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Phoronis Pallida Class Phylum: Phoronida Class: Phoronis pallida Order: A lophophorate coelomate Family: Phoronidae Description 1959). Size: one of the smaller phoronids: 15-30 Collar: not present at base of lophophore: ge- mm long (Silen 1954): sp. pallida. Sand cov- nus Phoronis (Zimmer 2007) (figs. 1, 2, 3). ered tube just a little larger (Silen 1952); ex- Lophophore base and trunk demarcation a panded animal can be 25% longer than slight groove; collar, (if present, as in genus tube. Phoronopsis), extends all around trunk. (Do Color: trunk pale, white, posterior end light not confuse anus and nephridiopores on dor- red. Internal organs visible as red (contain sal base of lophophore with a true collar.) hemoglobin (Zimmer and Haderlie 1980). Bulb: (ampulla)-enlarged posterior end (fig. Tentacles white, without pigmented amoebo- 1). cytes: sp. pallida (Silen 1954). Larva opaque Internal Structure: much systematic work yellow, tube yellow to brown-red (from se- based on longitudinal muscle patterns, etc., creted matter) (Silen 1954). not easily studied by casual field worker. P. Trunk: wormlike: unsegmented, smooth and pallida muscles have unusual longitudinal and soft, but faintly annulated (Hyman 1959), no circular patterns, and few bundles of muscles setae - all characteristic of phylum Phoroni- (18-19). Giant nerve fibers found in this phy- da. Can be faintly differentiated into several lum - except in P. ovalis - also vary in size zones: sp. pallida (Silen 1954). Trunk and and number. P. pallida has one giant nerve whole tube curved toward anal side (Silen fiber, on the left side - usual position in phy- 1954) (fig. 6). lum (Emig 1974). Nephridial structure is also Lophophore: a horseshoe-shaped exten- important in systematics. sion of the mesosome (Hyman 1959); in- Tube: separate, vertical, chitinous, covered cludes mouth and consists of a crown of ten- with thin layer of sand grains. Membranous tacles. Number of lophophore spirals, num- distally (Zimmer 2007). Distinctly flexed 1/3 of ber of tentacles characteristic of sp. pallida - way to base: sp. pallida (Silen 1954) (fig. 6). a single row of 50-140 tentacles, in a simple Tube flexible, tough, can't be easily broken. spiral (Emig 1974)(fig. 3). Basal end of tube open. Tentacles: straight, finger-shaped: Phoroni- Larva: actinotroch (from which this species da (Zimmer and Haderlie 1980); not thread- was first described (Schneider 1862)) is small: like (fig. 2a). In P. pallida there can be 50- 0.6 mm long, active; found on water's surface. 140, but usually around 50 (Zimmer and Mature larva found on substrate, has 5 pairs Haderlie 1980), sometimes more (S.F. Bay of tentacles (Silen 1954) (fig. 5). Young ac- specimens). Tentacles can be regenerated tinotrochs are photopositive and (MacGinitie and MacGinitie 1949). planktotrophic (Silen 1954). Anus: dorsal to mouth (Hyman 1959); di- Possible Misidentifications gestive tract U-shaped (fig. 2). Phoronids are worm-like, with an un- Nephridiopores: lateral to anus (fig. 2): ex- segmented, though slightly annulated trunk cretory and for emission of sex cells (Hyman and a crown of tentacles on the anterior end. 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] Meyer, K. 2015. Phoronis pallida. 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. Some polychaetes also have this general There are 4 other species of Phoronis form. Phoronids, however, have no setae or reported from our coast: segmentation on their trunks. Phoronid ten- P. architecta Andrews, 1890 is an At- tacles are straight and finger-like, not lantic species, also found subtidally from branched or thread-like, as in polychaetes. southern California to British Columbia, and The phoronid lophophore is circular - cres- occasionally intertidally (Zimmer and Hader- cent shaped or a double spiral. lie 1980). Its lophophore is flesh-colored, or Only 2 genera of Phoronida and rarely reddish, with white bands and flecks. It probably fewer than 20 species are known has no collar, (like P. pallida), but is 2x the worldwide. Many of these can be found on size of the latter; its sand encrusted tube is the Pacific coast, but only 3 are common straight, not flexed. P. psammophila has intertidally: Phoronopsis harmeri, Phoronis been synonymized with P. architecta (Emig vancouverensis, and P. pallida. The main 1982).P. ovalis Wright, 1856 is much smaller population of each of these species is likely even than P. pallida, (only 6 mm long). It subtidal (Zimmer 2007). bores in shell and limestone and is not found Phoronopsis spp. can be distin- living freely in the mud. guished from Phoronis spp. by the pres- P. vancouverensis Pixell, 1912 (now ence in the former of a collar at the base of senior synonym of P. ijimai Oka, 1897) is