Entodesma Navicula Class: Bivalvia, Heterodonta Order: Pholadomyoida/ Anomalodesmata the Rock-Dwelling Entodesma Family: Lyonsiidae

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Phylum: Mollusca Entodesma navicula Class: Bivalvia, Heterodonta Order: Pholadomyoida/ Anomalodesmata The rock-dwelling entodesma Family: Lyonsiidae

Taxonomy: The Anomalodesmata is a well surround a mantle, head, foot and viscera supported monophyletic group of bivalves that (see Plate 393B, Coan and Valentich-Scott has previously been regarded as a subclass 2007). The Pholadomyoida are characterized (e.g., Coan and Scoot 1997; Dreyer et al. by a shell that has nacreous interior and 2003), however, recently authors suggest it inconspicuous hinge teeth (if present at all). should no longer be designated as such and, The Lyonsiidae are unique among the, instead, be included as a basal lineage of the exclusively marine, group Anomalodesmata Heterodonta (Harper et al. 2006; Healy et al. due to their attachment to hard surfaces with 2008). The generic designations within the byssal threads (Dreyer et al. 2003; Harper et Lyonsiidae have also been unclear al. 2005). Entodesma species are distinct historically, including as few as one and as within the Lyonsiidae in their habit to attach to many as twelve genera (Prezant rocks and nestle into crevices. This behavior 1980,1981b). Lyonsiid subgeneric and renders their shells thick and of variable specific designations are often based on shape, and their byssus strong (Prezant variable characters (e.g., periostracal color, 1981b, 1981c). shell shape and sculpture) leading to several Body: Broadly rounded externally, and with synonyms and subgenera that were thick shell and variable morphology. The left abandoned altogether by Prezant (1980, valve often larger and extending longer than 1981b). Entodesma navicula has been right (Lyonsiidae, Prezant 1981b). (See Fig. referred to by its junior synonym, Entodesma 1, Morton 1981 for external anatomy (as E. saxicola (Yonge 1976; Haderlie 1980; Prezant saxicola) and Fig. 13, Prezant 1981b for 1981b; Harper et al. 2009 and references general internal anatomy of Entodesma therein) due to its morphological similarity to a species) species described from Japan with an older Color: name. Based on taxonomic priority (Coan and Interior: Ligament is internal Scott 1997; Harper et al. 2009). Entodesma (Lyonsiidae, Coan and Valentich-Scott 2007), navicula was originally described in the genus small, extends ventrally, and is reinforced with Lyonsia, but was later transferred to a large lithodesma or ossicle, which is a Entodesma, a genus designated in 1845 by calcareous plate (Fig. 3) (see Fig. 1, Yonge Philippi. 1976). The lithodesma is only found in members of the Anomalodesmata and, it has Description been suggested, that its presence allows for Size: Lyonsiidae is a very large bivalve family the capacity for greater shell width, especially (Oldroyd 1924) and Entodesma navicula is among the Lyonsiidae (Yonge 1976). The one of the largest species within it, with lithodesma is particularly large among the individuals reaching 150 mm in length Entodesma (Prezant 1981b). A secondary (Quayle 1970). The illustrated specimen dorsal ligament is sometimes observed in (from Coos Bay) is only 60 mm in length and members of the Lyonsiidae (see Yonge 40 mm in width. 1976). Internal anatomy is described in detail Color: Shell exterior is white, but also bears by Morgan and Allen (as E. saxicola, 1976). abundant brown color, and transversely Exterior: striated periostracum. The shell interior is Byssus: Uses byssal threads to pink and nacreous (i.e., pearly). attach to substratum (e.g., floats, pilings, General Morphology: Bivalve mollusks are rock). Members of the Entodesma often have bilaterally symmetrical with two lateral valves a byssal notch at the ventral posterior shell or shells that are hinged dorsally and edge (Morgan and Allen 1976; Prezant

