oval shape, with former family (see previous editions of this purple beaks and four hinge teeth in the left guide). They are both characterized by cy- valve, not two (Oldroyd 1924). Ensis myrae lindrical shells that are about 2.5 times as and Siliqua altra are offshore species and E. long as high and gape at both ends. They myrae is has a shell that is long and thin. have no dorsal margin ears (compare to Only two species, in the genus Solen, Pectinidae, see Plate 394E, Coan and Va- are reported locally in the Solenidae, they lentich-Scott 2007), a hinge with ligament have an almost straight dorsal margin, a ter- that is entirely external and dorsal, equally minal beak, and one cardinal tooth in each shaped adductor muscle scars (compare to valve (Keen 1971). Solen rostiformis (= S. Mytilus trossulus, this guide), and shells that rosaceus, but see Pohlo 1963; von Cosel do not have prominent radial sculpturing 1992) has a thin shell that tapers and a peri- (Coan and Valentich-Scott 2007). The diffe- ostracum that is lighter than S. sicarius; it is rence between the two families is that mem- light olive green to brown in color. Solen ros- bers of the Pharidae have one shell valve tiformis is a pink shelled clam and its siphons with two cardinal teeth and the other with are annulated (and it can regenerate them

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]

when disturbed, Pohlo 1963). It lives in (Anonymous 1968; Haderlie and Abbott sandier situations than does S. sicarius 1980). This niche is occupied further south by (Coan and Carlton 1975). Solen sicarius, on the Pismo clam, Trivela stultorum (Ricketts the other hand, has a thick shell, a blunt and Calvin 1971). posterior (‘the blunt razor shell’) and a dark Salinity: Collected at salinities of 30 or more, brown periostracum. Solen sicarius is found in full strength seawater. occasionally in permanent burrows in mud Temperature: Lives in cold to temperate wa- or muddy sand (Kozloff 1974) and is the ters. species most likely to be confused with Sili- Tidal Level: Low intertidal to shallow subtidal qua patula. It lacks an interior vertical rib (Haderlie and Abbott 1980), about - 0.3 me- and multiple hinge teeth, and is four times ters and lower (Kozloff 1993). as long as wide, not 2.5 times, as in S. patu- Associates: Known associates include the la (Keen and Coan 1974). Furthermore, the olive snail, Olivella biplicata, caprellid profile in S. patula is much more oval, and amphipods, and polychaetes (e.g., Ophelia). not as cylindrical as in Solen sicarius. The commensal nemertean, Malacobdella One long, cylindrical bivalve of the grossa, occurs in up to 80% of the clams (Fig. family Solecurtidae, Tagelus californianus, 1a) (Ricketts and Calvin 1952; Haderlie and the jackknife clam, could be confused with Abbott 1980). These nemerteans are found Siliqua patula. It too has nearly central attached to the clam’s gills with their posterior beaks, is about 2.5 times as long as wide, sucker and they feed on planktonic organisms and gapes at both ends. It never has the in the water that is passed over the gill internal strengthening rib of S. patula, howe- surface; there is believed to be no harmful ver, and its ligament is seated on a nymph effect (Ricketts and Calvin 1952; Kozloff or projection (as in Protothaca staminea, 1991). see plate). Tagelus californianus is gray, Abundance: Populations can be very abun- has no lateral teeth, and has short siphons dant in certain locals, but they move and fluc- (Coan and Carlton 1975). It is found below tuate, which may be due to sand movement Humboldt Bay, California, in mudflats. from storms and surf. Densest groups occur near mean low water (Anonymous 1968). Up Ecological Information to 10,123 clams/m2 were reported in British Range: Siliqua patula was described from Columbia, Canada (see Table 6, Bourne and individuals collected near Coal Harbor, Cook Quayle). Inlet, Alaska (Weymouth et al. 1926). Known range includes Aleutian Islands to Life-History Information Pismo Beach, California, but individuals are Reproduction: Separate sexes with broad- uncommon in California (Weymouth et al. cast spawning and external fertilization. Fe- 1931). males produce 6–10 million eggs. In Local Distribution: Coos Bay distribution at Washington, all individuals spawn suddenly Pt. Adams spit near the mouth of the bay and simultaneously near the end of May or and usually on open coast. This species is early June, when water temperatures rise more common in coastal regions with long (e.g., 13˚C, Fraser 1936; Ricketts and Calvin stretches of wide sandy beaches (e.g., 1952; Haderlie and Abbott 1980). However, Seaside, OR, Connolly 1995). spawning is not sudden or simultaneous in Habitat: Flat, open beaches with fine, clean Alaska or British Columbia, Canada, where sand in strong surf zone with aeration spawning occurs from July to August (Ricketts

