Capitella minima Langerhans, 1881

Capitella minima Langerhans, 1881

Figures 6 View FIGURE 6 B, 7 A–E, 8 A–F

Capitella minima Langerhans, 1881: 99 .

Capitella minima .— Green 2002: 261 –263, fig. 4 a–f. Capitomastus minimus .— Eisig 1887: 857 –859. Capitella minimus .- Warren 1991: 280.

Material examined. Oahu Island: Mamala Bay, Sand Island outfall, Sta. C 2 AR3, 21° 17 ʹ 21.9 ʺ N, 157 ° 54 ʹ 36.6 ʺ W, 18.6 m, Aug. 2000 (4, BPBM R 3590); Sta. E 2 R3, 21° 16 ʹ 42.8 ʺ N, 157 ° 54 ʹ 38.9 ʺ W, 101.5 m, Aug. 2001 (1, BPBM R 3591); Mamala Bay, Barbers Point outfall, Sta. HB 4 R3, 21° 16 ʹ 46.9 ʺ N, 158 °01ʹ 38.2 ʺ W, 63.4 m, Feb. 2006 (2, BPBM R 3592); Sta. HB 4 R1, 21° 16 ʹ 46.9 ʺ N, 158 °01ʹ 38.1 ʺ W, 63.7 m, Feb. 2006 (5, BPBM R 3593); Sta. HB 6 R4, 21° 16 ʹ 33.1 ʺ N, 158 °01ʹ 48.2 ʺ W, 59.4 m, Mar. 2002 (3); Sta. HB 6 R2, 21° 16 ʹ 33.5 ʺ N, 158 °01ʹ 48.2 ʺ W, 59. 7 m, Mar. 2002 (4); Sta. HB 3 R1, 21° 16 ʹ 50.6 ʺ N, 158 °01ʹ 28.7 ʺ W, 77.7 m, Mar. 2000 (1); Sta. HZR5, 21° 16 ʹ 53.7 ʺN, 158 °01ʹ 29.7 ʺ W, 62.8 m, Mar. 2003 (1); Sta. HB 4 R5, 21° 16 ʹ47.0ʺ N, 158 °01ʹ38.0ʺ W, 63.1 m, Mar. 2000 (2); Sta. HB 4 R3, 21° 16 ʹ 46.9 ʺ N, 158 °01ʹ 38.2 ʺ W, 63.4 m, Mar. 2001 (2, BPBM R 3594); Sta. HB 4 R4, 21° 16 ʹ 47.1 ʺ N, 158 °01ʹ38.0ʺ W, 63.4 m, Mar. 2001 (9, BPBM R 3595); Sta. HZR4, 21° 16 ʹ 53.1 ʺ N, 158 °01ʹ 30.3 ʺ W, 62.5 m, Mar. 2002 (2, BPBM R 3596); Sta. HB 4 R2, 21° 16 ʹ 47.1 ʺ N, 158 °01ʹ 38.3 ʺ W, 63.4 m, Mar. 2002 (3, BPBM R 3597); Sta. HZR2, 21° 16 ʹ 53.3 ʺ N, 158 °01ʹ 30.6 ʺ W, 62.8 m, Mar. 2000 (1); Sta. HB 4 R3, 21° 16 ʹ 46.9 ʺ N, 158 °01ʹ 38.2 ʺ W, 63. 4 m, Mar. 2000 (1); Sta. HB 3 R4, 21° 16 ʹ52.0ʺ N, 158 °01ʹ 30.5 ʺ W, 68.0 m, Mar. 2000 (1); Sta. HB 2 R1, 21° 17 ʹ0 0.5 ʺ N, 158 °01ʹ 21.1 ʺ W, 58.8 m, Mar. 2000 (1); Sta. HB 4 R5, 21° 16 ʹ47.0ʺ N, 158 °01ʹ38.0ʺ W, 63.1 m, Mar. 2000 (6, 4 on SEM stub); Sta. HB 3 R2, 21° 16 ʹ 53.2 ʺ N, 158 °01ʹ 29.8 ʺ W, 67.1 m, Mar. 2002 (1); Sta. HB 3 R5, 21° 16 ʹ 52.6 ʺ N, 158 °01ʹ 29.8 ʺ W, 68.0 m, Mar. 2002 (1); Sta. HB 3 R3, 21° 16 ʹ 52.6 ʺ N, 158 °01ʹ 29.9 ʺ W, 67.1 m, Mar. 2002 (1); Sta. HB 3 R3, 21° 16 ʹ 52.6 ʺ N, 158 °01ʹ 29.9 ʺ W, 67.1 m, Mar. 2001 (2); Sta. HB 4 R3, 21° 16 ʹ 46.9 ʺ N, 158 °01ʹ 38.2 ʺ W, 63. 4 m, Jan. 2009 (3); Waianae outfall, Sta. ZWR6, 21° 25 ʹ 25.1 ʺ N, 158 ° 11 ʹ 55.4 ʺ W, 34 m, May 2002 (2); Sta. W 2 R1, 21° 24 ʹ 46.5 ʺ N, 158 ° 11 ʹ 45.6 ʺ W, 27.4 m, May 2000 (1); Sta. ZWR5, 21° 25 ʹ 25.1 ʺ N, 158 ° 11 ʹ 55.4 ʺ W, 34 m, May 2001 (1); Kailua Bay, Mokapu outfall, Sta. CR4, 21° 26 ʹ 58.3 ʺ N, 157 ° 42 ʹ 54.9 ʺ W, Aug. 1992 (2); Mamala Bay, Sta. 1, Aug. 2001 (9); Sta. 30, Aug. 2001 (3).