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12747 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] 1981b). Byssal gland is located in the Foot exterior and is coarse and often cracks the and produces very strong byssal threads shell as it dries, which can be prevented in (Morgan and Allen 1976; Prezant 1981b). collecting by applying a lubricant like Vaseline Entodesma navicula possesses a single pair (Keen 1971). of byssal muscles, posteriorly, compared to Hinge: No true teeth or chondrophore other byssally attached bivalves (e.g., Mytilus) present (Fig. 3). The beaks are large, that posses three pairs (Morgan and Allen incurved (Oldroyd 1924), and close to anterior 1976). end (Fig. 2). The umbones do not touch Gills: Large gills are deeply plicate (Keen and Coan 1974) (Fig. 2). (i.e., folded) and comprise approximately 230 Eyes: Entodesma species lack plicae (Morgan and Allen 1976). photoreceptors (Prezant 1981b). Shell: Overall shell shape is oblong, with Foot: Due to their habit of attaching to valves longer than they are tall, and shells various substrata, the foot is reduced, small, can be strongly deformed due to nestling and cylindrical (Entodesma, Morgan and Allen habit. The posterior is gaping and truncated. 1976; Prezant 1981b). The foot is not used The genus Entodesma contains the thickest for locomotion in E. navicula such that it shelled species within the family Lyonsiidae. resembles Mytilus species (Morgan and Allen Entodesma and Lyonsia species have the 1976). capacity to adhere particles to their shell Siphons: Siphons are short and muscular exterior, due to the presence of arenophilic (Prezant 1981b), but not red-tipped (compare radial mantle glands along the mantle edge to Hiatella arctica description in this guide). (see Juvenile) (Morgan and Allen 1976; Burrow: Individuals do not create a burrow Yonge 1976; Prezant 1981b, 1981d; per se, but are often nestled into the Lutaenko 2012). Periostracum may extend abandoned burrows of other invertebrates beyond the shell edges (up to 1 cm, Morgan (e.g., pholads). and Allen 1976) and bear radial striations (Prezant 1981b). Possible Misidentifications Interior: (see Fig. 1, Morgan and There are five bivalve subclasses Allen 1976.) All lynosiids have shell interior based on morphology and fossil evidence and that is nacreous (Morgan and Allen 1976), one of those is the diverse Heterodonta. The thus, the shell interior in E. navicula is pearly monophyletic group Anomalodestmata and iridescent. The pallial line is also solid comprises at least one sixth of all bivalves and not in patches (Coan and Valentich-Scott families (Harper et al. 2006), which are widely 2007), and the pallial sinus is obscure and diverse and found in specific marine niches angular (Oldroyd 1924) (Fig. 3). The two (Morgan 1981). They are characterized by a adductor muscle scars are conspicuous nacreous shell, a ligament with a lithodesma (Prezant 1981b) and of equal size (although (ossicle), as well as a variety of characters of anterior may be slightly smaller than posterior, internal anatomy (see Dreyer et al. 2003). see Prezant 1981b), but differ is shape (Fig. Family designations within this group have 3). The shell microstructure is distinct in been difficult to interpret taxonomically due to lyonsiid bivalves and is described for E. the extreme variation in morphology and life navicula by Harper et al. (2009) as habits of groups (see Fig. 2, Harper et al. homogeneous, allowing for some shell 2006; Healy et al. 2008). flexibility to adapt to varying substrates Three bivalve families including the, (Prezant 1980, 1981b, 1981c; Harper et al. potentially diphyletic (see Dreyer et al. 2003) 2009). Lyonsiidae, Hiatellidae, and Thraciidae are Exterior: The exterior is rough, with characterized by their lack of dorsal margin concentric striations, and coarse or irregular ears or projecting teeth or chondrophores, and ribs (Keen and Coan 1974), but not radial two adductor muscles. In thraciids the ribs. The ventral margins flex, and gape and ligament can be both internal and external and the left valve is slightly larger than right the pallial line is continuous; in hiatellids (see (Oldroyd 1924). The shell is brittle and Hiatella arctica in this guide) the ligament is breaks easily. Periostracum covers the shell always external and the pallial line is broken

