Phylum: Mollusca Zirfaea pilsbryi Class: Bivalvia, Heterodonta, Euheterodonta Order: Imparidentia, Myida The rough piddock Family: Pholadoidea, Pholadidae, Pholadinae Taxonomy: The taxonomies of both pholad 2007). Myoid bivalves are burrowers and bor- species in this guide (Z. pilsbryi and Penitel- ers, with long siphons and hinges with few la penita) are extensive and complicated, teeth (Coan and Valentich-Scott 2007). Mem- including many synonyms and overlapping bers of the Pholadidae bore into a variety of descriptions (for full list of synonymies see substrates, possess no pallets on siphon tips Kennedy 1974). Zirfaea pilsbryi was origi- and have an anterior end that is pointed or nally described as Z. gabbii, a species even- curved with no notch (contrast to Teredinidae tually moved to the genus Penitella (see P. species, e.g., Bankia setacea, this guide) (see gabbii, Kennedy 1974). Lowe renamed and Plate 427F, 430D, Coan and Valentich-Scott described Z. pilbsryi in 1931. Thus, these 2007). While most pholad species are inter- three species names (Z. pilsbryi, Z. gabbii, tidal or subtidal, some can be found boring and P. gabbii) and the subspecies designa- into wood at great depths (e.g., 7,250 meters tion, Z. gabbii femii (Adegoke 1967 in Ken- Xylophaga, Kennedy 1974; Reft and Voight nedy 1974), are common synonyms, with 2009; Voight 2009; Marshall and Spencer descriptions that overlap and are specific to 2013). original author (see Kennedy 1974). Body: (see Plate 297, Ricketts and Calvin 1952; Fig 361, Kozloff 1993). Description Color: Size: Individuals up to 150 mm in length Interior: (Ricketts and Calvin 1971; Haderlie and Ab- Exterior: bott 1980; Kozloff 1993) and may be the Byssus: largest of the boring species (Ricketts and Gills: Calvin 1971). Coos Bay (Fossil Point) Shell: Gapes widely at both ends and valves specimens were approximately 75–125 mm have ventral marginal groove (Fig. 2). Anteri- long. or end has rasping ridges, but posterior is with Color: White exterior, interior also white or smooth, concentric lines (Haderlie and Abbott light salmon (Turner 1954; Haderlie and 1980; Kozloff 1993). Anterior end of shell is Abbott 1980). Siphons gray-white to ivory, not as prominently demarcated from the pos- speckled with very small (1.5–2 mm) orange terior (compare to Penitella penita, this guide). chitinous spots, dark red around siphonal Shell is relatively fragile as it gains ample pro- openings and incurrent cirri (Fig. 1). Foot tection from its surrounding burrow (Ricketts and mantle are ivory in color, when and Calvin 1952). preserved (Turner 1954). Periostracum is Interior: The groove separating anteri- dark brown (Haderlie and Abbott 1980). or and posterior sections of valve (or umbonal General Morphology: Bivalve mollusks are ventral sulcus) is conspicuous in juveniles, but bilaterally symmetrical with two lateral almost disappears near ventral margin in valves or shells that are hinged dorsally and older specimens (Kennedy 1974) (Fig. 1). surround a mantle, head, foot and viscera Strong muscle scars present, but no hinge or (see Plate 393B, Coan and Valentich-Scott 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. Zirfaea pilsbryi. 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. ligament (Pholadidae, Quayle 1970). Pallial drical burrow. While burrowing, individuals sinus is broad and deep, extending nearly to exude particles out the inhalant siphon by umbo (Fig. 3). The apophysis (or contracting their body quickly (Ricketts and myophore) is broad, with rounded spoon- Calvin 1952; Haderlie and Abbott 1980). Thir- shaped end (Fig. 3). ty-two movements make for one entire revolu- Exterior: Shape hard, solid, elon- tion, which takes a total of 70 minutes and af- gate, oval, but not globose. Valves divided ter each revolution, the rotating direction alter- into two regions: anterior triangular and pos- nates (MacGinitie in Ricketts and Calvin terior is rounded with concentric rings (Fig. 1952). Burrows may be pear-shaped 1). Anterior is triangular with rough file-like (producing Gastrochaenolites-type traces, radial and concentric denticulations, which Furlong et al. 2014) rather than cone-shaped, can project into spines on anterior margin and individuals often do not fit as tightly within (Fig. 1). Rasping portion covers half total their burrows as other pholads (Evans and valve area (Kozloff 1993). No callum is pre- Fisher 1966). (see also Habitat and Behav- sent (calcareous anterior accessory plate, ior.) see Penitella penita, this guide), only a pro- Pholadidae-specific character tective membrane. Umbonal reflection is Mesoplax: There is only one mesoplax (or wide. The anterior ventral edge of valve is small accessory dorsal plate) present in this strongly angled (Fig. 1). The posterior por- species. It is weak and reduced (Evans and tion is with concentric striations only and is Fisher 1966) and with a transverse basal rounded to truncate (Fig. 1). Gapes extend flange that well-developed in juvenile (Fig. to the middle of the shell (Keen and Coan 4a), but becomes less obvious in adults (Fig. 1974). 