Heteromastus cf. filiformis ( Claparède, 1864 ), Claparede, 1864

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 : 24-25

Heteromastus cf. filiformis ( Claparède, 1864)

Figures 15 E–F, 16 A–C, 17 A–F

Capitella filiformis Claparède, 1864: 49 –50, pl. 4, fig. 10. Eisig 1887: 839, 841–843. Heteromastus filiformis .— Hutchings & Rainer 1981 (and references therein, including a list of synonymous species): 373–380. Blake 2000: 69 –70, fig. 4.8a–g.

Material examined. Oahu Island: Maunalua Bay, among branches of the invasive green alga Avrainvillea amadelpha , intertidal depths, 21°16ʹ49.4ʺ N, 157°43ʹ48.5ʺ W, coll. W. Magalhães & B. Dugan, Mar. 2010: Sta. A1R3 (1), Sta. A4R2 (2, BPBM R3622; 2 on SEM stub); Sta. A7R3 (1, BPBM R3623); Sta. A4R3 (1); Sta. A10R2 (1, BPBM R3624); Sta. A6R3 (1, BPBM R3604); Sta. A8R3 (2).

Description. Complete specimen 8.5 mm long, 0.2 mm wide for 61 chaetigers. Incomplete specimens 3–18 mm long, 0.2 mm wide for 33–76 chaetigers. Body elongate, slender, widest in mid–thoracic chaetigers, tapering from abdomen to pygidium. Color in alcohol pale yellow.

Prostomium conical, small ( Figs 16 A, 17A, B); nuchal organs and eyespots not observed. Everted proboscis with numerous short papillae ( Figs 16 A, 17B). Peristomium achaetous, twice as long as anterior thoracic chaetigers ( Figs 16 A, 17A, B).

Thorax with 11 chaetigers ( Figs 16 A, 17A); thoracic segments distinctly biannulate from chaetiger 4, with shallow intra- and inter-segmental grooves; chaetigers 1–5 with 6–8 bilimbate capillaries in noto- and neuropodia; chaetigers 6–11 with 4–8 hooded hooks per fascicle ( Fig. 17 C). Notopodia in dorso-laterally and neuropodia in lateral positions ( Figs 16 A, 17A). Lateral organs present between noto- and neuropodia of thoracic chaetigers, closer to notopodia; indistinct on abdomen. Genital pores not observed.

Transition between thorax and abdomen marked by constriction and change in shape of segments ( Fig. 17 A); abdominal segments multiannulated, slightly inflated dorsally and with hooded hooks in well separated noto- and neuropodia ( Figs 16 A, 17A). Abdominal segments with posterior parapodial ridges ( Fig. 16 B). Anterior abdominal parapodia with 6–7 hooded hooks per fascicle; reduced to 1–2 hooks in far posterior segments. Abdominal hooks twice as long as thoracics. Hooks with multiple teeth, with at least three rows in frontal view; 3–4 in basal row, 4–5 in both middle and superior rows ( Fig. 17 E, F).

Branchiae not observed; abdominal notopodia slightly expanded, not forming distinct lobes ( Fig. 16 B). Pygidium with short, digitate mid-ventral caudal cirrus as long as one posterior-end segment; with terminal anal aperture ( Figs 16 C; 17D).

Methyl green staining pattern. Anterior end to chaetiger 5 staining uniformly light green with randomly distributed speckles ( Fig. 15 E). Transverse bands of speckles present from chaetiger 6 to mid-abdominal segments; a single large band present on mid segmental regions (faded after 5–6 chaetigers) and a band of speckles on posterior half of segments ( Fig. 15 F).

Distribution. Widespread in the Atlantic, Pacific and Mediterranean ( Blake 2000).

Remarks. Heteromastus filiformis is characterized by having simple branchiae and although the Hawaiian material agrees well with the description of material from California, branchiae were not found. Some specimens presented posterior notopodial lobes as small projections. MGSP also differs in the light green staining of the prostomium and peristomium compared to the lack of staining in California material; Hawaiian material also lacks mid-ventral bands. The apparent lack of branchiae may suggest that the Hawaiian material is probably younger than the specimens described in Blake (2000).

Figures

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.

FIGURE 16. Heteromastus cf. filiformis: A, anterior end in lateral view; B, abdominal segments in dorsal view; C, posterior end segments with pygidium and anal cirrus.

FIGURE 17. SEM of Heteromastus cf. filiformis: A, anterior end in lateral view; B, anterior end showing delimitations between prostomium, peristomium and chaetiger 1; C, thoracic hooded hooks; D, posterior end with pygidium in lateral view; E, abdominal hooded hooks; F, detail of abdominal hooded hook in top view.