Pycnoderma congoense Grube, 1877

Salazar-Vallejo, Sergio I., 2011, Revision of Piromis Kinberg, 1867 and Pycnoderma Grube, 1877 (Polychaeta: Flabelligeridae), Zootaxa 2819, pp. 1-50 : 31-33

Pycnoderma congoense Grube, 1877

Figure 13

Pycnoderma congoense Grube, 1877b:540 –541; Augener, 1918:451 –452, Pl. 6, Fig. 147, Text fig. 58 (redescr.); Monro, 1930:162 –163, Fig 65; Day, 1967:656, Figs. 32.1g –l; Intes & leLoeuff, 1977:235; Hartwich, 1993:91.

Piromis congoense: Kirkegaard, 1996:64 .

Diplocirrus longisetosus: Rullier, 1964:1094 (non von Marenzeller, 1890).

Stylarioides congoense Kirkegaard, 1959:39 –40 (partim).

Stylarioides scutigeroides: Rullier, 1965:48 (non Augener, 1918).

Type material. Tropical Eastern Atlantic Ocean. Three syntypes (ZMB-856, ZMB-869, ZMB-Q4754), off Congo, R/V Gazelle, no further data (longest used for redescription; 869: anterior fragment, anteroventrally dissected, most chaetae broken, papillae eroded, breaking in two pieces, 91 mm long, 3.5 mm wide, cephalic cage 3 mm long, 92 chaetigers; thicker neurospines from chaetiger 12; 4754: anterior fragment, not dissected, most chaetae broken, papillae not eroded, 60 mm long, 3 mm wide, cephalic cage 4 mm long, 70 chaetigers; thicker neurospines from chaetiger 10, four neurochaetae by chaetiger 14).

Additional material. Tropical Eastern Atlantic Ocean. One slide (IRFA-W58) of D. longisetosus (from Rullier 1965, with several parapodia; resin collapsed but chaetae still visible). One specimen ( IRFA), off Point-Noire, Congo (04°51ʹ S, 11°43ʹ E), 50 m, 12 Aug. 1963, A. Crosnier, coll. (fixed in alcohol, anterior fragment, previously dissected). One specimen ( IRFA /2), off Point-Noire, Congo, 35–40 m, 30 Oct. 1963, A. Crosnier, coll. (complete). One specimen (MNHN-507a), WSW off Bibundi, Cameroun, Sta. 112 (04°08ʹ30ʺ N, 08°52ʹ35ʺ E), 25 m, Dec. 1962, A. Crosnier, coll. (id. as D. longisetosus ; partly dehydrated specimen, complete, damaged; most cephalic cage and body chaetae lost. Neurospines from chaetiger 5). One specimen (MNHN-507b) breaking into three parts, many neurochaetae broken off, off Benin, St. 3, 48 m, gray sand, 8 Oct. 1963, A. Crosnier, coll. (id. as S. scutigeroides ). One specimen (ZMUC-1797), off Nigeria, R/V Atlantide, Sta. 103 (04°38ʹ N, 05°19ʹ E), 40 m, 17 Feb. 1946 (anterior fragment; first neurospines in chaetiger 10). One specimen (ZMUC-1798), off Lobito, Angola, R/V Galathea, Sta. 124 (12°20ʹ S, 13°40ʹ E), 45 m, 20 Dec. 1950 (anterior fragment; first neurospines in chaetiger 12). One specimen (ZMUC-1799), off Lobito, Angola, R/V Galathea, Sta. 125 (12°20ʹ S, 13°40ʹ E), 60 m, 20 Dec. 1950 (anterior fragment; first neurospines in chaetiger 12).

Description. Largest syntype (ZMB-856) pale brown; anterior fragment, slightly damaged, anteriorly collapsed, breaking into four fragments. Body cylindrical, anteriorly swollen, tapering medially and posteriorly ( Fig. 13 A); tunic papillated, first few chaetigers with tough cuticle, papillae eroded; with fine adhering sediment particles, barely visible, giving body a naked dorsal surface ( Fig. 13 B, D), as well as laterally ( Fig. 13 C); papillae minute, clavate, abundant, but most eroded, slightly longer on chaetal lobes. Syntype 100 mm long, 2.5 mm wide, cephalic cage 3 mm long (neurochaetae; notochaetae lost), 83 chaetigers.