and Calvin 1952; Bourne and Quayle 1970; mature or maturing (Queen Charlotte Island, Breese and Robinson 1981, Lassuy and Fraser 1936). In British Columbia, clams Simons 1989. Sperm morphology appears reached 90 mm by about 1.5–3 years old to characterize many veneroid taxa (see Fig. (Bourne and Quayle 1970). 2, Healy 1995). Longevity: 12 (Washington) to 19 years of Larva: Bivalve development, including age (Alaska) (Ricketts and Calvin 1952; members of the Pholadidae, generally pro- Haderlie and Abbott 1980); little growth is ceeds from external fertilization via broad- seen after 15 years (Alaska, Haderlie and Ab- cast spawning through a ciliated trocho- bott 1980). The largest individuals in Califor- phore stage to a veliger larva. Bivalve veli- nia were nine years old (Haderlie and Abbott gers are characterized by a ciliated velum 1980). Mortality is high among young individ- that is used for swimming, feeding and res- uals (reaching up to 99%), with greatest loss- piration. The veliger larva is also found in es after major storms (Anonymous 1968). many gastropod larvae, but the larvae in the Growth Rate: Growth can be measured by two groups can be recognized by shell mor- annual shell rings; growing seasons show as phology (i.e. snail-like versus clam-like). In wide brown areas between rings. Growth pro- bivalves, the initial shelled-larva is called a D ceeds as follows: 20 mm in first year, 130 -stage or straight-hinge veliger due to the mm after 5 years, and 160 mm after 13 years “D” shaped shell. This initial shell is called a (Haderlie and Abbott 1980). Individuals reach prodissoconch I and is followed by a prodis- 11.5 cm in length by approximately 3.5 years soconch II, or shell that is subsequently add- (Washington). Washington and California ed to the initial shell zone. Finally, shell se- (e.g., Pismo) individuals grow rapidly, but do creted following metamorphosis is simply not reach as large a size or live as long as referred to as the dissoconch (see Fig. 2, they do in Alaska (Chignik Bay, Weymouth et Brink 2001). Once the larva develops a foot, al. 1926; Ricketts and Calvin 1952). Growth usually just before metamorphosis and loss rates tend to slow after 10 cm sizes are of the velum, it is called a pediveliger (see reached (Weymouth and McMillin 1931). Fig. 1, Kabat and O’Foighil 1987; Brink Winter shell lengths were measured in Long 2001). (For generalized life cycle see Fig. 1, Beach, British Columbia, Canada and were Brink 2001.) Swimming larval duration is up 37mm, 91mm, 112.5 mm, 123 mm, and to eight weeks (Ricketts and Calvin 1952; 131mm in years 1–5, respectively (Bourne Haderlie and Abbott 1980). Larvae of Sili- and Quayle 1970). qua patula are free swimming, but they often Food: A filter feeder of planktonic diatoms. stay close to sediment surface (Haderlie and Siliqua patula concentrates phytoplankton Abbott 1980). After metamorphosis, individ- and, at the same time, concentrates some uals are the size of wheat grain or smaller species that are associated with harmful algal and reach to 1.5 cm by end of the “growing blooms (e.g., Pseudo-nitzschia). Toxins season” in December (Washington, Anony- (domioc acid) within their tissues can be dan- mous 1968). gerous if ingested by humans (Horner et al. Juvenile: Juveniles have an oval shell out- 1997; Dortch et al. 1997; Kumar et al. 2009; line until they are about 2.5 mm in length Chadsey et al. 2012). (Pohlo 1963). Individuals are with central Predators: Siliqua patula is probably the beak, but not elongate (see Fig. 6, Pohlo most highly prized food mollusk in the north- 1963). Eighty-six percent of third year clams west, thus this species has been extensively (approximately 10 cm in length) are sexually harvested both recreationally and commer-

