Entodesma Navicula Class: Bivalvia, Heterodonta, Euheterodonta

Entodesma navicula Class: Bivalvia, Heterodonta, Euheterodonta

Order: Anomalodesmata The rock-dwelling entodesma Family: Pandoroidea, Lyonsiidae

Taxonomy: The Anomalodesmata is a well Color: Shell exterior is white, but also bears supported monophyletic group of bivalves abundant brown color, and transversely stria- that has previously been regarded as a sub- ted periostracum. The shell interior is pink class (e.g., Coan and Scoot 1997; Dreyer et and nacreous (i.e., pearly). al. 2003), however, recently authors suggest General Morphology: Bivalve mollusks are it should no longer be designated as such bilaterally symmetrical with two lateral valves and, instead, be included as a basal lineage or shells that are hinged dorsally and sur- of the Heterodonta (Harper et al. 2006; Hea- round a mantle, head, foot and viscera (see ly et al. 2008). The generic designations Plate 393B, Coan and Valentich-Scott 2007). within the Lyonsiidae have also been un- The Pholadomyoida are characterized by a clear historically, including as few as one shell that has nacreous interior and inconspic- and as many as twelve genera (Prezant uous hinge teeth (if present at all). The Ly- 1980,1981b). Lyonsiid subgeneric and spe- onsiidae are unique among the, exclusively cific designations are often based on varia- marine, group Anomalodesmata due to their ble characters (e.g., periostracal color, shell attachment to hard surfaces with byssal shape and sculpture) leading to several syn- threads (Dreyer et al. 2003; Harper et al. onyms and subgenera that were abandoned 2005). Entodesma species are distinct within altogether by Prezant (1980, 1981b). En- the Lyonsiidae in their habit to attach to rocks todesma navicula has been referred to by its and nestle into crevices. This behavior ren- junior synonym, Entodesma saxicola (Yonge ders their shells thick and of variable shape, 1976; Haderlie 1980; Prezant 1981b; Harper and their byssus strong (Prezant 1981b, et al. 2009 and references therein) due to its 1981c). morphological similarity to a species de- Body: Broadly rounded externally, and with scribed from Japan with an older name. thick shell and variable morphology. The left Based on taxonomic priority (Coan and valve often larger and extending longer than Scott 1997; Harper et al. 2009). Entodesma right (Lyonsiidae, Prezant 1981b). (See Fig. navicula was originally described in the ge- 1, Morton 1981 for external anatomy (as E. nus Lyonsia, but was later transferred to En- saxicola) and Fig. 13, Prezant 1981b for gen- todesma, a genus designated in 1845 by eral internal anatomy of Entodesma species) Philippi. Color: Interior: Ligament is internal Description (Lyonsiidae, Coan and Valentich-Scott 2007), Size: Lyonsiidae is a very large bivalve fami- small, extends ventrally, and is reinforced with ly (Oldroyd 1924) and Entodesma navicula a large lithodesma or ossicle, which is a cal- is one of the largest species within it, with careous plate (Fig. 3) (see Fig. 1, Yonge individuals reaching 150 mm in length 1976). The lithodesma is only found in mem- (Quayle 1970). The illustrated specimen bers of the Anomalodesmata and, it has been (from Coos Bay) is only 60 mm in length and suggested, that its presence allows for the ca- 40 mm in width.

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. Entodesma navicula. 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.