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. into patches (see below). On the other hand, distinguished from E. navicula by its white, in the lyonisiids the pallial line is continuous, as porcelain-like interior (Keen and Coan 1974) in thraciids, but the ligament is always internal, (not pink and pearly), and by its broken pallial unlike thraciid species (Coan and Valentich- line (see Plate 429B, Coan and Valentich- Scott 2007). Scott 2007). It also has very distinctive red- The Lyonsiidae is a distinct family tipped siphons (Kozloff 1993), which are not consisting up to 45 species comprising three found in E. navicula. Petricola carditoides genera (Lyonsia, Entodesma, Mytilimeria), with has an external ligament and 2–3 cardinal the latter two having evolved from a Lyonsia- hinge teeth, as well as some radial sculpture, like ancestor (Prezant 1981a, 1981b; Harper et and lives in pholad burrows. It is chalky al. 2009). (For characters with which to white, with purple-tipped siphons (Kozloff differentiate these genera, see Prezant 1981b 1993), and usually is narrower posteriorly and 1981c) Entodesma species bear the than anteriorly. A myid clam, Platyodon thickest shell among these three genera cancellatus, is another rock dweller, but it is a (Prezant 1981c). Representatives of each burrower, not a nestler (Quayle 1970; Coan genera occur locally, including Mytilimeria and Valentich-Scott 2007). It has a nuttallii, Lyonsia californica, Entodesma pictum chondrophore and tooth in its hinges, fine, (= E. inflatum), and E. navicula (= E. saxicola). almost lamellar concentric exterior sculpture, Entodesma navicula have a thick shell and and a white interior with a well-developed anterior end that is one third the total shell pallial sinus (Kozloff 1974). length as well as a heavy periostracum. Juveniles of the families Clavagellidae Entodesma pictum, on the other hand, has a and Penicillidae (“watering pot bivalves”) are thin shell, thin periostracum and an anterior morpholgically similar to members of the end that is less than one third the total length. Lyonsiidae (Morton 2007). The shell of E. pictum is also smaller, lighter in color and more regular in shape than E. Ecological Information navicula. The shell shape in Entodesma Range: Type locality is Vancouver Island, species is irregular due to their nestling habits British Columbia (as E. saxicola, Dall 1916). and attachment to the substratum. Mytilimeria Known range extends in the north Pacific in nuttallii has a circular shell outline. In Lyonsia the Kurile Islands and northern Japan down californica, the shell and periostracum are is through the Aleutian Islands in Alaska to San thin and elongate with a conspicuous posterior Diego, California (Harper et al. 2009). end (Pimenta and Oliveira 2013). The latter Local Distribution: Local distribution species tends to occur in protected muddy includes sites in Coos Bay, including Fossil bays and the former in the rocky intertidal Point. among ascidians (e.g. Cystodites, Kabat and Habitat: Occurs among rocks and in crevices O’Foighil 1987; Harper et al. 2009). and abandoned pholad burrows. Individuals Of the nestling or burrowing clams of also found attached by byssus to floats and our estuarine rocky intertidal, most of the pilings. pholads can be immediately distinguished Salinity: Collected at salinities of 30. from Entodesma by their file-like