Description. Complete specimens 2–7 mm long, 0.1–0.15 mm wide for about 28–45 chaetigers. Body elongate, wider on mid-thoracic chaetigers, gradually narrowing posteriorly; ventral groove beginning after chaetiger 6–7; groove deeper on abdominal segments. Color in alcohol white to pale yellow.

Prostomium triangular, rounded anteriorly, shorter or subequal in length to peristomium ( Figs 7 View FIGURE 7 A–D, 8 A, C); nuchal organs and eyespots not observed. Peristomium distinct from prostomium forming complete ring; dorsally elevated and twice longer dorsally than ventrally ( Figs 7 View FIGURE 7 A, 8 C). Proboscis not observed.

Thorax with nine chaetigers. Chaetal arrangement of thoracic chaetigers consistent throughout size range analyzed. Chaetigers 1–4 with four unilimbate capillaries per fascicle ( Fig. 8 View FIGURE 8 D); chaetigers 5–7 with 5–6 hooded hooks per fascicle; females with chaetigers 8–9 having 5–6 hooded hooks and males with chaetigers 8–9 having notopodial spines and neuropodial hooks ( Figs 7 View FIGURE 7 A–D, 8 A, B). Thoracic segments not distinctly biannulate, wider than long; constriction present after chaetiger 4 and 7 and chaetigers 5–7 enlarged in comparison to adjacent thoracic segments ( Figs 7 View FIGURE 7 A, B, 8 A, B). Genital spines present on chaetigers 8–9 of males; chaetiger 8 with two sets of 1–2 spines each facing posteriorly and chaetiger 9 with 2 enlarged spines facing anteriorly ( Figs 7 View FIGURE 7 B, 8 B).

Abdominal segments multi–annulated, almost as long as wide, with hooded hooks throughout. Abdominal hooks similar to thoracics; anteriorly with 5–6 hooded hooks, reduced posteriorly to 2–3 hooks ( Fig. 8 View FIGURE 8 F). Noto- and neuropodia well separated, glandular tori pads poorly developed. Lateral organs and genital pores not observed. Hooded hooks with slightly inflated nodes, main fang extending slightly beyond hoods. Hooks with moderate anterior shaft and two rows of teeth—three in basal row and 2–3 in superior row.

Pygidium an oval lobe with terminal anus ( Figs 7 View FIGURE 7 E, 8 E).

Methyl green staining pattern. Males and females with similar staining pattern. Entire body stains with a solid light green. Prostomium, peristomium and first four chaetigers with sparse green speckles. Chaetigers 5–7 with green speckles concentrated on posterior edge of each segment ( Fig. 6 View FIGURE 6 B); chaetigers 8–9 and sometimes anterior 2–3 abdominal segments with green speckles ( Fig. 6 View FIGURE 6 B); females with larger abdominal stained area than males. Mid- to posterior abdomen lacking distinct MGSP, some specimens with green speckles on the posterior edge of segments.

Distribution. Capitella minima is widely distributed in the Atlantic, Mediterranean Sea, Indian Ocean, and Andaman Sea ( Green 2002). The record in Hawaii of a Capitella species with four thoracic chaetigers with capillaries only is new to the western Pacific Ocean.

Remarks. The specimens described herein fit well the description of Capitella minima by Green (2002). Several Capitella species have capillary chaetae restricted to chaetigers 1–4: Capitella minima , Capitella minima tulearensis ( Thomassin, 1970) , Capitella capitata floridana Hartman, 1959 and Capitella hermaphrodita Boletzky & Dohle, 1967 . However, C. minima is distinct from these similar species in having normal capillaries in chaetiger 1 (not an acicular-type as in C. m. tulearensis ), separate sexes with only males having genital spines, genital spines few in number, peristomium forming a complete ring, distinct MGSP and occurrence in soft sediments rather than restricted to squid egg masses.

Biology. Specimens with fecal pellets adhered to external body wall; no tube observed. Eggs 30–35 µm in diameter.