Capitellethus cinctus Thomassin, 1970

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 : 19-23

Capitellethus cinctus Thomassin, 1970

Figures 13 A–C, 14 A–F, 15 A–D

Capitellethus cinctus Thomassin, 1970: 77 –79, fig. 4.

Capitellethus cinctus .— Green 2002: 278 –280, fig. 9a–i.

Material examined. Oahu Island: Mamala Bay, Sand Island outfall, Sta. E6R2, 2115ʹ50.8ʺ N, 15750ʹ57.9ʺ W, 102.1 m, Aug. 2000 (1, BPBM R3599); Sta. E2R3, 2116ʹ43.4ʺ N, 15754ʹ39.1ʺ W, 101.2 m, Aug. 2007 (1); Sta. E3R1, 2116ʹ44.0ʺ N, 15753ʹ49.4ʺ W, 82.6 m, Aug. 2000 (1); Sta. D2R2, 2116ʹ56.5ʺ N, 15754ʹ35.0ʺ W, 53.3 m, Aug. 2000 (3, BPBM R3600); Sta. D1R1, 2117ʹ23.4ʺ N, 15755ʹ30.1ʺ W, 48.8 m, Aug. 2000 (1); Sta. D2R2, 2116ʹ56.5ʺ N, 15754ʹ35.0ʺ W, 53.3 m, Aug. 2002 (1); Mamala Bay, Barbers Point outfall, Sta. HB1R5, 2116ʹ51.0ʺ N, 15759ʹ20.2ʺ W, 64.9 m, Mar. 2000 (1); Sta. HZR4, 2116ʹ53.1ʺ N, 15801ʹ30.3ʺ W, 62.5 m, Mar. 2000 (1); Sta. HB2R4, 2117ʹ0 0.5ʺ N, 15801ʹ21.2ʺ W, 59.1 m, Mar. 2000 (1); Sta. HB6R1, 2116ʹ33.1ʺ N, 15801ʹ48.1ʺ W, 59.4 m, Mar. 2000 (2); Sta. HB2R1, 2117ʹ0 0.5ʺ N, 15801ʹ21.1ʺ W, 58.8 m, Mar. 2000 (2); Sta. HB7R1, 2115ʹ30.5ʺ N, 15803ʹ11.4ʺ W, 65.2 m, Mar. 2000 (3, BPBM R3603); Sta. HB4R4, 2116ʹ47.1ʺ N, 15801ʹ38.0ʺ W, 63.4 m, Mar. 2000 (1); Sta. HB7R4, 2115ʹ30.2ʺ N, 15803ʹ11.4ʺ W, 65.2 m, Mar. 2000 (2, BPBM R3601); Sta. HB2R5, 2117ʹ0 0.4ʺ N, 15801ʹ21.5ʺ W, 59.4 m, Mar. 2001 (1); Sta. HB2R2, 2117ʹ0 0.1ʺ N, 15801ʹ21.3ʺ W, 60.0 m, Mar. 2001 (1, BPBM R3602); Sta. HB7R3, 2115ʹ30.4ʺ N, 15803ʹ11.6ʺ W, 66.4 m, Mar. 2001 (1); Sta. HZR1, 2116ʹ54.0ʺ N, 15801ʹ30.3ʺ W, 62.5 m, Mar. 2004 (1); Sta. HB2R2, 2117ʹ0 0.1ʺ N, 15801ʹ21.3ʺ W, 60.0 m, Mar. 2002 (1); Sta. HB2R1, 2117ʹ0 0.5ʺ N, 15801ʹ21.1ʺ W, 58.8 m, Mar. 2002 (1); Sta. HB6R3, 2116ʹ33.3ʺ N, 15801ʹ48.3ʺ W, 59.4 m, Feb. 2006 (1). Waianae outfall, Sta. ZWR4, 2125ʹ25.1ʺ N, 15811ʹ55.4ʺ W, 34 m, May 2001 (1); Sta. ZWR1, 2125ʹ25.1ʺ N, 15811ʹ55.4ʺ W, 34 m, May 2001 (1); Sta. W9R2, 2126ʹ29.4ʺ N, 15812ʹ16.3ʺ W, 33 m, May 2002 (1); Sta. ZR4, 2125ʹ22.9ʺ N, 15811ʹ51.1ʺ W, 35 m, May 2002 (1); Sta. W9R2, 2126ʹ29.4ʺ N, 15812ʹ16.3ʺ W, 34 m, May 2007 (1); Sta. W1R2, 2123ʹ32.5ʺ N, 15811ʹ27.7ʺ W, 31 m, Jun. 2011 (1). Maui Island: Kahekili Beach Park, collected on Halimeda kanaloana meadows, 30 m, Jun. 2005, coll. A. Fukunaga (1).

Description. Complete specimens 7–35 mm long, 0.1–0.5 mm wide for 74–180 chaetigers. Body elongate, slender, tapering from abdominal segments to pygidium; rounded in cross section. Color in alcohol pale yellow with both annuli of chaetiger 11 and anterior annulus of chaetiger 12 covered by glands staining dark brown and forming complete rings ( Fig. 15 C, D).

