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Phoronis Pallida Family: Phoronidae

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Phoronis Pallida Family: Phoronidae Phylum: Phoronida Phoronis pallida Family: Phoronidae A lophophorate coelomate (Schneider, 1862; Silen, 1952) Description Bulb—(ampulla)-enlarged posterior end (fig. Size—one of the smaller phoronids: 15-30 1). mm long (Silen 1954): sp. pallida. Sand Internal Structure—much systematic work covered tube just a little larger (Silen 1952); based on longitudinal muscle patterns, etc., expanded animal can be 25% longer than not easily studied by casual field worker. P. tube. pallida muscles have unusual longitudinal and Color—trunk pale, white, posterior end light circular patterns, and few bundles of muscles red. Internal organs visible as red (contain (18-19). Giant nerve fibers found in this hemoglobin (Zimmer and Haderlie 1980). phylum - except in P. ovalis - also vary in Tentacles white, without pigmented size and number. P. pallida has one giant amoebocytes: sp. pallida (Silen 1954). Larva nerve fiber, on the left side - usual position in opaque yellow, tube yellow to brown-red phylum (Emig 1974). Nephridial structure is (from secreted matter) (Silen 1954). also important in systematics. Trunk—wormlike: un-segmented, smooth and Tube—separate, vertical, chitinous, covered soft, but faintly annulated (Hyman 1959), no with thin layer of sand grains. Membranous setae - all characteristic of phylum Phoronida. distally (Zimmer 2007). Distinctly flexed 1/3 of Can be faintly differentiated into several way to base: sp. pallida (Silen 1954) (fig. 6). zones: sp. pallida (Silen 1954). Trunk and Tube flexible, tough, can't be easily broken. whole tube curved toward anal side (Silen Basal end of tube open. 1954) (fig. 6). Larva—actinotroch (from which this species Lophophore—a horseshoe-shaped was first described (Schneider 1862)) is small: extension of the mesosome (Hyman 1959); 0.6 mm long, active; found on water's surface. includes mouth and consists of a crown of Mature larva found on substrate, has 5 pairs tentacles. Number of lophophore spirals, of tentacles (Silen 1954) (fig. 5). Young number of tentacles characteristic of sp. actinotrochs are photopositive and pallida - a single row of 50-140 tentacles, in a planktotrophic (Silen 1954). simple spiral (Emig 1974)(fig. 3). Tentacles—straight, finger-shaped: Possible Misidentifications Phoronida (Zimmer and Haderlie 1980); not Phoronids are worm-like, with an threadlike (fig. 2a). In P. pallida there can be unsegmented, though slightly annulated trunk 50-140, but usually around 50 (Zimmer and and a crown of tentacles on the anterior end. Haderlie 1980), sometimes more (S.F. Bay Some polychaetes also have this general specimens). Tentacles can be regenerated form. Phoronids, however, have no setae or (MacGinitie and MacGinitie 1949). segmentation on their trunks. Phoronid Anus—dorsal to mouth (Hyman 1959); tentacles are straight and finger-like, not digestive tract U-shaped (fig. 2). branched or thread-like, as in polychaetes. Nephridiopores—lateral to anus (fig. 2): The phoronid lophophore is circular-crescent excretory and for emission of sex cells shaped or a double spiral. (Hyman 1959). Only 2 genera of Phoronida and probably Collar—not present at base of lophophore: fewer than 20 species are known worldwide. genus Phoronis (Zimmer 2007) (figs. 1, 2, 3). Many of these can be found on the Pacific Lophophore base and trunk demarcation a coast, but only 3 are common intertidally: slight groove; collar, (if present, as in genus Phoronopsis harmeri, Phoronis Phoronopsis), extends all around trunk. (Do vancouverensis, and P. pallida. The main not confuse anus and nephridiopores on population of each of these species is likely dorsal base of lophophore with a true collar.) subtidal (Zimmer 2007). Phoronopsis spp. can be distinguished from Phoronis spp. by the presence in the Digitized 2012 – Last Updated 2014 by Kirstin Meyer– E-mail corrections to [email protected] former of a collar at the base of the P. hippocrepia (Wright), the European lophophore, lacking in Phoronis spp. The species, is considered to be separate from P. three Pacific representatives of this genus vancouverensis above (Emig 1971). include: Phoronopsis harmeri Pixell, 1912 (senior Ecological Information synonym of P. viridis (Hilton, 1930), a large Range—Scandinavia; Pacific coast of North common phoronid often found in great America. masses on the mudflats. Individuals can Local Distribution—Coos Bay: Charleston be green or white and up to 200 mm long, mudflats. with up to 300 green tentacles with white Habitat—in soft sand, muddy sand (Emig spots (Hyman 1959, Zimmer 2007). P. 1974); on intertidal mudflats. Commensal in harmeri is usually larger than P. pallida (up to Upogebia pugettensis burrows (Zimmer 2007) 60 mm long), and has a collar, as