Sternaspis affinis Stimpson, 1864, emended

Sendall, Kelly & Salazar-Vallejo, Sergio I., 2013, Revision of Sternaspis Otto, 1821 (Polychaeta, Sternaspidae), ZooKeys 286, pp. 1-74 : 20-23

Sternaspis affinis Stimpson, 1864, emended Figures 1B25

Sternaspis affinis Stimpson, 1864: 159; von Marenzeller 1890: 5-8, Pl. 1, fig. 7.

Sternaspis fossor : Treadwell 1914: 215; Chamberlin 1919: 405-406; Moore 1923: 21; Berkeley 1930: 69; Berkeley and Berkeley 1941: 19 (list), 51; 1952: 59-60, fig. 123; Hartman 1963: 59, 1969: 351-352, fig. 1; Fauchald 1972: 238-239 (partim); Bilyard and Carey 1979: fig. 2, Tab. 2, 1980: 22; Fauchald and Hancock 1981: 35 (non Stimpson 1853).

Sternaspis fossor ?: Moore 1908: 358.

Sternaspis scutata : Hartman and Reish 1950: 38; Pettibone 1954: 309-310, fig. 35 a, b (partim); Fauchald 1077: 113, fig. 33C, D; Hobson and Banse 1981: 18, 19, 63, Tab. 3, fig. F (non Ranzani 1817).

Type material.

Canada, British Columbia, Strait of Georgia. Neotype (RBCM 005-138-001), and 15 paraneotypes (RBCM 005-138-002), 49°10'47"N, 123°18'02"W, 80 m, 13-III-2003.

Additional material. Canada, British Columbia. 2 spec. (LACM n2939), Departure Bay, mud and rocks, 18-VII-1940, G.E. & N. MacGinitie, coll. 1 spec. (NHMW 1565), Vancouver Island, 1875. 34 spec. (RBCM 987-254-023), Vancouver Island, southwest of Cape Beale, 48°35'54"N, 125°08'24"W, 104 m, 23-VII-1987. 17 spec. (RBCM 002-148-001), Vancouver Island, Trevor Channel, Helby Island, 48°50'00"N, 125°10'00"W, 19-VI-2002. 1 spec. (RBCM 996-148-004), Vancouver Island, Nanoose Bay, 49°15'30"N, 124°08'30"W, 28 m, 4-VI-1996. 3 spec. (RBCM 991-924-006), Vancouver Island, Saanich Inlet, 48°42'36"N, 123°31'00"W, 60-70 m, 16-II-1987. 24 spec. (RBCM 988-9-032), Dixon Entrance, west of Dundas Island, 54°29'40"N, 131°11'01"W, 143 m, 23-I-1988. Four spec. (RBCM 990-320-043), Vancouver Island, southwest of Nootka Sound, 49°25'14"N, 127°21'55"W, 1000-1166 m, 3-II-1990. U.S.A., Alaska. 2 spec. (CAS 151054), Boca de Quadra Inlet, III-1981. 12 spec. (CAS 17805), Gulf of Alaska, Cook Inlet, 59°34'54"N, 151°30'24"W, 99 m, 22-X-1976. 4 spec. (CAS 18987), Chukchi Sea, 67°15'N, 165°25'W, 33 m, 11-IX-1907. 2 spec. (USNM 63142), Gulf of Alaska, 59°51'30"N, 142°06'50"W, 53-100 m, 11-VII-1976. Washington. 4 spec. (RBCM 985-474-001), west of Cape Flattery, 48°25'24"N, 125°14'00"W, 168 m, 18-VI-1985. Oregon. 8 spec. (USNM 74917), mouth of Columbia River, 91 m, 15-IX-1961. California. 20 spec. (ANSP 3315), Monterey Bay, 66 m, 13-V-1904. Mexico, Gulf of California. 2 spec. (SIO A838), Isla Angel de Ia Guarda, 562-642 m, 18-I-1968. 16 spec. (SIO A839), Isla Angel de Ia Guarda, 1474 m, 18-I-1968.

Description.

Neotype (RBCM 005-138-001), with body cream to light tan, sometimes greyish (Fig. 5A, B). First six segments smooth with a few minute cuticular papillae widely and evenly spaced. Remaining segments more papillate and opaque in appearance. Segments seven and eight slightly more opaque and dense than preceding ones, with stout cuticular papillae especially near genital papillae, some cuticular papillae with small grains of sediment adhered to bases. Body 15.5 mm long, 5.0 mm wide (other specimens up to 22 mm long, 7 mm wide), about 29 segments.

Prostomium hemispherical, opalescent, translucent, sometimes with crescent shaped red eyespots laterally on smaller individuals (Fig. 5C, insert). Peristomium round, without papillae. Mouth oval, covered by papillae, extending from base of prostomium to anterior edge of second segment.

