Phascolosoma Agassizi Class: Phascolosomatidea
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Phylum: Sipuncula Phascolosoma agassizi Class: Phascolosomatidea Order: Phascolosomatida Pacific peanut worm Family: Phascolosomatidae Taxonomy: The evolutionary origins of 3) (Rice 2007). Body wall divided into longitu- sipunculans, recently considered a distinct dinal bands that can be noticeable on outside phylum (Rice 2007), is controversial. Cur- (Fig. 4). No true segmentation. rent molecular phylogenetic evidence (e.g., Introvert: The introvert resembles a neck and Staton 2003; Struck et al. 2007; Dordel et al. is slender and can be extended to be longer 2010; Kristof et al. 2011) suggests that than trunk (Fig. 1) (Stephen 1964). It is Sipuncula be placed within the phylum composed of an anterior oral disc, which Annelida, which is characterized by Oral Disc: The oral disc is bordered by segmentation. Placement of the a ridge (cephalic collar) of tentacles enclosing unsegmented Sipuncula and Echiura within a dorsal nuchal gland. Inconspicuous, finger- Annelida, suggests that segmentation was like and not branched (Rice 1975b), the 18– secondarily lost in these groups (Struck et 24 tentacles exist in a crescent-shaped arc, al. 2007; Dordel et al. 2010). enclosing a heart-shaped nuchal gland (Fig. 2). Description Mouth: Inconspicuous and posterior to Size: Up to 15 cm (extended) and common- oral disc, with thin flange (cervical collar) just ly 5–7 cm in length (Rice 1975b). The illus- ventral to and outside the arc of tentacles trations are from a specimen (Coos Bay) 13 (Fig. 2). cm in length. Young individuals are 10–13 Eyes: A pair of ocelli at anterior end mm in length (extended, Fisher 1950). Ju- are internal and in an ocular tube (Fig. 4) veniles can be up to 30 mm long (Gibbs (Hermans and Eakin 1969). 1985). The illustrated specimen weighed Hooks: Tiny chitinous spines on the approximately 5.3 g (wet weight). introvert anterior are arranged in a variable Color: Dark pigment blotches, dark conical number of dark, colored rings (usually 15–24 papillae, particularly at posterior end but al- in this species) (Fig. 2). The first three rows so along introvert (Plate 120, Rice 2007). can be small and colorless, while the last two The trunk was brown in the illustrated speci- can be incomplete (due to wear) (Fisher men and the skin was thick and rough, the 1950). introvert was pale, shiny, smooth, and with Trunk: The trunk is bulbous, posteriorly point- dark bands and splotches. The tentacles ed and can be divided into longitudinal bands were light tan (Fig. 1). (not always obvious exteriorly). When con- Papillae: Papillae are conical glandular tracted, the trunk is peanut-shaped (Fig. 3). structures, each with hard round center on a Anus: Dorsal, and at anterior-most platelet (Fig. 1a). Papillae are thickest trunk (Rice 2007), the anus is recognizable as around the posterior end and mid dorsally, a light, raised area (Fig. 1). Intestinal tract is near the anus. U-shaped (Fig.4). Body: Body divided into anterior introvert Nephridiopore: Lateral and just poste- and posterior trunk regions and the introvert rior to anus (Fig. 1). Nephridia are two long can be retracted entirely into the trunk (Fig. 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. and M. Jarvis. 2015. Phascolosoma agassizi. 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 Biol- ogy, Charleston, OR. structures lying freely within the coelom (Fig. of these are likely to be found in the Coos Bay 4). area. Phascolosoma agassizii is readily rec- Gonads: Occur at origin of ventral ognizable by its long, pale introvert with dark retractors (Fig. 4). Sexual products bands and rows of hooks, its single crescent (gametes) extruded through nephridiopores of 15–24 finger-like tentacles with the mouth (Fig. 1). outside the arc, and by its conical papillae on a rough brown trunk. Possible Misidentifications The Sipunculidae also have well de- Sipunculans are fairly easily distin- fined longitudinal muscle bands in the body guished from other worms by their lack of wall, but their oral tentacles completely sur- segmentation and by their peanut-like shape round the mouth (Stephen and Edmonds when contracted, hence, their common 1972; Rice 2007). Two species occur locally name: peanut worms. The echiurans, or (Siphonosoma ingens and Sipunculus nudus) spoon worms, are a similar group that are and both have a short introvert, numerous also unsegmented and of a similar size, tentacles and tend to be larger than P. agas- shape and habitat. They have an extensible sizii at 12–50 cm (P. agassizii is usually 5–7 spoon-shaped proboscis, however, and a cm) (Rice 2007). posterior anus (not mid-body, as in Sipuncu- Golfingiidae is another sipunculan fam- la). Priapula is a small phylum of