Leitoscoloplos nasus, Blake, James A., 2017

Blake, James A., 2017, Polychaeta Orbiniidae from Antarctica, the Southern Ocean, the Abyssal Pacific Ocean, and off South America, Zootaxa 4218 (1), pp. 1-145 : 32-34

Leitoscoloplos nasus new species

Figure 14

Material examined. Antarctic Peninsula, Eltanin Station 6-439, 0 9 Jan 1963, 63.83°S, 62.60°W, 128–165 m, holotype and 3 paratypes, USNM 1407121–2 ).

Description. All specimens posteriorly incomplete; holotype 8.7 mm long, 0.6 mm wide, for 37 segments; largest paratype 8.3 mm long, 0.35 mm wide for 33 segments. Body rounded in cross section, with thoracic region slightly inflated. Thorax with 9–10 setigers, with each segment wider than long ( Fig. 14 A–B). Transition from thorax abrupt, denoted by reduction in number of neurosetae and change in form of neuropodial postsetal lobes. Abdominal segments narrow at first, then becoming elongate, nearly twice as long as wide with parapodia at posterior end of each elongated segment ( Fig. 14 C). Color in alcohol: brown.

Prostomium elongate, more than twice as long as wide; tapering anteriorly to narrow, rounded tip, sometimes curved dorsally; eyespots absent; with paired nuchal organs. Peristomium short asetigerous ring, together with prostomium forming unusually elongate “head” ( Fig. 14 A–B)

Thoracic notopodia short, papillate on setiger 1 and sometimes setiger 2, then becoming long, fingerlike over remaining thoracic setigers; abdominal notopodia elongate, becoming narrow more posteriorly ( Fig. 14 C–D). Thoracic neuropodia similar to notopodial lamellae, but overall shorter and more triangular. Abdominal neuropodia, short, thickened basally, notched distally; with subpodial flange ( Fig. 14 D).

Thoracic setae all long crenulated capillaries. Abdominal notopodia with 6–8 crenulated capillaries and 1–2 furcate setae; furcate setae with thin needles forming web between subequal tynes; barbs on shaft not apparent in light microscopy ( Fig. 14 E). Abdominal neuropodia with 2–3 thin, non-crenulated capillaries ( Fig. 14 D).

Branchiae from setiger 13–14, continuing to end of fragment; each branchia short, narrowing to rounded apex, barely longer than notopodial lobes in thoracic segments, shorter in abdominal segments ( Fig. 14 D). Pygidium unknown.

Etymology. The epithet is derived from the Latin nasus (m), for nose, to denote the usually elongate and narrow prostomium-peristomium that characterizes this species.

Remarks. Leitoscoloplos nasus n. sp. is another Antarctic species in the L. kerguelensis group with a reduced number of thoracic setigers and branchiae from anterior abdominal segments. The species is easily recognized and distinguished from other species of the genus in Antarctica and elsewhere by the elongate and unusually narrow “head” consisting of the prostomium-peristomium, and by the long, narrow abdominal segments. Leitoscoloplos drakei described below also has elongate abdominal segments, but this species is thin and threadlike with branchiae limited to far posterior segments.

Distribution. Antarctic Peninsula, 128– 165 m.

Figures

FIGURE 14. Leitoscoloplos nasus n. sp. Paratype, (USNM 1407122), A, anterior end, left lateral view; B, anterior end, dorsal view; C, middle body segments, dorsal view; D, abdominal parapodium, anterior view; E, furcate seta.