the lophophore, lacking in Phoronis spp. whitish, like P. pallida. It is larger, however, The 3 Pacific representatives of this genus 20-50 mm long, and has 72-100 tentacles include: (average 90 (Pixell 1912)), and grows in in- Phoronopsis harmeri Pixell, 1912 tertwined clusters of great density, often on (senior synonym of P. viridis Hilton, 1930), pilings and on rocks. Its tubes are covered a large common phoronid often found in with detritus, not sand grains. great masses on the mudflats. Individuals P. hippocrepia (Wright), the European can be green or white and up to 200 mm species, is considered to be separate from P. long, with up to 300 green tentacles with vancouverensis above (Emig 1971). white spots (Hyman 1959, Zimmer 2007). Ecological Information P. harmeri is usually larger than P. pallida Range: Scandinavia; Pacific coast of North (up to 60 mm long), and has a collar, as in America. all Phoronopsis spp. It is also found in the Local Distribution: Coos Bay: Charleston Atlantic (Azores). This species is abundant mudflats. on Oregon and Washington tidal flats, and Habitat: in soft sand, muddy sand (Emig is largely distinguished from P. pallida by its 1974); on intertidal mudflats. Commensal in size, color and its collar. Upogebia pugettensis burrows (Zimmer 2007) P. pacifica (Torrey, 1901), found first Salinity: all phoronids are marine (Zimmer in Humboldt Bay, and described from Puget and Haderlie 1980). Only one species, P. eux- Sound as well, is also considered a syno- inicola, is found in brackish water, in the Black nym of P. harmeri (Emig 1974). Sea (Hyman 1959). These specimens collect- The 3rd Phoronopsis species, P. cali- ed at 30 ‰ (Coos Bay). fornica Hilton, 1930, is probably limited to Temperature: phoronids are found in shallow southern California. It has a large bright or- waters of tropical and temperate ranges ange lophophore with elaborate spirals; it is (Hyman 1959); most are temperate (Zimmer solitary, and can be up to 12" (300 mm) 1980). Some can regenerate after extremes long (MacGinitie and MacGinitie 1949). 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] of weather have left only fragments in tubes: havior is induced by a waterborne cue from in winter (Italy) and summer (Japan) (Hyman Upogebia pugettensis, a shrimp species with 1959). which P. pallida is commensal (Santagata Tidal Level: intertidal, also subtidal at a 2004b). Metamorphosis is triggered by pres- number of locations worldwide(Zimmer ence of proper substrate (mud, sand), and 2007) down to 12m deep (Emig 1974). takes 15 minutes. The actinotroch takes a (Other phoronids can be found down to horizontal position, ventral side down, then 140m.) evaginates metasomal sac. The transition is Associates: commensal in burrows of made from control by the larval neuromuscu- Upogebia pugettensis, though not often lar system to that of the juvenile, resulting in found with the sympatric mud shrimp Ne- the apoptosis of larval structures. This suc- otrypaea californiensis (Zimmer 2007). cession of events suggests lophotrochozoan Abundance: affinities (Santagata 2002). Finally, a thin tube is formed, and the worm begins to burrow. Life-History Information Food: all phoronids are ciliary mucus feeders, Reproduction: a simultaneous hermaphro- gathering suspended particles by tentacular dite: eggs and sperm extruded into body currents (Hyman 1959). Actinotrochs eat cavity from reproductive organs, fertile eggs peridinians, not diatoms (Silen 1952). expelled into seawater via nephridiopores Predators: (MacGinitie and MacGinitie 1949). In some Behavior: movement limited to emergence species, larvae live among tentacles of adult from anterior end of tube, and expansion of female, but not in P. pallida, which lacks crown (in undisturbed conditions), and to with- nidamental (nesting) organs (Emig 1974). drawal into tube if disturbed (Hyman 1959). No asexual propagation, although regenera- Adults not light sensitive (Hyman 1959). tion of crown of tentacles possible (Silen 1952). Eggs laid on 2 - 3 successive sum- Bibliography mer nights (Sweden), 28 at a time (Silen 1. EMIG, C. C. 1971. Remarques sur la 1954). systmatique des Phoronidea. Marine Biol- Larva: ogy . 8:154-159. Juvenile: 2. ——. 1974. The systematics and evolution Longevity: of the phylum Phoronida. Journal of Zoo- Growth Rate: fertilized egg immobile for 20 logical Systematics and Evolutionary Re- hours; to blastula stage in 20 hours more. search. 12:128-151. After gastrulation begins, hood develops; in 3. EMIG, C.C. 1982. The biology of Phoroni- 25-30 more hours, a ciliated ridge appears, da. Advances in Marine Biology. 19: 1-89. which becomes the crown of tentacles. First 4. HYMAN, L. H. 1959. The Invertebrates: tentacles show after 2 days.
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