pacity for greater shell width, especially thus, the shell interior in E. navicula is pearly among the Lyonsiidae (Yonge 1976). The and iridescent. The pallial line is also solid lithodesma is particularly large among the and not in patches (Coan and Valentich-Scott Entodesma (Prezant 1981b). A secondary 2007), and the pallial sinus is obscure and an- dorsal ligament is sometimes observed in gular (Oldroyd 1924) (Fig. 3). The two adduc- members of the Lyonsiidae (see Yonge tor muscle scars are conspicuous (Prezant 1976). Internal anatomy is described in de- 1981b) and of equal size (although anterior tail by Morgan and Allen (as E. saxicola, may be slightly smaller than posterior, see 1976). Prezant 1981b), but differ is shape (Fig. 3). Exterior: The shell microstructure is distinct in lyonsiid Byssus: Uses byssal threads to at- bivalves and is described for E. navicula by tach to substratum (e.g., floats, pilings, Harper et al. (2009) as homogeneous, allow- rock). Members of the Entodesma often ing for some shell flexibility to adapt to varying have a byssal notch at the ventral posterior substrates (Prezant 1980, 1981b, 1981c; Har- shell edge (Morgan and Allen 1976; Prezant per et al. 2009). 1981b). Byssal gland is located in the Foot Exterior: The exterior is rough, with and produces very strong byssal threads concentric striations, and coarse or irregular (Morgan and Allen 1976; Prezant 1981b). ribs (Keen and Coan 1974), but not radial Entodesma navicula possesses a single pair ribs. The ventral margins flex, and gape and of byssal muscles, posteriorly, compared to the left valve is slightly larger than right other byssally attached bivalves (e.g., Myti- (Oldroyd 1924). The shell is brittle and lus) that posses three pairs (Morgan and Al- breaks easily. Periostracum covers the shell len 1976). exterior and is coarse and often cracks the Gills: Large gills are deeply plicate shell as it dries, which can be prevented in (i.e., folded) and comprise approximately collecting by applying a lubricant like Vaseline 230 plicae (Morgan and Allen 1976). (Keen 1971). Shell: Overall shell shape is oblong, with Hinge: No true teeth or chondrophore valves longer than they are tall, and shells present (Fig. 3). The beaks are large, in- can be strongly deformed due to nestling curved (Oldroyd 1924), and close to anterior habit. The posterior is gaping and trunca- end (Fig. 2). The umbones do not touch ted. The genus Entodesma contains the thi- (Keen and Coan 1974) (Fig. 2). ckest shelled species within the family Lyon- Eyes: Entodesma species lack photorecep- siidae. Entodesma and Lyonsia species ha- tors (Prezant 1981b). ve the capacity to adhere particles to their Foot: Due to their habit of attaching to various shell exterior, due to the presence of areno- substrata, the foot is reduced, small, and cy- philic radial mantle glands along the mantle lindrical (Entodesma, Morgan and Allen 1976; edge (see Juvenile) (Morgan and Allen Prezant 1981b). The foot is not used for loco- 1976; Yonge 1976; Prezant 1981b, 1981d; motion in E. navicula such that it resembles Lutaenko 2012). Periostracum may extend Mytilus species (Morgan and Allen 1976). beyond the shell edges (up to 1 cm, Morgan Siphons: Siphons are short and muscular and Allen 1976) and bear radial striations (Prezant 1981b), but not red-tipped (compare (Prezant 1981b). to Hiatella arctica description in this guide). Interior: (see Fig. 1, Morgan and Al- Burrow: Individuals do not create a burrow len 1976.) All lynosiids have shell interior per se, but are often nestled into the aban- that is nacreous (Morgan and Allen 1976),

doned burrows of other invertebrates (e.g., Representatives of each genera occur locally, pholads). including Mytilimeria nuttallii, Lyonsia californica, Entodesma pictum (= E. inflatum), Possible Misidentifications and E. navicula (= E. saxicola). Entodesma There are five bivalve subclasses navicula have a thick shell and anterior end based on morphology and fossil evidence that is one third the total shell length as well and one of those is the diverse Heterodonta. as a heavy periostracum. Entodesma pictum, The monophyletic group Anomalodestmata on the other hand, has a thin shell, thin comprises at least one sixth of all bivalves periostracum and an anterior end that is less families (Harper et al. 2006), which are than one third the total length. The shell of E. widely diverse and found in specific marine pictum is also smaller, lighter in color and niches (Morgan 1981). They are character- more regular in shape than E. navicula. The ized by a nacreous shell, a ligament with a shell shape in Entodesma species is irregular lithodesma (ossicle), as well as a variety of due to their nestling habits and attachment to characters of internal anatomy (see Dreyer the substratum. Mytilimeria nuttallii has a et al. 2003). Family designations within this circular shell outline. In Lyonsia californica, group have been difficult to interpret taxo- the shell and periostracum are is thin and nomically due to the extreme variation in elongate with a conspicuous posterior end morphology and life habits of groups (see (Pimenta and Oliveira 2013). The latter Fig. 2, Harper et al. 2006; Healy et al. 2008). species tends to occur in protected muddy Three bivalve families including the, bays and the former in the rocky intertidal potentially diphyletic (see Dreyer et al. 2003) among ascidians (e.g. Cystodites, Kabat and Lyonsiidae, Hiatellidae, and Thraciidae are O’Foighil 1987; Harper et al. 2009). characterized by their lack of dorsal margin Of the nestling or burrowing clams of ears or projecting teeth or chondrophores, our estuarine rocky intertidal, most of the and two adductor muscles. In thraciids the pholads can be immediately distinguished ligament can be both internal and external from Entodesma by their file-like and the pallial line is continuous; in hiatellids denticulations anteriorly, and by the two (see Hiatella arctica in this guide) the liga- distinct sections of each valve (see Penitella ment is always external and the pallial line is penita, Zirfaea pilsbryi in this guide). The broken into patches (see below). On the nestling habit of some clams can distort shell other hand, in the lyonisiids the pallial line is shape and make identification difficult (see continuous, as in thraciids, but the ligament Protothaca staminea in this guide). is always internal, unlike thraciid species Species from other bivalve families that (Coan and Valentich-Scott 2007). may be confused with E. navicula include Hia- The Lyonsiidae is a distinct family tella arctica, Petricola carditoides, and Platyo- consisting up to 45 species comprising three don cancellatus. Hiatella arctica (=Saxicava) genera (Lyonsia, Entodesma, Mytilimeria), is a very similar, often deformed nestling with the latter two having evolved from a Ly- clam. It can be most easily distinguished from onsia-like ancestor (Prezant 1981a, 1981b; E. navicula by its white, porcelain-like interior Harper et al. 2009). (For characters with (Keen and Coan 1974) (not pink and pearly), which to differentiate these genera, see and by its broken pallial line (see Plate 429B, Prezant 1981b and 1981c) Entodesma Coan and Valentich-Scott 2007). It also has species bear the thickest shell among these very distinctive red-tipped siphons (Kozloff three genera (Prezant 1981c). 1993), which are not found in E. navicula. Pe-