cially. Unrestricted in 1925, harvesting se- at Masset, British Columbia. Proceedings verely harmed populations (Weymouth and of the National Shellfisheries Association. McMillin 1931) and lead to a downward 69:21-29. trend. In 1976, Oregon total harvest was 5. BOURNE, N., and D. B. QUAYLE. 1970. 2,211,000 clams (Link 1977). Additional Breeding and growth of razor clams in Brit- predators include seagulls, ducks, perch, ish Columbia. Technical Report of the crab, and fish (e.g. Starry flounder) Fisheries Research Board of Canada. No. (Anonymous 1968; Haderlie and Abbott 232:1-42. 1980). Interestingly, DNA sequence data 6. BREESE, W. P., and A. ROBINSON. revealed that razor clam species in the 1981. Razor clams, Silqua patula (Dixon): commercially harvested genus Ensis are gonadal development, induced spawning often mislabeled as congeneric cryptic and larval rearing. Aquaculture. 22:27-33. species with sympatric distributions 7. BRINK, L. A. 2001. Mollusca: Bivalvia, p. (Esperina et al. 2009; Vierna et al. 2013). 129-149. In: Identification guide to larval Behavior: Siliqua patula is known for its marine invertebrates of the Pacific North- quick, efficient digging (see Burrow). Indi- west. A. Shanks (ed.). Oregon State Uni- viduals move especially rapidly in the sec- versity Press, Corvallis, OR. ond or "slosh" layer of sand (Anonymous 8. CHADSEY, M., V. L. TRAINER, and T. M. 1968). Digging is accomplished by the abil- LESCHINE. 2012. Cooperation of science ity of the anchor-shaped foot to change and management for harmful algal shape. Extraordinary muscle capacity and blooms: domoic acid and the Washington the displacement of body fluids are respon- coast razor clam fishery. Coastal Manage- sible for this (Pohlo 1963; Kozloff 1993). ment. 40:33-54. Digging is vertical, and is sometimes angled 9. COAN, E. V., and P. VALENTICH-SCOTT. toward the sea with very little horizontal 2007. Bivalvia, p. 807-859. In: The Light movement. Individuals 3 to 8 cms in length and Smith manual: intertidal invertebrates bury themselves within 7 and 27 seconds, from central California to Oregon. J. T. respectively (Pohlo 1963). Carlton (ed.). University of California Press, Berkeley, CA. Bibliography 10. CONNOLLY, T. J. 1995. Archaeological 1. ADAMS, N. G., M. LESOING, and V. L. evidence for a former bay at Seaside, Ore- TRAINER. 2000. Environmental condi- gon. Quaternary Research. 43:362-369. tions associated with domoic acid in ra- 11. DIXON, G. 1789. A voyage around the zor clams on the Washington coast. world. George Goulding, London. Journal of Shellfish Research. 19:1007- 12. DORTCH, Q., R. ROBICHAUX, S. POOL, 1015. D. MILSTED, G. MIRE, N. N. RABALAIS, 2. ANONYMOUS. 1968. Invertebrate fisher- T. M. SONIAT, G. A. FRYXELL, R. E. ies, p. 35-49. Department of Fish and TURNER, and M. L. PARSONS. 1997. Wildlife, Oregon State University, Corval- Abundance and vertical flux of Pseudo- lis, OR. nitzschia in the northern Gulf of Mexico. 3. BISHOP, J. A. 2000. A record size for Marine Ecology Progress Series. 146:249- the razor clam Siliqua patula. Festivus. 264. 32:77-78. 13. DRUM, A. S., T. L. SIEBENS, E. A. CRE- 4. BOURNE, N. 1979. Razor clam, Siliqua CELIUS, and R. A. ELSTON. 1993. Do- patula Dixon, breeding and recruitment moic acid in the Pacific razor clam, Silqua

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