Anterior end not exposed, observed in an already dissected syntype (ZMB-869). Cephalic hood tube short; margin finely papillated. Prostomium low; with four small, dark eyes (confirmed in IRFA specimens, Fig. 13 E). Caruncle extending to branchial plate margin, wider basally, tapering distally, slightly elevated. Palps pale, corrugated; palp keels triangular, small. Lips damaged during dissection. Branchiae all thin, cirriform, maculated, arising on a tongue-like protuberance; filaments arranged in two lateral groups, each with filaments in rows, of about 100 filaments. Most branchial filaments of similar length, about as long as palps. Nephridial lobes not seen.

Cephalic cage chaetae slightly longer than body width; only chaetiger 1 involved in the cephalic cage, following chaetigers with elongate chaetae but shorter than those present in chaetiger 1. Cephalic cage chaetae arranged in short dorsolateral row, noto- and neurochaetae close to each other; each with four chaetae per bundle.

Anterior dorsal margin of chaetiger 1 smooth. Anterior chaetigers without especially long papillae. Chaetigers 1–3 of similar length, wider than long. Chaetal transition from cephalic cage to body chaetae gradual, thicker neurospines with long articles completely replace capillaries by chaetiger 16. Gonopodial lobes not seen.

Parapodia lateral, poorly developed, with chaetae emerging from the body wall; anterior 4–5 parapodia forming short, petaloid, anteriorly directed lobe. Medial neuropodia ventrolateral. Noto- and neuropodia each with a row of 4–6 clavate, elongate postchaetal papillae, diminishing in size posteriorly.

Median notochaetae arranged in short transverse row, 8–10 per fascicle, as long as 1/3 body width; posterior notochaetae darker, thicker; all notochaetae multiarticulated capillaries with short articles basally, slightly longer medially and distally ( Fig. 13 F); neurochaetae multiarticulated capillaries, gradually replaced by aristate neurospines from chaetiger 10; by chaetiger 16 only aristate neurospines ( Fig. 13 G); arranged in a short transverse row, 6–7 per fascicle. Following chaetigers with aristate neurospines, with progressively fewer, longer articles ( Fig. 13 H), then articles reduced in number ( Fig. 13 I, J), and a single, short article present before distal, multiarticulate, dehiscent arista. Each aristate neurospine darker basally and medially, less pigmented distally.

Posterior end unknown.

Variation. The anterior chaetigers are darker or redder than the remainder of the body. This pigmentation is probably due to the adhered sediment particles since it is restricted to the outer tunic layer.

Remarks. Pycnoderma congoense Grube, 1877 , resembles P. dannyi n. sp. (see below) by having a transparent, sediment-free tunic; the two species differ markedly, however, in the relative length of anterior chaetigers and in the relative abundance of papillae over the whole body. In P. congoense , anterior chaetigers are short and the body has 6–8 rows of small, delicate papillae, while in P. dannyi n. sp., the anterior chaetigers are longer with about three rows of larger papillae.

Distribution. Originally described from Congo, the species ranges along tropical Western Africa, in shallow water (20–60 m).

Figures

FIGURE 13. Pycnoderma congoense Grube, 1877. A. Syntype (ZMB 869), without posterior end, dorsal view; insert: anterior end, dorsal view. B. Syntype (ZMB 856), anterior end, dorsal view. C. Syntype (ZMB 4754), anterior end, lateral view. D. Nontype specimen (IRFA unnumb.), anterior end, dorsal view. E. Same, head exposed, slightly eroded, branchiae and palps removed (BS: branchial scars, Ca: caruncle, Pr: Prostomium, PS: palp scar). F. Syntype (ZMB 4754), parapodium from chaetiger 4. G. Same, neurochaetae from chaetiger 14. H. Syntype (ZMB 856), neurochaetae from chaetiger 37 (insert: chaetal tips). I. Syntype (ZMB 4754), neurochaetae from chaetiger 57. J. Non-type specimen (IRFA), neurochaetae from chaetiger 86 (insert: chaetal tips after pressing the cover slip). Scale bars: A: 5 mm, B – D: 1 mm, E: 0.5 mm, F: 300 µm, G: 225 µm, H: 90 µm, I: 180 µm, J: 75 µm.