Notomastus tenuis Moore, 1909

Magalhães, Wagner F. & Bailey-Brock, Julie H., 2012, Capitellidae Grube, 1862 (Annelida: Polychaeta) from the Hawaiian Islands with description of two new species, Zootaxa 3581, pp. 1-52 : 39-41

Notomastus tenuis Moore, 1909

Figures 28 C–E, 29 A–D, 30 A–F

Notomastus tenuis Moore, 1909: 277 –278, pl. 9, fig. 55.

Notomastus (Clistomastus) tenuis .— Hartman 1947: 420 –422, pl. 47, figs. 1–5. Hartman 1961: 35. Hartman 1966: 405. Hartman 1969: 397–398, figs. 1–5.

Notomastus tenuis .— Blake 2000: 85 –86, fig. 4.15.

? Notomastus (Clistomastus) anoculatus Hartmann-Schröder 1965: 150 –151, fig. 78.

Material examined. Oahu Island: Mamala Bay, Sand Island outfall, Sta. C5AR1, 21°16ʹ53.5ʺ N, 157°51ʹ24.1ʺ W, 20.4 m, Aug. 2007 (1); Sta. C1AR1, 21°17ʹ39.0ʺ N, 157°55ʹ28.1ʺ W, 18.9 m, Aug. 2002 (2, BPBM R3617); Sta. D2R1, 21°16ʹ56.8ʺ N, 157°54ʹ35.6ʺ W, 53.3 m, Aug. 2007 (2, BPBM R3618); Sta. D6R2, 21°16ʹ0 2.1ʺ N, 157°50ʹ45.8ʺ W, 49.4 m, Aug. 2007 (1); Sta. C2R2, 21°17ʹ21.8ʺ N, 157°54ʹ36.5ʺ W, 18.3 m, Aug. 1992 (1); Sta. E5R1, 21°16ʹ22.7ʺ N, 157°51ʹ40.9ʺ W, 101.5 m, Aug. 2006 (1); Sta. D2R2, 21°16ʹ56.5ʺ N, 157°54ʹ35.0ʺ W, 53.3 m, Aug. 2006 (1); Sta. C1AR1, 21°17ʹ39.0ʺ N, 157°55ʹ28.1ʺ W, 18.9 m, Aug. 2006 (1); Sta. C6R2, 21°16ʹ11.4ʺ N, 157°50ʹ31.0ʺ W, 19.5 m, Aug. 2006 (1); Sta. D3R2, 21°16ʹ55.5ʺ N, 157°53ʹ49.3ʺ W, 50.9 m, Aug. 2006 (1); Sta. D2R2, 21°16ʹ56.5ʺ N, 157°54ʹ35.0ʺ W, 53.3 m, Aug. 2002 (3, BPBM R3621); Mamala Bay, Barbers Point outfall, Sta. HZR5, 21°16ʹ53.7ʺ N, 158°01ʹ29.7ʺ W, 62.8 m, Mar. 2003 (1, BPBM R3620); Sta. HB2R1, 21°17ʹ0 0.5ʺ N, 158°01ʹ21.1ʺ W, 58.8 m, Mar. 2003 (1); Sta. HB3R4, 21°16ʹ52.0ʺ N, 158°01ʹ30.5ʺ W, 68.0 m, Mar. 2004 (1); Sta. HB4R5, 21°16ʹ47.0ʺ N, 158°01ʹ38.0ʺ W, 63.1 m, Sept. 1993 (1); Sta. HB4R1, 21°16ʹ46.9ʺ N, 158°01ʹ38.1ʺ W, 63.7 m, Mar. 2001 (1); Sta. HZR3, 21°16ʹ53.7ʺ N, 158°01ʹ30.8ʺ W, 62.8 m, Sept. 1993 (1); Waianae outfall, Sta. ZER6, 21°25ʹ23.3ʺ N, 158°11ʹ47.5ʺ W, 30 m, May 2002 (1, BPBM R3619); Sta. W9R2, 21°26ʹ29.4ʺ N, 158°12ʹ16.3ʺ W, 33 m, May 2007 (1); Sta. ZR1, 21°25ʹ22.9ʺ N, 158°11ʹ51.1ʺ W, 35 m, Jun. 2011 (1); Sta. W9R4, 21°26ʹ29.4ʺ N, 158°12ʹ16.3ʺ W, 33 m, Jun. 1991 (1); Sta. W2R3, 21°24ʹ46.5ʺ N, 158°11ʹ45.6ʺ W, 27 m, Jun. 2011 (1); Kailua Bay, Mokapu outfall, Sta. DR1, 21°25ʹ32.3ʺ N, 157°42ʹ53.6ʺ W, Mar. 2008 (1); Sta. DR4, 21°25ʹ32.3ʺ N, 157°42ʹ53.6ʺ W, Mar. 2008 (3); Sta. DR3, 21°25ʹ32.3ʺ N, 157°42ʹ53.6ʺ W, Mar. 2008 (2); Kaneohe Bay, Coconut Island, Little Beach, in sand with Arenicola brasiliensis , 0 4 Mar. 1983, coll. J.H. Bailey-Brock (1, BPBM R3616); off Honolulu, 495 m, 11 Aug. 1976 (1, BPBM R1732; 1, BPBM R1740). Kauai Island: off Port Allen, 384 m (2, BPBM R1708).

