Scoloplos californiensis, Blake, 2020

Blake, James A., 2020, New species and records of deep-water Orbiniidae (Annelida, Polychaeta) from the Eastern Pacific continental slope, abyssal Pacific Ocean, and the South China Sea, Zootaxa 4730 (1), pp. 1-61 : 29-31

Scoloplos californiensis new species

Figure 14

urn:lsid:zoobank.org:act:63650C44-3B94-4CD3-A541-E4A57F9B849F

Scoloplos armiger: Hilbig & Blake 2006: 265 . Not Müller 1776.

Material examined. Continental slope, off northern California, US EPA 102 Site Selection Survey, off Half

Moon Bay, R / V Point Sur, coll. J.A. Blake: north of Pioneer Canyon, Sta. 3-12, 15 Sep 1991, 37°25.03′N, 123°18.00′W, 1745 m, holotype ( LACM-AHF Poly 11664) ; Sta. 3-14, 15 Sep 1991, 37°23.51′N, 123°12.16′W, 1880 m, paratype ( LACM-AHF Poly 11665) ; south of Pioneer Canyon, Sta. 4-15, 19 Sep 1991, 37°12.42′N,

123°15.81′W, 1730 m, paratype ( LACM-AHF Poly 11666).

Description. An elongate, narrow-bodied species, cylindrical in cross section. Holotype complete, in three pieces, with about 120 setigers, 21.7 mm long, 0.51 mm wide across thorax; paratype from Sta. 4-10 incomplete, with 36 setigers, 6.5 mm long, 0.68 mm wide across thorax. Most segments intact, well-preserved. Thorax with 12 setigers on all specimens, last thoracic segment partially transitional on one paratype (LACM-AHF Poly 11665). Thoracic segments narrow, about 4.5 times as wide as long. Dorsal and ventral ridges and grooves absent. Color in alcohol: light tan.

Pre-setiger region relatively short, about as wide as long, triangular ( Fig. 14 A–B). Prostomium conical, tapering to pointed tip ( Fig. 14 A–B); nuchal organs vertical curved slits on posterior lateral margin ( Fig. 14A ); eyespots absent. Peristomium slightly longer than first setiger, with a single smooth annular ring dorsally ( Fig. 14B ), surrounding mouth ventrally, forming upper and lower lips ( Fig. 14A ).

Thoracic notopodia with a digitiform postsetal lobe, short at first, then becoming long, narrow in posterior thoracic segments ( Fig. 14C ); each notopodial lobe arises from a thick but narrow base. Thoracic neuropodia similar, with postsetal lobe shorter, thicker ( Figs. 14A, C ), arising from a broadly rounded base ( Fig. 14C ). Transition to abdominal segments abrupt, with fewer noto- and neurosetae; notopodial postsetal lobes continuing as narrow and elongate along rest of body ( Fig. 14D ); neuropodium becoming elongate, narrow with apex divided into two parts separated by notch ( Fig. 14D ); each abdominal neuropodium with narrow subpodial flange and 1–2 subpodial papillae on most abdominal segments ( Fig. 14D ).

Branchiae from a posterior thoracic setiger, 11 or 12 ( Fig. 14B ); branchiae full size at first, triangular and smooth, becoming wrinkled in middle segments, tapering to papillate tip ( Fig. 14D ). Branchiae of some middle and posterior setigers with flaglike swelling projecting laterally.

Thoracic notosetae numerous thick, long, camerated capillaries arranged in 4–5 rows. Thoracic neurosetae arranged in about four rows of numerous camerated capillaries and 3–5 uncini in third row. Individual uncini with shafts smooth on convex side, tapering to narrow, rounded tip; concave side of shaft flattened, bearing paired knobs along most of shaft ( Fig. 14E ). Abdominal notosetae thin, camerated capillaries and 1–2 furcate setae. Furcate setae with unequal tynes, each tyne with blunt tip and apical notch; row of thin needles between tynes ( Fig. 14F ). Abdominal neurosetae with up to 4–5 thin capillaries each with short barbs along one edge and a single curved aciculum, sometimes protruding, with rounded tip. Flail setae not observed.

Pygidium short, with a single large ventral lobe, about ten shorter lateral lobes surrounding anal opening, and two short dorsal anal cirri.

Methyl Green stain. No pattern.

Remarks. Scoloplos californiensis n. sp. from off northern California is similar to S. sparsaciculus n. sp. from off Brunei in the South China Sea (see below) in having thoracic neuropodia with relatively few uncini, a subpodial flange and subpodial lobe in abdominal neuropodia, and similar appearing thoracic neuropodial uncini. Both species also have a similar number of thoracic setigers and initiation of the branchiae. The two species differ most importantly in that S. californiensis n. sp. has furcate setae in abdominal notopodia that are absent in S. sparsaciculus n. sp. In addition, the pre-setiger region of S. californiensis n. sp. is about as wide as long instead of narrower and longer than wide and the thoracic segments are up to 4.5 times as wide as long instead of only about 2.5 times as wide as long. A low interramal process is present on a few anterior abdominal setigers of S. sparsaciculus n. sp.; this is absent on S. californiensis n. sp. Up to five uncini are present in thoracic neuropodia of S. californiensis n. sp. compared to up 1–3 in S. sparsaciculus n. sp.

Because one important difference separating S. californiensis n. sp. from S. sparsaciculus n. sp. appeared to be the presence of furcate setae in abdominal notopodia of the former and their absence in the latter, all 20 specimens of S. sparsaciculus n. sp. were re-examined and the absence of furcate setae was confirmed.

Etymology. The species is named for its location offshore California at continental slope depths.

Distribution. Off northern California in middle continental slope depths, 1730–1880 m.

Figures

FIGURE 14. Scoloplos californiensis n. sp. A, anterior end, left lateral view; B, anterior end, dorsal view; C, thoracic setiger 7, left side, posterior view; D, abdominal setiger 16, left side, posterior view; E, thoracic neuropodial uncini; F, furcate seta from abdominal notopodium; G, posterior end, left lateral view. A, C–G holotype (LACM-AHF Poly 11664); B, paratype (LACM- AHF Poly 11665).