Leitoscoloplos rankini, 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 : 36-39

Leitoscoloplos rankini new species

Figures 17–18

Haploscoloplos sp. Hartman 1978: 156 (in part, Glacier Sta. 69-19).

Material examined. Drake Passage, ANDEEP I ANT XIX-3, R/V Polarstern, Sta. PS-61/43- 2, 3959 m (1, SEM, JAB); Sta. PS-61/46- 3, 2888 m (1, ZMH P-27799).—Weddell Sea, Glacier Sta. 69- 19, 11 Mar 1969, 74.105°S, 32.603°W, 1622 m, holotype (USNM 1013903); ANDEEP III ANT XXII-3, R/V Polarstern, Sta. PS-67/121- 6, 2618 m (1, ZMH P-27800).

Description. Holotype posteriorly incomplete, broken into three parts, 22 mm long, 1 mm wide for 50 setigerous segments; 10 thoracic setigers. Specimen from Sta. PS-61, 46-3 complete, 19 mm long, 0.8 mm wide for 80 setigers; with 11 thoracic setigers. Specimen from Sta. PS-67, 110-11 smaller, complete, in two parts, 7 mm long, 0.4 mm wide for 40 setigers; with 9 thoracic setigers.

Thoracic region widest part of body, with 9–11 setigers, rounded in cross section, not depressed ( Fig. 17 B). Transition between thorax and abdomen abrupt ( Fig. 17 A) or with one transitional segment. Abdominal segments becoming narrow in posterior one-third of body. Branchiae from setiger 18–21, small and stubby at first, becoming thin, about twice as long as notopodial postsetal lobes ( Fig. 17 C).

Prostomium conical, pointed; no eyespots ( Figs. 17 A, 18A); nuchal organs as large slit between prostomium and peristomium ( Fig. 18 B). Peristomium with one achaetous ring ( Figs. 17 A, 18A).

Thoracic segments all similar, with prominent postsetal lobes; notopodial postsetal lobes subtriangular ( Fig. 17 B); neuropodial postsetal lobe arising from low postsetal ridge ( Fig. 17 B). Middle and posterior abdominal parapodia dorsally elevated; elevated parapodia fused across dorsum, forming raised dorsal crest from which branchiae arise, best observed in posterior abdominal segments ( Fig. 18 C). Abdominal notopodia with narrow fingerlike postsetal lobe ( Figs. 17 C, 18D); neuropodia elongated, apically expanded, divided into two lobes between which setae arise ( Fig. 17 C); without subpodial flange.

Branchiae short at first ( Fig. 18 C–D), then becoming longer than notopodial lobes in far posterior segments ( Fig. 17 C).

Thoracic setae all crenulated capillaries ( Fig. 18 E); notopodial fascicles with 6–8 setae; neurosetae more numerous, arranged in two dense rows. Abdominal notopodia with 6–9 long capillaries and 3–4 furcate setae; each furcate seta with one tyne shorter than the other, both blunted on tips with apical notch; tynes connected by thin webbing composed of fine needles ( Fig. 17 D). Abdominal neuropodia with long and short capillaries; 1–2 very short and thin aciculae, sometimes protruding. Pygidium with two thin cirri.

Etymology. This species is named for the late Dr. John S. (Stubby) Rankin, Professor Emeritus of the University of Connecticut, friend, and teacher. Dr. Rankin was director of the sampling program during the International Weddell Sea Expedition (1968–69).

Remarks. Leitoscoloplos rankini n. sp. is a deep-sea species belonging to the L. kerguelensis group in having branchiae first present from the anterior abdominal region. The species differs from related forms in the nature of the inflated and elevated parapodia of the posterior abdominal segments. These parapodia are located on the posterior border of the segments and are elevated dorsally to form prominent crests. Further differences with related forms are discussed under L. eltaninae n. sp. (see above).

Distribution. Drake Passage and Weddell Sea, 1622–3959 m.

Figures

FIGURE 17. Leitoscoloplos rankini n. sp. Holotype (USNM 1013903). A, anterior end, right lateral view; B, thoracic parapodium, anterior view; C, posterior abdominal segment, posterior view; D, furcate seta.

FIGURE 18. Leitoscoloplos rankini n. sp. Weddell Sea, ANDEEP I ANT XIX- 3, R / V Polarstern, Sta. PS- 61 / 046 - 3 (SEM, JAB). A, anterior end, dorsal view; B, Anterior end, left lateral view; prostomium, peristomium, and location of nuchal organ; C, middle abdominal segments, dorsal view; D, abdominal parapodium, anterior view; E, thoracic capillary setae.