4b). (Note: the mesoplax is often lost in col- Hinge: lecting.) Eyes: Foot: Foot is round and truncate (Turner Possible Misidentifications 1954). There are several families of burrow- Siphons: Fused and very long (6–8 times ing clams and the Pholadidae can be distin- the shell length) and can extend 15 cm guished by their distinctively marked body ar- above the burrow surface (Haderlie and Ab- eas. Members of the Teredinidae and Phola- bott 1980). They are non-retractible and didae can be found locally. They can be dis- covered with small chitinous discs, but with- tinguished by the absence of pallets on si- out papillae or pustules. No siphonoplax phon tips in the latter family as well as an an- (flaps around siphon, see Penitella penita, terior end that is not notched, as in the Tere- this guide). Periostracum extends from over dinidae. The Pholadidae includes 10 species 1/3 shell posterior to cover part of siphons locally, within the following genera: Barnea (Quayle 1970). (B. subtruncata), Chaceia (C. ovoidea), Burrow: Zirfaea pilsbryi burrows into heavy Netastoma (N. rostratum), Parapholas (P. cal- mud, clay and shale to 50 cm depths. The ifornica), Penitella (five local species) and foot is sucker-like and attaches to the sub- Zirfaea (Z. pilsbryi). The genus Zirfaea is strate so that the shell can rotate slowly and characterized by adults that burrow into sand create a cylindrical burrow. Shell valves or mud, the absence of a callum in mature in- rock back and forth by contractions of anteri- dividuals, and a shell sculpture that is divided or and posterior adductor muscles. Individu- into two distinct zones (see Plates 427C, als rotate after each stroke, making a cylin- 429D, Coan and Valentich-Scott 2007). The 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] genus Barnea, for example, also lacks a cal- ventral edge, but unlike Zirfaea, P. turnerae lum, but does not have these two distinct has a callum. Penitella richardsoni (=gabbi, zones. All other local genera are character- Kennedy 1989) is also small (up to 75 mm) ized by the presence of a callum and all ex- with a warty, creamy-lemon colored siphon cept Netastoma have a myopore as well. and it is not common. It is different from the Parapholas species have shell sculpture other members of this genus as its umbone with three distinct zones, where members of reflection is not appressed to the anterior end, Chaceia and Pentilla have two. a character also found in C. ovoidea. Penite- The genus closest to Zirfaea, and lla richardsoni differs from C. ovoidea by ha- most likely to be confused with it, is Penitel- ving a callum that does not gap and an more la. As mentioned above, Penitella’s valves elongated shell (Coan and Valentich-Scott are also divided into two distinct sections, 2007). A new species of Penitella, P. hopkin- but it differs in having a calcareous anterior si, was described from Alaska, but it not yet callum, or accessory plate (in the adult) as reported in our area (Kennedy and Armen- well as a posterior which gapes only at the trout 1989). With adult specimens, it should end, not to the middle of the shell (it has no be easy to tell Zirfaea from Penitella by its anterior gape) and the apophysis is narrow, long, non-retractable siphon and by the mem- not broad. No Penitella species has a braneous covering of the anterior, instead of a siphon longer than its body (Evans and calcareous callum. Small shells without the Fisher 1966) and all Penitella species have callum could be young Penitella as well as retractable siphons. There are five species mature Zirfaea and size at maturity varies of Penitella in our area (see Coan and greatly with environmental condition. Valentich-Scott 2007). Zirfaea crispata is a small Atlantic Penitella conradi is very small and is species without chitinous spots on the found in Mytilus or Haliotus (abalone) shells. siphons. It may have been introduced into It has a siphonoplax lined with coarse granu- Humboldt Bay, California with eastern oyster les (Zirfaea has no siphonoplax) (Evans and spat Crassostrea (Turner 1954), but is not Fisher 1966) and can bore into nephrite currently included in local intertidal guides (Monterey, California, Wilson and Kennedy (see Coan and Valentich-Scott 2007).