tricola carditoides has an external ligament lodesmata are believed to be hermaphroditic and 2–3 cardinal hinge teeth, as well as (Healy et al. 2008). Entodesma navicula is a some radial sculpture, and lives in pholad hermaphroditic species, with external fertiliza- burrows. It is chalky white, with purple- tion and planktonic larvae. Eggs and sperm tipped siphons (Kozloff 1993), and usually is are emitted alternatively (Quayle 1970). Alt- narrower posteriorly than anteriorly. A myid hough the development of this species has clam, Platyodon cancellatus, is another rock not been described, other members of the dweller, but it is a burrower, not a nestler Anomalodesmata are free-spawners, primarily (Quayle 1970; Coan and Valentich-Scott in summer months. These include Lyonsia 2007). It has a chondrophore and tooth in bracteata, which is a simultaneous hermaph- its hinges, fine, almost lamellar concentric rodite with oocytes that are 120 µm and sur- exterior sculpture, and a white interior with a rounded by a thick egg jelly; Mytilimeria nut- well-developed pallial sinus (Kozloff 1974). tallii, is also a simultaneous hermaphrodite Juveniles of the families Clavagelli- that free-spawns in July with oocytes that are dae and Penicillidae (“watering pot bi- also 120 µm in diameter (Kabat and O’Foighil valves”) are morpholgically similar to mem- 1987). The sperm morphology of the family bers of the Lyonsiidae (Morton 2007). Lyonsiidae is of modified (or elongated) morphology (see Fig. 6, Healy et al. 2008). Ova Ecological Information have been observed within the suprabranchial Range: Type locality is Vancouver Island, chamber of the gills in several Entodesma British Columbia (as E. saxicola, Dall 1916). species and larvae have a short pelagic dura- Known range extends in the north Pacific in tion (Prezant 1981b). the Kurile Islands and northern Japan down Larva: Larval development has not been de- through the Aleutian Islands in Alaska to scribed for E. navicula. San Diego, California (Harper et al. 2009). Juvenile: Local Distribution: Local distribution in- Longevity: Arenophilic mantle glands (which cludes sites in Coos Bay, including Fossil produce a secretion that allows for material to Point. be adhered to shell surface, over the peri- Habitat: Occurs among rocks and in crevic- ostracum, Morton 1987) are often present in es and abandoned pholad burrows. Individ- juvenile Entodesma species, but these are uals also found attached by byssus to floats usually lost by adulthood, shell thickness in- and pilings. creases (Prezant 1981b). These glands de- Salinity: Collected at salinities of 30. velop within the mantle, but the specific loca- Temperature: tion has been debated (either the outer fold Tidal Level: Intertidal and subtidal to 60, or (Prezant 1981c, 1981d) or the middle and in- even 82 meters deep (Keen and Coan 1974; ner folds (Morton 1987)), and secrete shell Harper et al. 2009). through the periostracum. Associates: Co-occurs with other nestling Growth Rate: and burrowing molluscs (e.g., Hiatella, Food: A suspension feeder. Ciliary currents Zirfaea, Penitella). move water across gills and all incoming parti- Abundance: Common in Puget Sound, cles move toward the ventral margin of the Washington. Individuals are present, but not inner demibranch before they move anteriorly common, in Oregon (Quayle 1970). to the mouth (Yonge 1952; see Fig. 4, Morgan Life-History Information and Allen 1976). Reproduction: All members of the Anoma- Predators: 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]

