Leitoscoloplos lunulus, 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 : 12-15

Leitoscoloplos lunulus new species

Figures 5–6

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Leitoscoloplos sp. 1: Hilbig & Blake 2006: 265.

Material examined. Continental slope off northern California, off Half Moon Bay , U.S EPA 102 Site selection

Survey, R / V Point Sur, coll. J.A. Blake, south of Pioneer Canyon, Sta. 4-8. 18 Sep 1991, 37°13.85′N, 123°13.50′W, 1560 m, holotype ( LACM-AHF Poly 11660) ; north of Pioneer Canyon , Sta. 3-4, 14 Sep 1991, 37°27.83′N, 123°11.60′W, 1030 m, 1 paratype in two pieces ( LACM-AHF Poly 11661) ; Sta. 3-7, 14 Sep 1991, 37°27.44′N, 123°19.50′W, 1675 m, 1 paratype ( CASIZ 234041 ) ; Sta. 3-16, 15 Sep 1991, 37°23.20′N, 123°14.44′W, 1220 m, 1 paratype ( CASIZ 234048 ) .

Description. A small species, holotype (LACM-AHF Poly 11660) complete, with 50 setigers, 6.8 mm long, 0.45 mm wide across thoracic segments; paratype from Sta. 3-4 (LACM-AHF Poly 11661), smaller, mostly complete, with 34 setigers, 4.1 mm long. Body thickened in thoracic region with smooth rectangular-shaped segments about 4.6 times wider than long; abdominal segments becoming narrower and shorter. Thoracic segments uniannulate with narrow intersegmental groove ( Fig. 5A ); abdominal segments becoming biannulate due to narrow ring developing on posterior segmental margin. Dorsal and ventral longitudinal ridges or grooves absent. Color in alcohol: light tan.

Pre-setiger region short, compact, slightly wider than long, longer than first two setigers ( Fig. 5 A–B). Prostomium semi-circular in shape, narrowing to broadly rounded apex in dorsal and ventral views ( Fig. 5 A–B); narrower in lateral view ( Fig. 5C ); eyespots absent; nuchal organs elongate lateral opening on posterior margin ( Fig. 5C ). Peristomium appearing entire in dorsal view ( Fig. 5A ); with single ventrolateral groove ( Fig. 5 B–C). Anterior margin sculpted especially on lower lip of mouth ( Fig. 5B )

Thorax with nine setigers, abruptly changing to abdominal segments with development of elongated neuropodium and loss of most neurosetae ( Fig. 5A ). Thoracic notopodial and neuropodial postsetal lamellae both elongate, digitiform, tapering to narrow apex; arising from broadly rounded base ( Fig. 5E ). Abdominal notopodia short, triangular, with long, thin, digitiform postsetal lamella ( Fig. 6 A–B). Abdominal neuropodia thickened lobes, short at first surrounded by thick basal flange ( Fig. 6A ); subsequent neuropodia long, narrow, with low subpodial flange on body wall below neuropodial base ( Fig. 6B ); subpodial papillae absent. Neuropodia with rounded apex and short, narrow ventral cirrus with rounded tip ( Fig. 6 A–B).

Branchiae from setiger 14 in holotype and setigers 14–15 in paratypes. Branchiae full size from initiation, weakly triangular at first, tapering to rounded tip ( Fig. 6A ); branchiae of middle and posterior setigers thicker, more fleshy in appearance with expansion, narrowing to papillate tip ( Fig. 6B ). Each branchia as long as or slightly longer than notopodial postsetal lamella.

All setae camerated capillaries except neuropodial aciculae; furcate and flail setae absent. Thoracic noto- and neurosetae long, crowded capillaries numbering about 14–16, arranged in two weakly defined rows. Abdominal notosetae include 7–8 capillaries, some long; abdominal neurosetae include 4–5 capillaries and 1–2 short, narrow protruding pointed aciculae.

Pygidium with two dorsal, four lateral, and one large ventral lobe surrounding anal opening. Two thin, digitiform anal cirri arising from dorsal lobes ( Fig. 5D ).

Methyl Green stain. No pattern, body stains uniformly and de-stains rapidly.

Remarks. Leitoscoloplos lunulus n. sp. is another member of the L. kerguelensis group as defined by Blake (2017) in having branchiae first present from an anterior abdominal setiger. L. lunulus n. sp. is one of five species in the eastern Pacific belonging to this group and as noted in the previous account, is most closely related to L. gordaensis n. sp. by lacking furcate setae and having a short pre-setiger region where the prostomium is distinctly separated from the peristomium by a groove. In L. lunulus n. sp. the groove that separates the prostomium and peristomium is sculpted rather than smooth and the thorax has nine setigers instead of ten.

Etymology. The epithet is from the Latin, lunula, for moon, in relation to the survey location off Half Moon Bay, California.

Distribution. Off northern California, middle continental slope depths, 1020–1760 m.

Figures

FIGURE 5. Leitoscoloplos lunulus n. sp. A, anterior end, dorsal view; B, anterior end, ventral view; C, anterior end, right lateral view; D, pygidium, right lateral view; E, thoracic setiger 7, right, posterior view. A–B, D holotype (LACM-AHF Poly 11660); C, E, paratype (CASIZ 234041).

FIGURE 6. Leitoscoloplos lunulus n. sp. Holotype (LACM-AHH Poly 11660): A, anterior abdominal setiger 16, right, lateral anterior view; B, posterior abdominal setiger, left, lateral anterior view.