Capitella minima Langerhans, 1881

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 : 11-13

Capitella minima Langerhans, 1881

Figures 6 B, 7 A–E, 8 A–F

Capitella minima Langerhans, 1881: 99 .

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

Material examined. Oahu Island: Mamala Bay, Sand Island outfall, Sta. C2AR3, 21°17ʹ21.9ʺ N, 157° 54ʹ 36.6ʺ W, 18.6 m, Aug. 2000 (4, BPBM R3590); Sta. E2R3, 21°16ʹ42.8ʺ N, 157°54ʹ38.9ʺ W, 101.5 m, Aug. 2001 (1, BPBM R3591); Mamala Bay, Barbers Point outfall, Sta. HB4R3, 21°16ʹ46.9ʺ N, 158°01ʹ38.2ʺ W, 63.4 m, Feb. 2006 (2, BPBM R3592); Sta. HB4R1, 21°16ʹ46.9ʺ N, 158°01ʹ38.1ʺ W, 63.7 m, Feb. 2006 (5, BPBM R3593); Sta. HB6R4, 21°16ʹ33.1ʺ N, 158°01ʹ48.2ʺ W, 59.4 m, Mar. 2002 (3); Sta. HB6R2, 21°16ʹ33.5ʺ N, 158°01ʹ48.2ʺ W, 59. 7 m, Mar. 2002 (4); Sta. HB3R1, 21°16ʹ50.6ʺ N, 158°01ʹ28.7ʺ W, 77.7 m, Mar. 2000 (1); Sta. HZR5, 21°16ʹ53.7ʺN, 158°01ʹ29.7ʺ W, 62.8 m, Mar. 2003 (1); Sta. HB4R5, 21°16ʹ47.0ʺ N, 158°01ʹ38.0ʺ W, 63.1 m, Mar. 2000 (2); Sta. HB4R3, 21°16ʹ46.9ʺ N, 158°01ʹ38.2ʺ W, 63.4 m, Mar. 2001 (2, BPBM R3594); Sta. HB4R4, 21°16ʹ47.1ʺ N, 158°01ʹ38.0ʺ W, 63.4 m, Mar. 2001 (9, BPBM R3595); Sta. HZR4, 21°16ʹ53.1ʺ N, 158°01ʹ30.3ʺ W, 62.5 m, Mar. 2002 (2, BPBM R3596); Sta. HB4R2, 21°16ʹ47.1ʺ N, 158°01ʹ38.3ʺ W, 63.4 m, Mar. 2002 (3, BPBM R3597); Sta. HZR2, 21°16ʹ53.3ʺ N, 158°01ʹ30.6ʺ W, 62.8 m, Mar. 2000 (1); Sta. HB4R3, 21°16ʹ46.9ʺ N, 158°01ʹ38.2ʺ W, 63. 4 m, Mar. 2000 (1); Sta. HB3R4, 21°16ʹ52.0ʺ N, 158°01ʹ30.5ʺ W, 68.0 m, Mar. 2000 (1); Sta. HB2R1, 21°17ʹ0 0.5ʺ N, 158°01ʹ21.1ʺ W, 58.8 m, Mar. 2000 (1); Sta. HB4R5, 21°16ʹ47.0ʺ N, 158°01ʹ38.0ʺ W, 63.1 m, Mar. 2000 (6, 4 on SEM stub); Sta. HB3R2, 21°16ʹ53.2ʺ N, 158°01ʹ29.8ʺ W, 67.1 m, Mar. 2002 (1); Sta. HB3R5, 21°16ʹ52.6ʺ N, 158°01ʹ29.8ʺ W, 68.0 m, Mar. 2002 (1); Sta. HB3R3, 21°16ʹ52.6ʺ N, 158°01ʹ29.9ʺ W, 67.1 m, Mar. 2002 (1); Sta. HB3R3, 21°16ʹ52.6ʺ N, 158°01ʹ29.9ʺ W, 67.1 m, Mar. 2001 (2); Sta. HB4R3, 21°16ʹ46.9ʺ N, 158°01ʹ38.2ʺ W, 63. 4 m, Jan. 2009 (3); Waianae outfall, Sta. ZWR6, 21°25ʹ25.1ʺ N, 158°11ʹ55.4ʺ W, 34 m, May 2002 (2); Sta. W2R1, 21°24ʹ46.5ʺ N, 158°11ʹ45.6ʺ W, 27.4 m, May 2000 (1); Sta. ZWR5, 21°25ʹ25.1ʺ N, 158°11ʹ55.4ʺ W, 34 m, May 2001 (1); Kailua Bay, Mokapu outfall, Sta. CR4, 21°26ʹ58.3ʺ N, 157°42ʹ54.9ʺ 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 A–D, 8A, C); nuchal organs and eyespots not observed. Peristomium distinct from prostomium forming complete ring; dorsally elevated and twice longer dorsally than ventrally ( Figs 7 A, 8C). 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 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 A–D, 8A, 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 A, B, 8A, 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 B, 8B).

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 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 E, 8E).

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 B); chaetigers 8–9 and sometimes anterior 2–3 abdominal segments with green speckles ( Fig. 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.

Figures

FIGURE 6. Capitella jonesi: A, MGSP of anterior end in lateral view. Capitella minima: B, MGSP of anterior end in lateral view. Capitella sp.: C, MGSP of female individual; D, MGSP of male individual. Capitella teleta: E, MGSP of female individual; F, MGSP of male individual.

FIGURE 7. Capitella minima: A, male individual in lateral view; B, male individual in dorsal view showing genital hooks; C, female individual in lateral view; D, female individual in dorsal view; E, posterior end with pygidium.

FIGURE 8. SEM of Capitella minima: A, anterior end of female individual in lateral view; B, anterior end of male individual in dorsal view showing genital spines; C, anterior end in lateral view showing delimitations between prostomium, peristomium and chaetiger 1; D, thoracic capillaries; E, posterior end with pygidium; F, abdominal hooded hooks.