Behavior: Individuals adapt to their particu- 8. HEALY, J. M., R. BIELER, and P. M. MIK- lar rocky niche by changing shell shape with KELSEN. 2008. Spermatozoa of the grows, leading to shells with highly irregular Anomalodesmata (Bivalvia, Mollusca) with morphology. special reference to relationships within the group. Acta Zoologica. 89:339-350. Bibliography 9. KABAT, A. R., and D. O'FOIGHIL. 1987. 1. BRINK, L. A. 2001. Mollusca: Bivalvia, p. Phylum Mollusca, Class Bivalvia, p. 309- 129-149. In: Identification guide to larval 353. In: Reproduction and development of marine invertebrates of the Pacific North- marine invertebrates of the northern Pacif- west. A. Shanks (ed.). Oregon State Uni- ic Coast. M. F. Strathmann (ed.). Universi- versity Press, Corvallis, OR. ty of Washington Press, Seattle, WA. 2. COAN, E. V., and P. H. SCOTT. 1997. 10. KEEN, A. M. 1971. Sea shells of tropical Checklist of the marine bivalves of the west America: marine mollusks from Baja northeastern Pacific Ocean. Santa Bar- California to Peru. Stanford University bara Museum of Natural History Contri- Press, Stanford, CA. butions in Science. 1:1-28. 11. KEEN, A. M., and E. COAN. 1974. Marine 3. COAN, E. V., and P. VALENTICH- molluscan genera of western North Ameri- SCOTT. 2007. Bivalvia, p. 807-859. In: ca: an illustrated key. Stanford University The Light and Smith manual: intertidal Press, Stanford, CA. invertebrates from central California to 12. KOZLOFF, E. N. 1974. Keys to the marine Oregon. J. T. Carlton (ed.). University of invertebrates of Puget Sound, the San California Press, Berkeley, CA. Juan Archipelago, and adjacent regions. 4. DALL, W. H. 1916. A review of some bi- University of Washington Press, Seattle. valve shells of the group Anatinacea 13. —. 1993. Seashore life of the northern Pa- from the west coast of America. Pro- cific coast: an illustrated guide to northern ceedings of the United States National California, Oregon, Washington, and Brit- Museum. 49:441-456. ish Columbia. University of Washington 5. DREYER, H., G. STEINER, and E. M. Press, Seattle. HARPER. 2003. Molecular phylogeny of 14. LUTAENKO, K. A. 2012. Transportation of Anomalodesmata (Mollusca : Bivalvia) bivalve shells with attached algae in Us- inferred from 18S rRNA sequences. Zoo- suriysky Bay (Sea of Japan). Byulleten' logical Journal of the Linnean Society. Dal'nevostochnogo Malakologicheskogo 139:229-246. Obshchestva. 15-1:154-164. 6. HARPER, E. M., A. G. CHECA, and A. 15. MORGAN, R. E., and J. A. ALLEN. 1976. B. RODRIGUEZ-NAVARRO. 2009. Or- On the functional morphology and adapta- ganization and mode of secretion of the tions of Entodesma saxicola (Bivalvia, granular prismatic microstructure of En- Anomalodesmacea). Malacologia. 15:233- todesma navicula (Bivalvia: Mollusca). 240. Acta Zoologica. 90:132-141. 16. MORTON, B. 1981. The Anomalodesma- 7. HARPER, E. M., H. DREYER, and G. ta. Malacologia. 21:35-60. STEINER. 2006. Reconstructing the 17. —. 1987. The mantle margin and radial Anomalodesmata (Mollusca : Bivalvia): mantle glands of Entodesma saxicola and morphology and molecules. Zoological Entodesma inflata (Bivalvia, Anoma- Journal of the Linnean Society. 148:395- lodesmata, Lyonsiidae). Journal of Mollus- 420. can Studies. 53:139-151.

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