Notomastus

Notomastus nr. latericeus Sars, 1851

Figures 26 A–B, 27 A–F, 28 A–B

Notomastus latericeus Sars, 1851: 199.

Notomastus latericeus.— Eisig 1887: 861. Fauvel 1927: 143, fig. 49a–h. Fauvel 1953: 364, figs. 189a–h. Day 1967: 599, fig. 28.2a–d. Gallardo 1968: 120, pl. 53, fig. 13. Thomassin 1970: 83 –86, fig. 8a–e. Notomastus near latericeus Green 2002: 299 –301, fig. 18a–j.

Material examined. Oahu Island: Mamala Bay, Sand Island outfall, Sta. C6R2, 21°16ʹ11.4ʺ N, 157°50ʹ31.0ʺ W, 19.5 m, Aug. 2006 (1); Sta. C5AR2, 21°16ʹ53.3ʺ N, 157°51ʹ24.2ʺ W, 20.7 m, Aug. 2002 (1, BPBM R3614); Sta. D2AR2, 21°16ʹ56.5ʺ N, 157°54ʹ35.0ʺ W, 53.3 m, Aug. 2006 (1); Sta. C6R1, 21°16ʹ11.5ʺ N, 157°50ʹ31.2ʺ W, 19.2 m, Aug. 2006 (2); Sta. C5AR2, 21°16ʹ53.3ʺ N, 157°51ʹ24.2ʺ W, 20.7 m, Aug. 2006 (1); Sta. E3R1, 21°16ʹ44.0ʺ N, 157°53ʹ49.4ʺ W, 82.6 m, Aug. 2002 (1); Mamala Bay, Barbers Point outfall, Sta. HB7R1, 21°15ʹ30.5ʺ N, 158°03ʹ11.4ʺ W, 65.2 m, Feb. 2006 (4, BPBM R3613); Sta. HB2R2, 21°17ʹ0 0.1ʺ N, 158°01ʹ21.3ʺ W, 60.0 m, Feb. 2006 (1); Sta. HB6R3, 21°16ʹ33.3ʺ N, 158°01ʹ48.3ʺ W, 59.4 m, Feb. 2006 (1); Sta. HB3R4, 21°16ʹ52.0ʺ N, 158°01ʹ30.5ʺ W, 68.0 m, Mar. 2000 (1); Sta. HB1R4, 21°16ʹ50.5ʺ N, 157°59ʹ19.7ʺ W, 65.2 m, Feb. 2006 (1); Sta. HB7R1, 21°15ʹ30.5ʺ N, 158°03ʹ11.4ʺ W, 65.2 m, Jun. 1993 (1, BPBM R3612); Sta. HZR4, 21°16ʹ53.1ʺ N, 158°01ʹ30.3ʺ W, 62.5 m, Feb. 2000 (1, BPBM R3615); Sta. HB2R4, 21°17ʹ0 0.5ʺ N, 158°01ʹ21.2ʺ W, 59.1 m, Feb. 2000 (1); Sta. HB7R2, 21°15ʹ30.4ʺ N, 158°03ʹ11.3ʺ W, 67.1 m, Feb. 2000 (1); Sta. HB2R5, 21°17ʹ0 0.4ʺ N, 158°01ʹ21.5ʺ W, 59.4 m, Feb. 2003 (1, BPBM R3611); Sta. HB6R1, 21°16ʹ33.1ʺ N, 158°01ʹ48.1ʺ W, 59.4 m, Feb. 2000 (1); Sta. HB6R3, 21°16ʹ33.3ʺ N, 158°01ʹ48.3ʺ W, 59.4 m, Feb. 2001 (1); Sta. HB7R2, 21°15ʹ30.4ʺ N, 158°03ʹ11.3ʺ W, 67.4 m, Jun. 1993 (1); Waianae outfall, Sta. ZR3, 21°25ʹ22.9ʺ N, 158°11ʹ51.1ʺ W, 35 m, May 2001 (1).