Temperature: denticulations anteriorly, and by the two Tidal Level: Intertidal and subtidal to 60, or distinct sections of each valve (see Penitella even 82 meters deep (Keen and Coan 1974; penita, Zirfaea pilsbryi in this guide). The Harper et al. 2009). nestling habit of some clams can distort shell Associates: Co-occurs with other nestling shape and make identification difficult (see and burrowing molluscs (e.g., Hiatella, Protothaca staminea in this guide). Zirfaea, Penitella). Species from other bivalve families Abundance: Common in Puget Sound, that may be confused with E. navicula include Washington. Individuals are present, but not Hiatella arctica, Petricola carditoides, and common, in Oregon (Quayle 1970). Platyodon cancellatus. Hiatella arctica (=Saxicava) is a very similar, often deformed nestling clam. It can be most easily

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12747 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Life-History Information Bibliography Reproduction: All members of the Anomalodesmata are believed to be 1. BRINK, L. A. 2001. Mollusca: Bivalvia, hermaphroditic (Healy et al. 2008). p. 129-149. In: Identification guide to Entodesma navicula is a hermaphroditic larval marine invertebrates of the species, with external fertilization and Pacific Northwest. A. Shanks (ed.). planktonic larvae. Eggs and sperm are Oregon State University Press, emitted alternatively (Quayle 1970). Although Corvallis, OR. the development of this species has not been 2. COAN, E. V., and P. H. SCOTT. 1997. described, other members of the Checklist of the marine bivalves of the Anomalodesmata are free-spawners, primarily northeastern Pacific Ocean. Santa in summer months. These include Lyonsia Barbara Museum of Natural History bracteata, which is a simultaneous Contributions in Science. 1:1-28. hermaphrodite with oocytes that are 120 µm 3. COAN, E. V., and P. VALENTICH- and surrounded by a thick egg jelly; SCOTT. 2007. Bivalvia, p. 807-859. In: Mytilimeria nuttallii, is also a simultaneous The Light and Smith manual: intertidal hermaphrodite that free-spawns in July with invertebrates from central California to oocytes that are also 120 µm in diameter Oregon. J. T. Carlton (ed.). University (Kabat and O’Foighil 1987). The sperm of California Press, Berkeley, CA. morphology of the family Lyonsiidae is of 4. DALL, W. H. 1916. A review of some modified (or elongated) morphology (see Fig. bivalve shells of the group Anatinacea 6, Healy et al. 2008). Ova have been from the west coast of America. observed within the suprabranchial chamber Proceedings of the United States of the gills in several Entodesma species and National Museum. 49:441-456. larvae have a short pelagic duration (Prezant 5. DREYER, H., G. STEINER, and E. M. 1981b). HARPER. 2003. Molecular phylogeny Larva: Larval development has not been of Anomalodesmata (Mollusca : described for E. navicula. Bivalvia) inferred from 18S rRNA Juvenile: sequences. Zoological Journal of the Longevity: Arenophilic mantle glands (which Linnean Society. 139:229-246. produce a secretion that allows for material to 6. HARPER, E. M., A. G. CHECA, and A. be adhered to shell surface, over the B. RODRIGUEZ-NAVARRO. 2009. periostracum, Morton 1987) are often present Organization and mode of secretion of in juvenile Entodesma species, but these are the granular prismatic microstructure usually lost by adulthood, shell thickness of Entodesma navicula (Bivalvia: increases (Prezant 1981b). These glands Mollusca). Acta Zoologica. 90:132- develop within the mantle, but the specific 141. location has been debated (either the outer 7. HARPER, E. M., H. DREYER, and G. fold (Prezant 1981c, 1981d) or the middle and STEINER. 2006. Reconstructing the inner folds (Morton 1987)), and secrete shell Anomalodesmata (Mollusca : through the periostracum. Bivalvia): morphology and molecules. Growth Rate: Zoological Journal of the Linnean Food: A suspension feeder. Ciliary currents Society. 