Phylum: Annelida Owenia collaris Class: Polychaeta, Sedentaria, Canalipalpata Order: Sabellida A tube-dwelling polychaete worm Family: Oweniidae Taxonomy: O. collaris was originally con- posterior segments short (Fig. 1). Thorax and sidered a subspecies of O. fusiformis abdomen not morphologically distinct. 18-28 (Hartman in 1955) and was later defined as segments (Dales 1967). a valid species by the same author v(1969) Anterior: Prostomium reduced with no based on the presence of a thoracic collar. sensory appendages except frilly buccal Based on morphological characters, Dauvin membrane or tentacular crown. Prosto- and Thiébaut (1994) designated O. fusiform- mium fused with peristomium, forming a collar is as a cosmopolitan species, considering whose margin is complete except for a pair of most Owenia species (including O. collaris) ventral lateral notches (Hartman 1969) (Fig. junior synonyms of O. fusiformis while re- 2b). Mouth is terminal (Blake 2000) and sur- ducing the genus Owenia to two species. rounded by three peristomial lips (one dorsal, Character-based and molecular phylogenet- two ventral) (Fig. 4), which can be used di- ics have revealed that O. fusiformis is a rectly for feeding (Dales 1967). cryptic species complex (Blake 2000; Ford Trunk: Body segments are inconspicu- and Hutchings 2005; Capa et al. 2012) in ous and only marked by presence of setae. which O. collaris is a distinct species (Blake Abdominal groove present and dorsal glandu- 2000). lar ridges absent (Blake 2000). Posterior: Pygidium lobed (10 or more Description lobes) when expanded, but is usually con- Size: Individuals are moderate sized and up tracted when collected (Berkeley and Berke- to 54 mm (Blake 2000) in length and 3 mm ley 1952; Blake 2000) (Fig. 1). in width. Although specimens up to 100 mm Parapodia: Reduced and biramous both no- in length (Berkeley and Berkeley 1952) and tosetae and neurosetae beginning on setiger tubes up to 90 mm in length (Hartman 1969) four and continuing to posterior. “Neuropodia have been reported. The specimen upon from setiger four form nearly encircling girdles which the description is based was 27 mm in of closely packed uncini at anterior end of length and 1.0 mm in width with 18 segment'' (Hartman 1969) (Figs. 2b, 3b). segments (from Coos Bay). Each uncinus has a straight stem and 2 teeth Color: Buccal membrane (crown) is pale (Fig. 3c). gray green, with white band. Body pale Setae (chaetae): Notosetae consist of serrat- green flushed with pale reds. Preserved ed capillaries (Blake 2000). First three tho- specimens are pale with large reddish brown racic setigers have capillary notosetae only shield pattern running length of first three (Fig. 2a) (genus Owenia). Setiger three is setigers (Fig. 2a). more dorsal and has shorter notosetae (Blake General Morphology: Slender and fragile 2000). Abdominal notosetae are thin. but somewhat rigid with truncated anterior Neurosetae are composed of dense small that tapers posteriorly. (Blake 2000). hooks with long shafts (Blake 2000). Body: Body cylindrical with first four anterior Eyes/Eyespots: There is confusion about the segments short, middle segments long and 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. 2014. Owenia collaris. 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. presence or absence of peristomial eyes in cause it is not feathery, or composed of long this species. Two ventral eyes were report- branchiae, tentacles or of palps. It encircles ed (sp. collaris, Hobson and Banse 1981) the entire anterior end of the worm. and observed (Fig. 2b). However, Hartman Other tube-dwelling polychaete fami- (1969), Blake (2000) and Blake and Ruff lies have buccal tentacles, a crown of radi- (2007) indicate eyespots are absent. oles or palps, but none has the entire anteri- Anterior Appendages: A buccal membrane or end transformed into a tentacular mem- at worm anterior forms a crown-like funnel brane and thus a greatly reduced prostomi- (genus Owenia). The crown has 4–10 main um. In addition, oweniids have very short branches (eight, Blake 2000) divided into posterior segments with middle and anterior 100’s of slender tips all of same length segments long. Other tube-dwelling poly- (Hartman 1969) (Fig. 2). The membrane chaete families referenced in this guide in- functions in respiration and feeding (Dales clude: Ampharetidae (see Hobsonia florida), 1967). Sabellidae (see Eudistylia vancouveri), Branchiae: Terebellidae (see Pista pacifica and Burrow/Tube: Cylindrical or spindle-shaped Thelepus crispus). tube, up to 90 mm long, of overlapping shell There are 4 other genera in the fami- fragments and/or sand grains. Each grain is ly Oweniidae: attached at its one end, giving