Description. Complete specimen 10 mm long, 0.1 mm wide (mid-thorax) for about 74 chaetigers. Largest specimen incomplete, about 46 mm long, 0.2 mm wide (mid-thorax) for about 90 chaetigers. Body widest on thoracic chaetigers 5–6, tapering to abdominal segments and posterior end. Body divided into three parts: 1) thoracic segments biannulate, several times wider than long (Figs 26 A, 27A, B); 2) anterior abdominal segments with enlarged and raised neuropodial lobes covering sides laterally and approaching each other ventrally; notopodial lobes reduced and approaching each other mid-dorsally (Figs 26 A, B, 27A–D); 3) neuropodial lobes reduced and not covering lateral sides, notopodial lobes further apart from each other (Fig. 27 E). Color in alcohol pale to tan yellow, no distinct pigmentation.

Prostomium conical, retracted in all specimens with short palpode (Fig. 26 A). Nuchal organs not observed; 8–10 varying size eyespots present. Everted proboscis with numerous papillae throughout. Peristomium achaetous, as long as chaetiger 1 (Figs 26 A, 27B).

Thorax with 11 chaetigers; chaetigers 1–6 expanded, following thoracic chaetigers tapering to beginning of abdomen (Figs 26 A, 27B). Thoracic chaetigers biannulated, with inter-segmental groove after chaetigers 4–5 (Fig. 26 A). Thorax with bilimbate capillaries only; notopodia inserted dorsally, neuropodia laterally. Lateral organs observed between noto- and neuropodia after chaetiger 7 (Fig. 27 D). Genital pores observed throughout the abdomen; one specimen with protruding eggs (Fig. 27 D).

Transition between thorax and abdomen marked by constriction, methyl green staining and changes in chaetae (Figs 26 B, 27A–C, 28A, B); abdominal chaetigers with hooded hooks throughout. Notochaetae of last thoracic chaetiger inserted in enlarged tori (Fig. 27 A); following abdominal notopodia approach each other mid-dorsally and appear as a single torus (Fig. 27 D). Neuropodial lobes enlarged laterally, superior edge inflated and perhaps with branchial function (Figs 26 B, 27C); neuropodial lobes more developed on anterior abdominal segments, becoming restricted to small lateral tori posteriorly (Fig. 27 E). Notopodial lobes also further apart posteriorly. Abdominal notopodia with 4–6 hooded hooks throughout; neuropodia anteriorly possessing over 150 hooks and reducing to 20–22 hooks on posterior chaetigers. Hoods short extending slightly beyond main fang. Hooks with multiple teeth, in frontal view with at least two rows of teeth; 4–5 in basal row and 3–4 in superior row (Fig. 27 F). Branchiae absent, but expanded neuropodial lobes on anterior end of abdomen may have branchial function (Hartman 1947). Pygidium simple, without appendages; anal aperture terminal (Fig. 27 E).

Methyl green staining pattern. Prostomium, peristomium and thorax deeply stained; prostomium darkest, chaetigers 1–2 with 3–4 dorsal bands; staining on thorax darker posterior to chaetiger 6. Transition between thorax and abdomen marked by dark green rings, chaetiger 11 and 12 each with two rings (Fig. 28 B). Abdominal lateral organs staining dark green throughout. Abdominal segments with distinct transverse rings in inter-segmental regions, also encircle pre- and post-chaetal lobes (Fig. 28 A); very posterior abdominal segments before pygidium without banding.

Distribution. This species has been reported from worldwide localities (Green, 2002).

Remarks. The material from Hawaii agrees well with descriptions of Notomastus near latericeus sensu Green (2002). This author discusses the possibility of more than one species having been referred to as N. latericeus in the literature by the distinct dentition of the abdominal hooks. Although we believe this may be true, SEM analysis would be required to observe these dentitions to confirm this. The MGSP of the specimens described herein is slightly distinct from that reported in Green (2002); in the Hawaiian material, the entirety of chaetigers 11 and 12 are stained (see Fig. 28 A, B) while only the postchaetal region of chaetiger 11 and the prechaetal region of chaetiger 12 are intensely stained in Green (2002).