Phylum: Annelida Halosydna brevisetosa Class: Polychaeta, Errantia Order: Phyllodocida, Aphroditiformia Family: Polynoidae, Lepitonotinae Taxonomy: Eastern Pacific polynoids are Trunk: often reported with wide distributions result- Posterior: Posterior three segments ing in numerous synonymies. Although oth- with dorsal cirri. Pygidium bears one pair of er synonyms are reported, the most com- anal cirri and anus is dorsal and between seg- mon and recent for H. brevisetosa is H. ments 35–36 (Salazar-Silva 2013). johnsoni. These two species have Parapodia: Biramous. Notopodia smaller overlapping ranges centrally, but the range than neuropodia (Fig. 3). Neuropodia with of H. brevisetosa extends more northerly rounded lobe near tip of acicula. Dorsal cirri into colder waters while H. johnsoni is more expanded distally with filiform tip and ventral common in warmer, southern regions. The cirri are short, with fine tip (Salazar-Silva variation in setal morphology between them 2013). was once believed to be temperature- Setae (chaetae): All setae simple. Notosetae induced and they were synonymized short and serrate. Neorsetae falcate, with (Gaffney 1973). However, after analyzing rows of spines toward the tips, which are en- type material from both species, Salazar- tire. Neurosetae more abundant than notose- Silva (2013) determined that the two are tae (Fig. 3) (Salazar-Silva 2013). different species based on the morphology Eyes/Eyespots: Two pairs of eyes present at of neurosetae and re-described them. posterior prostomium (Fig. 2). Anterior Appendages: Three anterior anten- Description nae (Fig. 2) and two palps (Halosynda, Sala- Size: Average size range is 40 to 100 mm in zar-Silva 2013). length (Hartman 1968). The illustrated Branchiae: specimen was 22 mm in length. Most scale Burrow/Tube: worms are less than a few centimeters long, Pharynx: Proboscis strongly developed, with however, commensal specimens can be four jaws and nine pairs of papillae (Salazar- larger than free-living (Haderlie 1980; Ruff Silva 2013). 1993). Genitalia: Color: Variable body color. This specimen Nephridia: had mottled brown scales, with black and white spots. Polynoidae-specific character General Morphology: Short worms, dorso- Elytra: 18 pairs occurring on segments 2–33 ventrally flattened with scale-like plates (see (segments 2, 4, 5–27 on every odd segment, Elytra) dorsally (Polynoidae, Ruff 1993). and 28, 30, 31, 33) (Fig. 1). Elytra morpholo- Body: Thin body that is sub-rectangular with gy is reniform to ovate, varied in color, and 36 total segments (Salazar-Silva 2013). with a few tubercules. Body widest medially, tapering at both ante- Possible Misidentifications rior and posterior ends (Fig. 1). The number of pairs of elytra make Anterior: Prostomium bilobed and identification easy among polynoids. The 21 most broad at posterior (Fig. 2). currently accepted Halosydna species 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. 2015. Halosydna brevisetosa. 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. worldwide are characterized by possessing busta, Thelepus crispus, Eupolymnia hetero- 36 segments and 18 pairs of elytra (Hartman branchia) (McGinitie and McGinitie 1949; 1938). The genera most similar to Fernald et al. 1987). Prefers clean waters Halosydna are Harmothoe, Lepidathenia, and seldom occurs where dissolved oxygen and Arctonoe, but only Halosydna species levels drop below 2.5 mg/I (Haderlie 1980). have 18 pairs of elytra (Ruff 1993). For Commensal individuals are not chemically example, Harmothoe, a closely related attracted, but possibly exhibit a tactile res- genus, has only 15 pairs of elytra (Barnich ponse to the host (Davenport and Hickok and Feige 2009). 1950). Species differentiation is usually by Abundance: Most common scaleworm in elytra morphology (Salazar-Silva 2010; Sal- central, northern California (Blake and Ruff azar-Silva 2013). H. johnsoni, a southern 2007) and also very abundant in Oregon and California species, has been confused with Washington. H. brevisetosa in the past. The difference Life-History Information between these two species is that H. bre- Reproduction: Dioecious with external fertili- visetosa has elytra with fringed marginal pa- zation (Ruff 1993). Gonads in segments 12– pillae that are absent in H. johnsoni (mid- 34. In Tomales Bay, California, ripe adults body and posterior). Furthermore, the were observed in August and the larvae of H. neurosetae in H. brevisetosa are complete brevisetosa are most common in plankton rather than bidentate as in H. johnsoni samples in the late summer months (Blake (Salazar-Silva 2006; Salazar-Silva 2013). 1975). Other species of the genus Halosydna do Larva: Trochophore larvae were described not occur in the Northwest. from wild-caught individuals by Blake (1975) Ecological Information and are recognizable by a wide (400 µm) and Range: Type locality is Sausalito, San Fran- flattened episphere, anterior to the prototroch cisco, California. Known range includes (Crumrine 2001). They have two pairs of southern California to Alaska. eyes and a small apical tuft at the anterior Local Distribution: Very common at sites in end. A ciliated neurotroch, which extends South Slough (Hartman and Reish 1950). from the prototroch to the larval posterior, ori- Habitat: Free-living individuals are found on ginates near the mouth. Also near the mouth, or under rocks, pilings, and amongst mussel on the left side is a large tuft of long cilia. beds. H. brevisetosa also occur Early and late H. brevisetosa metatrochopho- commensally with a variety of invertebrates res lack a telotroch. Black pigment can be (see Associates). observed in random patches near the proto- Salinity: troch and episphere. Late metatrochophores, Temperature: 550 µm in length, have five pairs of elytra and Tidal Level: Intertidal. Individuals collected three pairs of eyes (Blake 1975). at a tidal elevation of 0.15 m above the Juvenile: Young juveniles are 900 µm in mean tide level in South Slough. length, with 11 setigerous segments, six pairs Associates: Commensal individuals occur of elytra, all anterior appendages, two pairs of with mud-dwelling species such as hermit eyes and anal cirri (Fig. 2, Blake 1975). crabs (Paguristes), moon snails (Polinices) Longevity: and other polychaetes (e.g., Pista pacifica, Growth Rate: observed in South Slough), Amphitrite ro- Food: Voracious eaters (cannibals in captiv- 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] ity) and individuals may share host food (eds.). Stanford University Press, Stan- when commensal. ford, CA. Predators: 9. HARTMAN, O. 1938. 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