tube a tiled Galathowenia spp. have a prostomi- appearance (Fig. 1a). Tube lining is close- um with a midventral cleft surrounded by fitting, chitinous and tough (genus Owenia) overlapping ventral membranes but lacks and composed of fine filaments secreted by anterior appendages. The type species, G. seven pairs of thread glands. Tube grains, africana was described from South Africa usually light-colored, are cemented together (Dales 1967; Blake 2000), but three un- by the buccal organ (Watson 1901), described species are reported offshore of concealed by the crown. Tubes taper at California (Blake and Ruff 2007). both ends. Myriowenia spp. are recognizable by Pharynx: Bears a proboscis with muscular having deeply bilobed prostomiuma, with pad (Fauchald 1977) and pharynx is not paired palps and no tentacular crown. Their eversible (Blake 2000). tubes are loose-fitting and easily torn. M. Genitalia: californiensis is reported from offshore Nephridia: central California to Oregon in mixed sediments (Blake and Ruff 2007). Possible Misidentifications Myriochele spp. have a rounded Oweniida are all tube dwellers. The prostomium, no tentacular crown and no Oweniidae is a small family with its own midventral cleft. Like Owenia, they have order (Fauchald 1977). It is characterized only notosetae in the first two or three by its lobed or membranous prostomium setigers. Of the dozen or so species of fused to the anterior segments. All the an- Myriochele worldwide (Hobson and Banse terior segments are long (except the first 1981), three species are reported offshore four in this species) and the posterior seg- in California. Myriochele striolata is the only ments are short. The neuropodial hooks species known in nearshore sediments occur in dense horizontal bands and no- (Blake and Ruff 2007). This species is tosetae are capillary. The prominent buc- distinct in its small size (7–8 mm in length, cal membrane of Oweniidae is unique be- <1 mm in width and 16–17 setigers) (Blake 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] 2000). Reproduction: The reproduction and larval Myrioglobula sp. also have a round- development have been described by Smart ed prostomium and no crown of tentacles, and von Dassow (2009). Dioecious and itero- however the first setiger has only notose- parous, gametes are loose in the coelom tae, but no species in this genus are cur- (Smart and von Dassow 2009) in males and rently reported locally (Blake and Ruff females which spawn March through Septem- 2007) ber (Washington and Oregon) (Smart et al. The genus Owenia, is characterized 2012). Colorless eggs (70–80 µm) and sperm by its tentacular crown, its lack of (4 µm) are released through paired pores in neurosetae on the first three setigers, and the worm posterior. Once fertilized, cleavage its close-fitting, firm tube (Fauchald 1977). is spiral, gastrulation occurs at 8–9 hours, em- Owenia fusiformis differs from O. bryos are ciliated and swimming at 24 hr and collaris as the latter species has a collar develop through trochophores to mitraria lar- (=collaris), anteriorly (Hartman 1969). Ow- vae (12˚ C, Smart and von Dassow 2009). enia johnsoni has much less anterior pig- Larva: Planktotrophic mitraria larvae are ment than O. collaris. Additionally, the ten- characterized by triangular bodies with undu- tacular crown of O. collaris is shorter and lating ciliated margins (Crumrine 2001; Pernet bears fewer main branches than O. john- et al. 2002), have two red eyes and are recog- soni. The posterior end is grooved in O. nizable by two extremely long bundles of collaris, unlike O. johnsoni (Blake 2000). chaete, which develop from individual chaetal sacs. These chaetae extend when the larva Ecological Information is disturbed (Fernald et al. 1987). A juvenile Range: Type locality is Santa Catalina Is- rudiment develops after four weeks (12˚ C). land (Hartman 1969). Cosmopolitan distri- At metamorphosis, the larval body is resorbed butions previously reported (Berkeley and into the collar of the juvenile worm (Smart and Berkeley 1952) are likely that of O. fusiform- von Dassow 2009). is. Blake (2000) suggests that O. collaris is Juvenile: Post-metamorphosis juvenile O. found offshore in southern and central CA collaris are approximately 800 µm in length and this species is also reported in OR and have a prostomium and peristomium. The (Blake and Ruff 2007). juvenile has 7–8 segments bearing 1–2 sets Local Distribution: In Coos Bay including of chaetae, a pygidium and begins assem- South Slough and bay mouth. Also Yaquina bling a tube rapidly. They grow anterior tenta- Bay. cles and reach 1300 µm in length after 24 Habitat: Forms large, dense colonies in mud days (Smart and von Dassow 2009).