148:395-420. move water across gills and all incoming 8. HEALY, J. M., R. BIELER, and P. M. particles move toward the ventral margin of MIKKELSEN. 2008. Spermatozoa of the inner demibranch before they move the Anomalodesmata (Bivalvia, anteriorly to the mouth (Yonge 1952; see Fig. Mollusca) with special reference to 4, Morgan and Allen 1976). relationships within the group. Acta Predators: Zoologica. 89:339-350. Behavior: Individuals adapt to their particular 9. KABAT, A. R., and D. O'FOIGHIL. rocky niche by changing shell shape with 1987. Phylum Mollusca, Class grows, leading to shells with highly irregular Bivalvia, p. 309-353. In: Reproduction morphology. and development of marine

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. invertebrates of the northern Pacific 19. OLDROYD, I. S. 1924. Marine shells Coast. M. F. Strathmann (ed.). of Puget Sound and vicinity. University University of Washington Press, of Washington Press, Seattle. Seattle, WA. 20. PIMENTA, A. D., and C. D. DE 10. KEEN, A. M. 1971. Sea shells of CASTRO OLIVEIRA. 2013. tropical west America: marine Taxonomic review of the genus mollusks from Baja California to Peru. Lyonsia (Pelecypoda: Lyonsiidae) Stanford University Press, Stanford, from east coast of South America, with CA. description of a new species and 11. KEEN, A. M., and E. COAN. 1974. notes on other western Atlantic Marine molluscan genera of western species. American Malacological North America: an illustrated key. Bulletin. 31:75-84. Stanford University Press, Stanford, 21. PREZANT, R. S. 1980. Taxonomic CA. revisions of marine Lyonsiidae 12. KOZLOFF, E. N. 1974. Keys to the bivalvia. Bulletin of the American marine invertebrates of Puget Sound, Malacological Union. 46:75-75. the San Juan Archipelago, and 22. —. 1981a. Arenophilic mantle glands, adjacent regions. University of shell ultrastructure, taxonomy, and Washington Press, Seattle. evolution of the Lyonsiidae (Bivalvia: 13. —. 1993. Seashore life of the northern Anomalodesmata). Vol. Ph.D. Pacific coast: an illustrated guide to University of Delaware. northern California, Oregon, 23. —. 1981b. Comparative shell Washington, and British Columbia. ultrasturcture of Lyonsiid bivalves. University of Washington Press, Veliger. 23:289-299. Seattle. 24. —. 1981c. Taxonomic re-evaluation of 14. LUTAENKO, K. A. 2012. the bivalve family Lyonsiidae. Nautilus. Transportation of bivalve shells with 95:58-72. attached algae in Ussuriysky Bay (Sea 25. —. 1981d. The Arenophilic radial of Japan). Byulleten' mantle glands of the Lyonsiidae Dal'nevostochnogo (Bivalvia, Anomalodesmata) with Malakologicheskogo Obshchestva. 15- notes on Lyonsiid evolution. 1:154-164. Malacologia. 20:267-289. 15. MORGAN, R. E., and J. A. ALLEN. 26. QUAYLE, D. B. 1970. The intertidal 1976. On the functional morphology bivalves of British Columbia. British and adaptations of Entodesma Columbia Provincial Museum, Victoria, saxicola (Bivalvia, BC, Canada. Anomalodesmacea). Malacologia. 27. RICKETTS, E. F., and J. CALVIN. 15:233-240. 1952. Between Pacific tides: an 16. MORTON, B. 1981. The account of the habits and habitats of Anomalodesmata. Malacologia. 21:35- some five hundred of the common, 60. conspicuous seashore invertebrates of 17. —. 1987. The mantle margin and the Pacific Coast between Sitka, radial mantle glands of Entodesma Alaska, and Northern Mexico. Stanford saxicola and Entodesma inflata University Press, Stanford. (Bivalvia, Anomalodesmata, 28. YONGE, C. M. 1976. Primary and Lyonsiidae). Journal of Molluscan secondary ligaments with the Studies. 53:139-151. Lithodesma in the Lyonsiidae 18. —. 2007. Evolution of the watering pot (Bivalvia, Pandoracea). Journal of shells (Bivalvia: Anomalodesmata: Molluscan Studies. 42:395-408. Clavagellidae and Penicillidae). Records of the Western Australian Museum. 24:19-64.