Scoloplos suroestense, 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 : 47

Scoloplos suroestense new species

Figures 23 G–H, 24

Material examined. Juan Fernandez Islands , Chile Bay behind Punta Suroestense , Anton Bruun Cruise 12, Sta. 134, 13 Dec 1965, 33°34′S, 78°55′W, shallow subtidal (<5m), holotype and 3 paratypes ( USNM 1013917–8 ).

Description. Holotype complete, 12 mm long and 1.2 mm wide for approximately 100 segments; paratypes smaller, up to 75 segments. First four thoracic segments distinctly inflated, due to inverted proboscis visible dorsally through body wall ( Figs. 23 G, 24A–B); following thoracic segments distinctly depressed ( Figs. 23 A, 24B– C); abdominal segments rounded in cross section ( Fig. 24 D). Thorax with 10–15 setigers, depending upon size of specimens; smallest specimens with fewest thoracic segments, larger specimens with most thoracic segments; last 1–2 thoracic segments appearing transitional with abdominal region in having fewer, more tightly grouped setae. Color in alcohol: light tan.

Prostomium triangular, pointed anteriorly ( Figs. 23 G, 24A–B); no eyespots; with two ciliated dorsolateral nuchal organs on posterior border with peristomium of holotype ( Fig. 24 A); with SEM, nuchal organ of paratype a slit ( Fig. 23 A). Peristomium with a single achaetous ring completely fused to setiger 1.

Thoracic parapodia with digitiform postsetal lobes from setiger 1 ( Fig. 24 A–B); neuropodial lobes slightly shorter than notopodial lobes. Anterior abdominal postsetal lobes similar to those of thoracic region, with neuropodial lobes becoming reduced to short papillae in middle body segments; notopodial lobes remaining long, but shorter than branchiae ( Fig. 24 D). No interramal or subpodial lobes present.

Notosetae all crenulated capillaries throughout; furcate setae entirely absent. Thoracic neurosetae including 8– 9 uncini located anterior to 12–14 crenulated capillaries ( Figs. 23 H, 24C); uncini slender, no broader than capillaries, with blunted curved tips partially covered by hyaline hood ( Fig. 24 E–F), in SEM hood appearing as a sheath extending from tip of shaft posteriorly ( Fig. 23 H); shafts with ribs that in light microscope and SEM consist of transverse rows of barbs ( Figs. 23 H, 24E–F), capillaries with transverse rows of barbs ( Figs. 23 H, 24G). Abdominal neurosetae including 2–3 straight pointed uncini ( Fig. 24 H) and 3–4 capillaries.

Branchiae from setiger 12–17 or first 1–2 abdominal segments ( Fig. 24 B).

Pygidium with terminal anus, encompassed by broad, thickened lobe, without anal cirri.

Remarks. Scoloplos suroestense n. sp. is unusual among species of Scoloplos in having branchiae first present from anterior abdominal setigers. In this regard, the species is closely related to S. normalis ( Day, 1977) and S. difficilis Day, 1977 , both from Australia ( Hartman 1957; Day 1977; Mackie 1987). Scoloplos normalis , originally described in the genus Leitoscoloplos by Day (1977), was transferred to Scoloplos by Mackie (1987) after he discovered that the paratypes had a few short, robust and weakly serrated uncini with a close adhering hood among neuropodial capillaries of the first three thoracic setigers; one small specimen had uncini distributed over a greater range of setigers. Scoloplos suroestense n. sp., in contrast, has 8–9 uncini and 12–14 capillaries in all thoracic neuropodia. Further the uncini of S. suroestense n. sp. have rows of barbs all along the shaft and bear a thin hyaline sheath at the tip. The nature of the thoracic neuropodial uncini on S. suroestense n. sp. also differs from the smooth shafted uncini reported by Day (1977) for S. difficilis .

Etymology. The epithet is taken from Punta Suroestense , near the type locality in the Juan Fernandez Islands.

Distribution. Juan Fernandez Islands, shallow subtidal.

Figures

FIGURE 23. Scoloplos bathytatus n. sp. (ANDEEP III Sta. PS / 121 - 12). A, anterior end, left lateral view; B, second specimen, left lateral view; C, nuchal organ detail from B, not to scale; D, thoracic neuropodial uncini; E, abdominal parapodium, anterior view; F, furcate seta, arrows denote openings on tip of tynes. — Scoloplos suroestense. Paratype (USNM 1013918). G. anterior end, left lateral view; H, thoracic neuropodial uncini.

FIGURE 24. Scoloplos suroestense n. sp. Holotype (USNM 1013917). A, anterior end, dorsal view; B, anterior end, left lateral view; C, thoracic parapodium, anterior view; D, abdominal parapodium, anterior view; E – F, thoracic neuropodial uncini; G, thoracic neuropodial capillary seta; H, abdominal neuroseta.