First three chaetigers with 8-14 light bronze, widely separated, slightly falcate introvert hooks per bundle, each with subdistal dark areas (Fig. 5C). Genital papillae protrude ventrolaterally from intersegmental groove between segments 7 and 8.

Pre-shield region with 7 segments, with papillae evenly spaced, slightly denser than on anterior segments, although less so ventrally, and in single rows of clusters of short filaments closer to ventro-caudal shield, especially on dorsal surface, rarely showing delicate short capillary chaetae protruding laterally from body wall.

Ventro-caudal shield with concentric lines, slightly ribbed; suture extended throughout shield (restricted to the anterior region in larger specimens). Anterior margins rounded; anterior depression deep; anterior keels not exposed (Figs 1B, 2, 5B, D). Lateral margins gently rounded (straighter in larger specimens), not expanding posteriorly. Fan truncate, almost straight in juveniles, sometimes with median notch, becoming crenulated in larger specimens.

Marginal chaetal fascicles include 10 lateral ones (Fig. 5E), chaetae ovally arranged, and five posterior fascicles, chaetae in a linear arrangement. Peg chaetae on conical extensions emerging under most prominent oblique rib of the shield. Peg chaetae with stout base in cross section; a small fascicle of delicate capillary chaetae (peg-associated capillary chaetae) between peg chaetae and first fascicle of posterior chaetae.

Branchiae numerous, thick, coiled, slender, long, protruding from two oval plates, separated by a wide angle, on either side of anus. Additional fine, long filamentous papillae extending to lateral and posterior margins of shield.

Neotype locality.

British Columbia, Canada, Strait of Georgia.

Remarks.

It appears that Sternaspis affinis has not been reported since 1875. However, many collections hold specimens collected over the last hundred years of what appears to be the only species present along the northeast Pacific coast of North America, from the Beaufort Sea to California, and into the Gulf of California. These have been labelled either as Sternaspis scutata or Sternaspis fossor .

The original description by Stimpson is brief and only includes a scant comparison of the cuticle with the Atlantic species, Sternaspis fossor . As Stimpson’s description agrees with the characters of the specimens found along the northeast Pacific coast, we propose the emendation above with the designation of a neotype.

The taxonomic status of Sternaspis affinis Stimpson, 1864 needs clarification because it has been regarded as a junior synonym of a Northwestern Atlantic species, Sternaspis fossor Stimpson, 1853, or of the Mediterranean species, Sternaspis scutata (Ranzani, 1817). The proposal of a neotype together with the above description and illustrations will clarify the current situation ( ICZN 1999, Art. 75.3.1-75.3.3). The original material was deposited in the Smithsonian and later transferred to Chicago when William Stimpson was appointed director of the local Academy of Sciences in 1866, but they were destroyed in 1871 during the great Chicago fire (http://www.si.edu/oahp/ScientificIllustrators/WStimpson.html; ICZN 1999, Art. 75.3.4). Despite the fact that the original description was brief, Sternaspis affinis seems to be the only species living in the type locality region, and we are confident that the neotype corresponds to the species ( ICZN 1999, Art. 75.3.5). The proposed neotype was collected in the type locality ( ICZN 1999, Art. 75.3.6), and it has been deposited in the Royal British Columbia Museum ( ICZN 1999, Art. 75.3.7).

Sternaspis affinis resembles Sternaspis fossor , Sternaspis maior and Sternaspis islandica as they all have shields with rounded anterior margins, lateral margins slightly rounded, and posterior margins reaching or slightly expanded beyond the posterolateral corners. However, Sternaspis islandica differs by having a very shallow anterior depression, whereas the two other species have deep anterior depressions. The remaining three species differ because in Sternaspis affinis and Sternaspis maior the radiating ribs and posterior corners are often distinct, whereas they are barely developed, or not at all in Sternaspis fossor . Therefore, Sternaspis affinis is very similar to Sternaspis maior but their main difference lies in the relative development of concentric lines which are distinct in Sternaspis affinis and not visible or barely visible in Sternaspis maior .

Distribution.

Alaska, USA (in the Gulf of Alaska) south along the coast and inland waters to Monterey, California, USA, and into the Gulf of California. This species, identified as Sternaspis fossor , has been regarded as one of the most abundant ones along the coast in the East Sound of the San Juan Islands ( Weese and Macnab 1930), and along the Washington coast in 95-154 m with sediment having 50-68% mud ( Lie and Kisker 1970). Moore (1923: 218) reported two species from Southern California, based upon the number of chaetal fascicles along the shield margins; one with 16 total bundles found in 441-492 m, and the other, smaller in size, with 15 total bundles and collected in sediments at 92-1190 m.