Prostomium conical with digitate palpode ( Figs 13 A, 14A); sometimes partially retracted. Nuchal organs not observed. Eyespots 10–14 on either side, in two irregular rows ( Fig. 13 A). Everted proboscis with papillae on distal end ( Figs 13 A, 14A). Peristomium achaetous; as long as chaetiger 1 ( Figs 13 A, 14A).

Thorax with 11 chaetigers; chaetiger 1 with notochaetae only and parapodia reduced throughout ( Figs 13 , 14 A). Chaetigers 1–4 slightly inflated dorsally, indistinctly differentiated, chaetigers 5–11 biannulated with deep inter-segmental groove ( Figs 13 A, 14A). Thorax with bilimbate capillaries only, inserted in mid-segment. Lateral organs present on thorax from chaetiger 7–11, not observed on abdominal segments. Genital pores not observed.

Transition between thorax and abdomen marked by dark brown glandular bands and change in chaetae ( Figs 13 A, 15C, D); abdominal chaetigers with hooded hooks throughout. Abdominal noto- and neuropodial hooks more closely spaced than in thoracic fascicles. Abdominal neuropodial lobes not fused ventrally, anterior abdominal segments with 10–12 hooded hooks and posteriorly with 12–14 slightly shorter hooded hooks per fascicle. Notopodial abdominal hooks slightly longer than neuropodial hooks but similar in shape. Hoods short with insertion above widest part of hook’s shoulder ( Fig. 14 D, E). Hooks with multiple teeth, in lateral view with 4–5 teeth above main fang and in frontal view with at least three rows of teeth; two in basal row, three in middle and two in superior row ( Fig. 14 D–F).

Branchiae retractile, occurring dorsally on far posterior abdominal segments, starting about 20–30 chaetigers before pygidium in large specimens ( Figs 13 B, C, 14B). Branchial tufts of 2–3 digitate lobes at each side, projecting from lateral end of notopodial lobe ( Fig 13 B, C). Pygidium with four digitate lobes, two dorsal and two ventral ( Figs 13 C, 14C); ventral lobes 1.5 longer than dorsal lobes; terminal anal aperture.

Methyl green staining pattern. Prostomium, peristomium and first 3–4 chaetigers unstained or with very light staining; staining gradually darkens from chaetiger 5 posteriorly to end of thorax ( Fig. 15 A). Abdominal chaetigers, except chaetiger 12, which stains similarly to the last thoracic chaetiger, with pre- and post-chaetal dark bands on noto- and neuropodial tori ( Fig. 15 B).

Distribution. This species was originally described from the southwest coast of Madagascar ( Thomassin 1970) but has been recorded from the Andaman Sea, Thailand ( Green 2002) and it is now newly recorded for Oahu, Hawaii. This species seems to be one of the most abundant and widely distributed capitellids in Oahu and has been erroneously identified as Notomastus tenuis in unpublished reports (see e.g. Ambrose et al. 2010).

Remarks. The specimens from Oahu, Hawaii agree well with earlier descriptions of Capitellethus cinctus by Thomassin (1970) and Green (2002). The dark pigmented bands on the transition between thorax and abdomen are conspicuous in this species and separate it readily from other Hawaiian capitellids. The MGSP for this species was well described by Green (2002) and agrees with the Hawaiian material except that chaetiger 6 is not always darkly stained and the abdominal neuropodial tori are always stained in the Hawaiian material.

The original and subsequent descriptions of this species were based on fragmented specimens and the far posterior abdominal segments and pygidium had not been previously described. Branchial tufts are present on posterior segments and are illustrated herein in line drawings and SEM images. The pygidium is very distinct with four digitate lobes; the anal aperture is terminal.

Capitellethus cinctus is distinct from its congeners due to the presence of only capillaries in thoracic chaetigers, chaetiger 1 being uniramous, darkly pigmented glandular bands on chaetigers 11–12, the presence of branchiae, and a distinct MGSP. It is most similar to Capitellethus branchiferus Gallardo, 1968 but as pointed out by Green (2002), these species have a distinct MGSP and C. branchiferus has hooded hooks in the neuropodium of chaetiger 11.

Figures

FIGURE 13. Capitellethus cinctus: A, anterior end in lateral view; B, posterior abdominal segments with paired tufts of branchiae in dorsal view; C, posterior end with pygidium in lateral view showing anal cirri.

FIGURE 14. SEM of Capitellethus cinctus: A, anterior end in lateral view; B, posterior abdominal segments in ventral view with paired tufts of branchiae in dorsum; C, posterior end with pygidium and anal cirri; D, abdominal hooded hooks; E, hooded hook in lateral view; F, hook with hood removed in frontal view showing multiple rows of spines.

FIGURE 15. Capitellethus cinctus: A, MGSP of anterior end; B, MGSP of abdominal region; C – D, brownish glandular belts between thorax and abdomen on preserved specimens. Heteromastus cf. filiformis: E, MGSP of anterior region including thorax and beginning of abdomen; F, MGSP of posterior abdominal segments.