Leitoscoloplos geminus Mackie, 1987

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 : 30-32

Leitoscoloplos geminus Mackie, 1987

Figures 12–13

Scoloplos kerguelensis: Monro 1936: 160 (in part). Not McIntosh 1885. Fide Mackie 1987. Leitoscoloplos kerguelensis: Hartmann-Schröder 1986: 82 ; Hartmann-Schröder & Rosenfeldt 1988: 53 (in part); 1990: 105– 106 (in part).

Leitoscoloplos geminus Mackie, 1987: 6 –7, fig. 5.

Material examined. Ross Island, McMurdo Sound, off McMurdo Station, 77°51.067′S, 66°39.880′E, 20 m, in sand and silt, coll. S. Kim and J.A. Blake, 11 Jan 2000, (11, LACM-AHF Poly 8957); same location , 30 m, in sponge mat, coll. S. Kim and J.A. Blake, 15 Jan 2000 (3, LACM-AHF Poly 8958).—Antarctic Peninsula, Hero Sta. 1120 , 25– 31 m (45, USNM 187514 ); Gamma Island , Staten Island Sta. 32-63, coll. W.L. Schmitt , 100 m (1, USNM 46389 ); Anvers Island , Staten Island Sta. 67-63, coll. W.L. Schmitt , 62 m (5, USNM 46390). — South Shetland Islands, Hero Sta. 721-726 (2, USNM 60170 ) ; Sta. 721-742 (6, USNM 60169); Sta. 721-752 (3, USNM 60173); Sta. 721-819 (2, USNM 60171); Sta. 721-965 (2, USNM 60165); Sta. 721-968 (1, USNM 60159); Sta. 721-972 (2, USNM 60158); Sta. 721-975 (3, USNM 60160); Sta. 721-979 (1, USNM 60161); Sta. 721-980 (2 USNM 60168); 721-981 (1, USNM 60163); Sta. 721-983 (7, USNM 60162); Sta. 721-1033 (1, USNM 60164).—Bransfield Strait, Eltanin Sta. 12-1003, 210– 220 m (1, USNM 56522).

Description. A moderate-sized species, up to 28 mm long, 1.5 mm wide for about 85 setigers; average size 25 mm long, 1.2 mm wide for about 65 setigers. Color in alcohol: light tan; color in life: yellow to orange, with light brown pigment around mouth opening (based on personal observations at McMurdo Station, 19 Jan 2000). Thoracic region inflated, not depressed, with 10 setigers (7–9 in juveniles), wider than abdominal segments ( Figs. 12 A, 13A); transition from thorax to abdomen abrupt ( Figs. 12 A, 13A).

Prostomium short, narrow, conical, blunted on tip, not acute ( Figs. 12 A, 13A–B); two nuchal slits in dorsolateral locations ( Fig. 13 B) without eyespots. Peristomium a single achaetous ring, at least twice as wide as long, longer than setiger 1 ( Fig. 12 A).

Thoracic parapodia similar, inconspicuous, with basal cushion from which setae arise; with triangular-shaped notopodial postsetal lobes and more oval-shaped neuropodial postsetal lobes increasing in size along thorax ( Fig. 12 B). Abdominal notopodial postsetal lobes wide basally, tapering to elongate narrow tip ( Figs. 12 C–D, 13C). Neuropodia short, rounded, expanded apically, with small notch from which setae arise; small subpodial flange present ventral to neuropodium, separated by a notch ( Fig. 12 C); in more posterior setigers, a large, blister-like subpodial swelling usually present ventral to neuropodium ( Fig. 12 D).

Branchiae from setiger 11–12 (10 in juveniles), usually 11, very short, inconspicuous; branchiae short, triangular at first ( Fig. 12 C), becoming asymmetrical and irregular in shape in posterior segments ( Fig. 12 D), usually bending medially.

Thoracic setae crenulated capillaries; notosetae arising from single spreading fascicle consisting of two rows, with shortest and thinnest setae in anterior row; neurosetae arising from two fascicles more or less dorsal and ventral to postsetal lobe ( Fig. 12 B); setae of upper fascicle often with dark bases. Abdominal notosetae including crenulated capillaries and 0–2 furcate setae; furcate setae with unequal tynes connected by row of very fine needles as interpreted in light microscopy ( Fig. 12 E); with SEM, individual needles appearing thicker and fewer; tynes with apical openings ( Fig. 13 E). Anterior abdominal neurosetae long, stiff, becoming thinner, posteriorly.

Pygidium a simple ring, lacking cirri ( Fig. 13 D).

Remarks. See comparative remarks under Leitoscoloplos mawsoni .

Distribution. Widespread in shallow Antarctic seas: Ross Sea, McMurdo Sound; South Orkneys, Antarctic Peninsula; South Shetland Islands; 20– 220 m.

Figures

FIGURE 12. Leitoscoloplos geminus (Mackie, 1987). Antarctic Peninsula (USNM 187514). A, anterior end, dorsal view; B, thoracic parapodium, anterior view; C, anterior abdominal parapodium, anterior view; D, posterior abdominal parapodium, anterior view; E, furcate seta.

FIGURE 13. Leitoscoloplos geminus (Mackie, 1987). McMurdo Station, 15 Jan 2000 (SEM, JAB). A, anterior end, left lateral view; B, same, close up of prostomium, peristomium, and nuchal organ; C. middle body segments, dorsal view; D, posterior end, ventrolateral view showing pygidium; E, furcate seta, arrows denote openings on tips of tynes.