in all Salinity—all phoronids are marine (Zimmer Phoronopsis spp. It is also found in the and Haderlie 1980). Only one species, P. Atlantic (Azores). This species is abundant on euxinicola, is found in brackish water, in the Oregon and Washington tidal flats, and is Black Sea (Hyman 1959). These specimens largely distinguished from P. pallida by its collected at 30 ‰ (Coos Bay). size, color and its collar. Temperature—phoronids are found in P. pacifica (Torrey, 1901), found first in shallow waters of tropical and temperate Humboldt Bay, and described from Puget ranges (Hyman 1959); most are temperate Sound as well, is also considered a synonym (Zimmer 1980). Some can regenerate after of P. harmeri (Emig 1974). extremes of weather have left only fragments The third Phoronopsis species, P. in tubes: in winter (Italy) and summer (Japan) californica Hilton, 1930, is probably limited to (Hyman 1959). southern California. It has a large bright Tidal Level—intertidal, also subtidal at a orange lophophore with elaborate spirals; it is number of locations worldwide (Zimmer 2007) solitary, and can be up to 12" (300 mm) long down to 12m deep (Emig 1974). (Other (MacGinitie and MacGinitie 1949). phoronids can be found down to 140m.) There are four other species of Phoronis Associates—commensal in burrows of reported from our coast: Upogebia pugettensis, though not often found P. architecta Andrews, 1890 is an Atlantic with the sympatric mud shrimp Neotrypaea species, also found subtidally from southern californiensis (Zimmer 2007). California to British Columbia, and occasionally intertidally (Zimmer and Haderlie Quantitative Information 1980). Its lophophore is flesh-colored, or Weight— rarely reddish, with white bands and flecks. It Abundance— has no collar, (like P. pallida), but is 2x the size of the latter; its sand encrusted tube is Life History Information straight, not flexed. Reproduction—a simultaneous P. psammophila has been synonymized hermaphrodite: eggs and sperm extruded into with P. architecta (Emig 1982).P. ovalis body cavity from reproductive organs, fertile Wright, 1856 is much smaller even than P. eggs expelled into seawater via pallida, (only 6 mm long). It bores in shell and nephridiopores (MacGinitie and MacGinitie limestone and is not found 1949). In some species, larvae live among living freely in the mud. tentacles of adult female, but not in P. pallida, P. vancouverensis Pixell, 1912 (now which lacks nidamental (nesting) organs senior synonym of P. ijimai Oka, 1897) is (Emig 1974). No asexual propagation, whitish, like P. pallida. It is larger, however, although regeneration of crown of tentacles 20-50 mm long, and has 72-100 tentacles possible (Silen 1952). Eggs laid on 2 - 3 (average 90 according to Pixell ,1912), and successive summer nights (Sweden), 28 at a grows in intertwined clusters of great density, time (Silen 1954). often on pilings and on rocks. Its tubes are Growth Rate—fertilized egg immobile for 20 covered with detritus, not sand grains. hours; to blastula stage in 20 hours more. After gastrulation begins, hood develops; in 25-30 more hours, a ciliated ridge appears, Digitized 2012 – Last Updated 2014 by Kirstin Meyer– E-mail corrections to [email protected] becoming the crown of tentacles. First 5. MACGINITIE, G. E., and N. tentacles show after two days. (Growth MACGINITIE. 1949. Natural history of stopped in lab after six days (Silen 1954). The marine animals. McGraw-Hill Book actinotroch progresses from four tentacles to Co., New York. metamorphosis in 12-14 days. It is active and 6. PIXELL, H. L. M. 1912. Two new moves quickly horizontally and vertically - species of the Phoronidea from dives, floats, and rushes. Details of larval Vancouver Island. Quarterly Journal of development and phylogenetic implications Microscopical Science. 58:257-284. are given by Santagata (2004a) and a key to 7. SANTAGATA, S. 2002. Structure and larval stages is available in Shanks (2001). metamorphic remodeling of the larval Mature larvae are photonegative; pre- nervous system and musculature of settlement behavior is induced by a Phoronis pallida (Phoronida). waterborne cue from Upogebia pugettensis, a Evolution & Development. 4(1): 28-42. shrimp species with which P. pallida is 8. --------------- 2004a. Larval commensal (Santagata 2004b). development of Phoronis pallida Metamorphosis is triggered by (Phoronida): Implications for presence of proper substrate (mud, sand), morphological convergence and and takes 15 minutes. The actinotroch takes divergence among larval body plans. a horizontal position, ventral side down, then Journal of Morphology. 259: 347-358. evaginates metasomal sac. The transition is 9. ----------- 2004b. A waterborne cue for made from control by the larval the actinotroch larva of Phoronis neuromuscular system to that of the juvenile,
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