Leitoscoloplos williamsae, 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 : 17-19

Leitoscoloplos williamsae new species

Figures 8–9

urn:lsid:zoobank.org:act:8CBB5BCD-91E0-4077-9803-095212E75A95

Leitoscoloplos sp. 3 and sp. 4: Hilbig & Blake 2006: 265.

Material examined. Continental slope, off northern California, off Half Moon Bay, U.S EPA Site selection Survey, R / V Point Sur, coll. J.A. Blake, south of Pioneer Canyon, Sta. 4-10, 17 Sep 1991, 37°11.26′N, 123°15.26′W, 1760 m, holotype ( LACM-AHF Poly 11658) ; North of Pioneer Canyon , Sta. 3-19, 16 Sep 1991, 37°26.05′N, 123°19.99′W, 1760 m, 1 paratype ( LACM-AHF Poly 11659)

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Description. A moderate-sized species, holotype complete, 10.5 mm long, 0.6 mm across thoracic segments for 65 setigers; paratype mostly complete, 5.7 mm long, 0.25 mm across thorax for 40 setigers. Body elongate, more or less consistently same width throughout, tapering to narrow posterior end. Thoracic segments about 3.5 times as wide as long, each separated from one another by prominent intersegmental grooves, grooves with an elevated transverse dorsal ridge or hump ( Fig. 8 A–B) producing a biannulate appearance; lateral and ventral grooves not as conspicuous. Anterior abdominal segments narrow, becoming longer, about twice as wide as long in middle and posterior segments. Anterior and middle abdominal segments with intersegmental groove transformed into a flattened band producing a biannulate appearance, band obscured in posterior abdominal segments. Longitudinal grooves or ridges along body absent. Color in alcohol: light tan.

Pre-setiger region triangular, longer than wide, narrowing anteriorly ( Fig. 8 A–B). Prostomium conical, tapering to narrow apex ( Fig. 8A ); nuchal organs narrow, crescent-shaped on posterior lateral margin ( Fig. 8B ); eyespots absent. Peristomium composed of a single, smooth achaetous ring, ventrally surrounding mouth, inflated dorsally, with no transverse grooves ( Fig. 8 A–B).

Thorax with nine setigers on holotype, transitioning to abdominal segments over 1–2 segments; paratype with eight thoracic setigers. Boundary between last thoracic and first abdominal setiger demarcated by loss of most neurosetae and increase in size of neuropodial lobe. Thoracic notopodial and neuropodial lobes elongate, digitiform, both similar in form arising from broad rounded base ( Fig. 8D ); notopodia of anterior abdominal segments becoming thickened, elongate ( Fig. 9A ); posterior notopodia narrower, tapering to pointed tip ( Fig. 9B ). Anterior abdominal neuropodia thickened, with rounded terminal lobe and short ventral cirrus ( Fig. 9A ); middle and posterior abdominal neuropodia longer, narrow, with short ventral cirrus and bulbous subpodial flange ( Fig. 9B ).

Branchiae first present from setiger 17 in holotype and setiger 18 in paratype; branchiae moderately sized at first, triangular in shape ( Fig. 9A ), becoming longer and thicker in middle abdominal segments ( Fig. 9B ). Branchiae of some far posterior abdominal segments of holotype asymmetrical, with a lateral flaglike extension.

Notosetae include camerated capillaries throughout; furcate and flail setae absent. Thoracic notosetae numbering about 25 per fascicle, arranged in two or three rows. Abdominal notosetae narrow camerated capillaries numbering 8–12 in anterior abdominal segments, reduced to 5–10 posteriorly. Thoracic neurosetae all capillaries, numbering about 20–25 per fascicle in at least two rows. Abdominal neurosetae include 3–5 thin capillaries and 1–2 short protruding aciculae, these minute, with rounded apex ( Fig. 9A ).

Pygidium bluntly rounded, bearing two thin elongate cirri dorsal to the anal opening ( Fig. 8C ).

Methyl Green stain. No pattern; prostomium not staining, rest of body staining uniformly, de-stains rapidly.

Remarks. Leitoscoloplos williamsae n. sp. superficially resembles L. cliffordi n. sp. in having a narrow, elongate pre-setiger region and maximally nine thoracic setigers. However, there are several important differences between the two species: L. cliffordi n. sp. has lateral grooves on the peristomium; a longitudinal ventral groove along the body; thoracic parapodial postsetal lobes are short and digitiform; branchiae are first present from setigers 15–16; notopodial furcate setae with blunt, unequal tynes are present; abdominal neuropodia become short and thick in posterior segments and abdominal neuropodia lack a subpodial flange; L. williamsae n. sp. has a peristomium with no lateral grooves; longitudinal grooves along the body are absent; thoracic postsetal lobes are long and digitiform; branchiae are first present from setigers 17–18; notopodial furcate setae are absent; abdominal neuropodia are long and digitate throughout; and abdominal neuropodia of middle and posterior segments have a bulbous subpodial flange.

Etymology. This species is named for my friend and long-time colleague, Isabelle P. (Izzie) Williams. Ms. Williams was part of the field team for the site-selection survey on which this species was collected and most of the following monitoring surveys at the SF-DODS site. Ms. Williams was also senior taxonomist on these projects, identifying the crustaceans and molluscs, and managed the benthic database.

Distribution. Off northern California in middle continental slope depths, 1760 m.

Figures

FIGURE 8. Leitoscoloplos williamsae n. sp. Holotype (LACM-AHF Poly 11658):A, anterior end, dorsal view; B, anterior end, left lateral view; C, posterior end, right lateral view; D, thoracic setiger 7, right posterior view.

FIGURE 9. Leitoscoloplos williamsae n. sp. Holotype (LACM-AHF Poly 11658): A, abdominal setiger 20, left side, anterior view; B, abdominal setiger 32, right side, anterior view.