Description. Complete specimens 20–27 mm long, 0.2–0.25 mm wide (mid-thorax) for 81–127 chaetigers. Largest specimen incomplete, in several fragments about 145 mm long, 0.7 mm wide (mid-thorax) for over 300 chaetigers. Body elongate, slender, widest on thoracic chaetiger 5 tapering from abdominal segments to pygidium. Body divided into three regions, with thoracic chaetigers short, anterior abdominal segments long and with raised parapodial lobes that become short and crowded posteriorly ( Fig. 29 A). Color in alcohol variable but tan yellow in some small anterior fragments; most large specimens dark brown and sometimes purplish on anterior abdominal chaetigers.

Prostomium depressed, usually withdrawn, conical with short digitate palpode ( Figs 29 A, 30A). Nuchal organs not observed. Eyespots present, 12–15 on each side in two irregular rows ( Fig. 29 A); sometimes hidden underneath peristomial ring or absent (possibly faded). Everted proboscis in two folds, smooth proximally with papillae present on distal end. Peristomium achaetous, slightly longer than chaetiger 1.

Thorax with 11 chaetigers; chaetiger 1 with notochaetae only; parapodia reduced throughout ( Figs 29 A, 30A). Chaetigers 1–5 slightly expanded, tapering to beginning of abdomen. Thoracic chaetigers biannulated with deep inter-segmental grooves posterior to chaetiger 4 ( Figs 29 A, 30A). Thorax with bilimbate capillaries only; notopodia dorsal, neuropodia lateral, forming well pronounced lateral shoulders in large specimens ( Figs 28 C, 29A, 30A). Lateral organs present throughout thorax and abdomen, closer to notopodia ( Figs 29 A, 30A–C). Genital pores not observed.

Transition between thorax and abdomen marked by slight constriction and changes in chaetae ( Fig. 29 A); abdominal chaetigers with hooded hooks throughout. Abdominal noto- and neuropodia well separated (Fig. 30B). Notopodial lobes approaching each other dorsally, with enlarged lobes posteriorly ( Figs 28 E, 29B–D, 30D). Lateral neuropodial lobes well-separated ventrally ( Figs 28 E, 29B–C, 30D). Anterior thoracic notopodia with 10–12 hooded hooks reducing to 3–4 hooks in far posterior end; neuropodia anteriorly with 12–14 hooks, reducing to 5–6 hooks in far posterior chaetigers. Hoods short, extending slightly beyond main fang (Fig. 30F). Hooks with multiple teeth; with 5–7 teeth above main fang in lateral view, at least three rows of teeth in frontal view; 5–7 in basal row, 4–5 in superior rows (Fig. 30F).

Branchiae absent, but expanded parapodial lobes on abdomen may have branchial function ( Hartman 1947). Pygidium simple, without appendages; anal aperture placed terminally ( Figs 29 D, 30E).

Methyl green staining pattern. Staining variable, prostomium and anterior five thoracic chaetigers may or may not stain ( Fig. 28 C). Staining usually becomes darker towards posterior of the thorax ( Fig. 28 C). An unstained ventral line extends throughout the body and forms a Y transversing the peristomium laterally. Abdomen lightly stained with irregularly spaced speckles ( Fig. 28 D). Dark speckles present on the posterior edge of abdominal segments ( Fig. 28 D). Darkly pigmented specimens stained light green throughout.

Distribution. This species is commonly found in the eastern Pacific, from Washington to southern California in intertidal to shelf depths ( Hartman 1947; Blake 2000). The occurrence in Oahu, Hawaii is the western most record of this species in the Pacific Ocean.

Remarks. This species has been misidentified as Capitellethus cinctus in unpublished reports of the Hawaiian fauna (e.g. Ambrose et al. 2010 and references therein) due to the relative similarity of the anterior end, especially the presence of several eyespots at each side of the prostomium and lack of neurochaetae on chaetiger 1 in both species. The material described herein agrees well with those from Californian waters described by previous authors (e.g. Hartman 1947; Blake 2000). The shape of the abdominal parapodial lobes, especially in the posterior chaetigers is very characteristic of this species and may readily distinguish it from other Notomastus species. The MGSP is not very distinct and apparently differs among specimens in the Hawaiian material.

Type material of Notomastus (Clistomastus) anoculatus Hartmann-Schröder 1965 described from Kaneohe Bay (Oahu, Hawaii) was not available for study but photos of the incomplete holotype were examined and the general appearance of the anterior end and thoracic segments resembles N. tenuis . In addition, the larger specimen found was collected intertidally at Kaneohe Bay which is the type locality for N. anoculatus and agrees very well with N. tenuis . Eyes were not always present in all specimens from Hawaii and this was the main character that led Hartmann-Schröder (1965) to erect this new species. However, it would be unwise to place N. anoculatus as a synonymous of N. tenuis because an actual examination of the holotype, including observation of the hooded hooks, was not possible. The other Notomastus species present in Hawaiian waters differs significantly from N. tenuis in having inflated neuropodial lobes on its abdomen.

Figures

FIGURE 28. Notomastus nr. latericeus: A, MGSP of complete specimen; B, MGSP of transitional segments between thorax and abdomen. Notomastus tenuis: C, MGSP of anterior end in lateral view; D, MGSP of anterior abdominal segments in dorsolateral view; E, posterior abdominal segments of preserved specimen showing expanded parapodial lobes. Holotype of Notomastus anoculatus: F, anterior end in lateral view.

FIGURE 29. Notomastus tenuis: A, anterior end in lateral view; B, posterior abdominal segments with expanded parapodial lobes; C, cross-section of a modified posterior abdominal segment in frontal view, detail of gut region omitted; D, posterior end segments with pygidium.