sausage- ily, characterized by continuous muscle tissue shaped non-segmented worms. Priapulids in the body wall (not bands). The tentacles are predatory worms with a bulbous spiny surround the mouth (unlike the crescent proboscis, quite unlike any in Sipuncula. shaped arc of tentacles in Phascoloso- Local representatives in the Sipuncula are matidae). The locally occurring genus is Golf- divided into four families: Sipunculidae, Golf- ingia. Golfingia (margaritacea) margaritacea, ingiidae, Themistidae and the Phascoloso- a small and threadlike species that is only 25 matidae. mm long. It is known (so far) only from Mon- Phascolosoma agassizii and its family terey, California (Rice 1975b). Golfingia pu- (Phascolosomatidae) are characterized by a gettensis (from Puget Sound) (Fisher 1952) is horseshoe shaped arc of tentacles lying dor- whitish to dark grey, smooth, with only incon- sal to the mouth by the four retractor mus- spicuous papillae. Its introvert is about half cles (Fig. 4) and by the longitudinal muscle the body length, and is without hooks (Hyman bands in the body wall (except for the spe- 1959). cies Apionsoma misakianum, formerly Golf- Members of the Themistidae are char- ingia hespera). There are 60 species in the acterized by tentacles that are long, extending Phascolosoma genus and nearly all are dis- and branching (rather than filiform). Three tinguished by rings of single hooks on the species in the genus Themiste (formerly Den- introvert (Stephen and Edmonds 1972). On- drostomum) occur locally including T. dyscri- ly P. agassizii occurs locally. Phascolosoma ta, T. hennahi and T. pyroides. Themiste py- japonicum, a Japanese species, has been roides has black or brown spines on the intro- reported from Vancouver Island. Its trunk vert and tentacles that form four main stems. papillae have much larger platelets than Themiste dyscrita resembles T. pyroides, but those of P. agassizii (Fisher 1950). Phasco- the collar at the tentacle base is reddish pur- losoma perlucens, P. rickettsi (=pectinatum), ple in color. Themiste hennahi is similar to and P. puntarenae are eastern Pacific spe- both species but has a cylindrical body and cies found from California southward. None lacks collar pigment. 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] Ecological Information 1950). Adults from Vostok Bay kept together Range: Type locality is Mendocino, Califor- in lab at 20–22ºC spawned after several nia (Schulze et al. 2012). Known range in- hours (Adrianov et al. 2011). Frequently, cludes Kodiak Island, Alaska, to Bay of San nephridiopores in males and females will be Quintin, Baja California. Also found in west- visibly swollen when ready to spawn and may ern Pacific (Adrianov et al. 2001), although spawn following collection or water changes. see Schulze et al. (2012) for evidence that Spawning typically occurs at night in the lab this large geographic range may include (Rice 1987). many separate and cryptic species. Embryological development is holo- Local Distribution: Coos Bay distribution blastic, spiral, unequal cleavage (Sipuncula). includes Fossil Point, Clam Island and also There is data on development from the on the outer coast, in the rocky intertidal at eastern and western Pacific, but the western Cape Arago. Pacific data may be from a different species. Habitat: Individuals nest or burrow in rock Development is faster and eggs are smaller in and gravelly mud (but without a permanent P. agassizii from the Sea of Japan than tube). Also found amongst shells, holdfasts, eastern Pacific populations (Adrianov et al. under rocks or in cracks with Phyllospadix 2011; Rice 1967). Eggs spherical to elliptical, roots and the hydrocoral, Allopora, in Mytilus 100–140 µm in diameter in Humboldt Bay, 70 beds and protected situations. Not found in –100 µm in diameter in Vostok Bay, and 140 shifting sediments (Fisher 1950). x 110 x 91 µm at their longest, widest, and Salinity: Collected at 30 in Coos Bay. thickest points in Washington (Rice 1987). Temperature: Temperate to warm waters. Mature eggs are orange-pink (Vostok Bay), Tidal Level: From mid intertidal down to 60 bright yellow or orange (Washington). Eggs m, but most common in the lower half of the bear a small amount of yolk and develop in intertidal zone and just below low tide the lab (18–20ºC in Adrianov et al. 2011) with (Fisher 1950). first cleavage, blastula, and gastrula at 2.5, Associates: Known associates include sev- 16, and 24 hrs respectively (12 °C, Rice eral polychaetes (Thelepus and Glycera), 1987). chitons, serpent stars, shore crabs, Larva: P. agassizi has two larval stages. gastropod, Nucella. First, an encapsulated, non-feeding Abundance: The most common sipunculan (lecithotrophic) trochophore at 2.5 days with a (California, Rice 1975b) from Alaska to Pt.