Exogone rolani

Paresque, Karla, Fukuda, Marcelo Veronesi & Nogueira, João Miguel De Matos, 2014, The genus Exogone (Polychaeta: Syllidae) from the Brazilian coast, with the description of a new species, Zootaxa 3790 (4), pp. 501-533 : 514-517

Exogone rolani San Martín, 1991

( Figures 7–8 )

Exogone rolani San Martín, 1991: 731 –733, fig. 9.

Material examined. Project ‘ HABITATS’: All collections off the state of Rio de Janeiro (Campos Basin), Van Veen grab; 21°21'21"S 40°52'9"W, 20 m: 1 specimen, coll. 23 July 2009; 21°22'58"S 40°19'41"W, 52 m: 18 specimens, coll. 0 5 March 2009; 9 specimens, coll. 21 July 2009; 21°28'2"S 40°56'22"W, 15 m: 3 specimens, coll. 20 July 2009; 22°3'45"S 40°9'59"W, 75 m: 2 specimens, coll. 25 February 2009; 22°4'14"S 40°6'59"W, 91 m: 1 specimen, coll. 25 February 2009. Project ‘ BioPol-NE ’: State of Paraíba: Baía da Traição, Praia do Farol (06º41'S 34º55'W), intertidal: 6 specimens, coll. 0 9 August 2010. Rio Tinto, Barra de Mamanguape (06º45'S 34º55'W), intertidal: 2 specimens, coll. 0 2 February 2010. João Pessoa, Cabo Branco (07o08'S 34o47'W), intertidal: 1 specimen ( MZUSP 2078), coll. 0 2 February 2010. State of Pernambuco, Ilha de Itamaracá, Recifes de Itamaracá, (07°43.944'S 34°49.200'W), 1 m: 25 specimens ( MZUSP 2080), coll. 15 December 2012.

Description. Body thin, elongated, longest specimens ca. 5.6 mm long and 0.17 mm wide, with up to 32 chaetigers. Palps triangular, distally rounded, almost totally fused, with conspicuous line of fusion and distal notch ( Fig. 7 A). Prostomium pentagonal, slightly shorter than palps ( Figs 7 A, 8A), with two pairs of eyes in trapezoidal arrangement, eyespots absent; antennae in transverse row, inserted close to each other; median antenna inserted between anterior pair of eyes, elongated, reaching beyond tip of palps, abruptly tapering distally ( Fig. 7 A); lateral antennae ovate ( Figs 7 A, 8A). Ciliated nuchal organs dorsolaterally between prostomium and peristomium, close to peristomial cirri, visible only under SEM ( Fig. 8 A–C). Peristomium shorter than following chaetigers, sometimes covering posterior part of prostomium, including posterior pair of eyes; peristomial cirri similar to lateral antennae but smaller ( Fig. 7 A). Dorsal cirri ovate, slightly larger than peristomial cirri, present on all chaetigers ( Fig. 7 A, 8B).Ventral cirri similar to dorsal cirri but smaller, about 2/3 as long as parapodial lobes ( Fig. 8 K). Parapodial lobes conical; anterior parapodia with 1–2 spiniger-like chaetae and 8–10 falcigers each ( Fig. 8 F), midbody parapodia with single spiniger-like chaeta and three falcigers each ( Fig. 8 K), posterior parapodia with single spiniger-like chaeta and two falcigers each; shafts of spiniger-like chaetae subdistally spinulated; blades of spiniger-like chaetae unidentate, with fine marginal spines, spines close to base of blade longer, diminishing in length towards tip; blades 25–12 µm long on anterior body, 25–15 µm on midbody, and 12–8 µm on posterior body ( Figs 7 D, H, M, 8D); shafts of falcigers on chaetigers 1–5 modified, with large, pointed, oblique tip, reaching half length of blades ( Figs 7 E, 8F–H); from chaetiger 6 onwards shafts subdistally inflated, spinulated, with acute tip ( Figs 7 I, N, 8I –L); blades of falcigers on chaetigers 1–5 bidentate, subdistal tooth long, pronounced, about as long as blade, distal tooth thin, shorter, spinulation on cutting edge inconspicuous ( Figs 7 E, 8F–H); from chaetiger 6 onwards blades spinulated, subdistal tooth distinctly shorter than on anteriormost chaetigers, but longer than distal tooth ( Figs 7 I, N, 8I –K); blades 10–9 µm long on anterior body, ca. 7 mm long on midbody and 5 mm long on posterior body. Dorsal simple chaetae present on all chaetigers, subdistally spinulated, with rounded tip on anterior body ( Figs 7 C, 8I), progressively thicker, more conspicuously sigmoid and with acute tip towards posterior body ( Figs 7 G, K, 8L); ventral simple chaetae present only on posterior chaetigers, sigmoid, bidentate, with subdistal tooth larger than distal tooth ( Fig. 7 L). Anterior parapodia with up to two aciculae each, one straight, with acute tip, another slightly bent subdistally, with inflated, rounded tip ( Fig. 7 B); midbody and posterior chaetigers with single acicula each, of the second type, stouter posteriorwards ( Fig. 7 F, J). Pygidium with thin, elongate pair of anal cirri ( Fig. 8 M). Pharynx through 3.5–5 segments; tooth set slightly back from anterior border ( Fig. 7 A); anterior margin of pharynx smooth, without papillae, surrounded by fringe of cilia ( Fig. 8 E); proventricle extending for 5–7 chaetigers, with ca. 29 rows of muscle-cells.

Remarks. Exogone rolani was described based on specimens from Cuba and it is characterized by having a median antenna longer than the lateral ones and longer than the prostomium and peristomium together, dorsal cirri present on all chaetigers, shafts of spiniger-like chaetae of chaetigers 1 and 2 without a triangular process, and falcigers of anteriormost chaetigers with a subdistal tooth distinctly longer than in the remaining species of this genus. This latter character is found only in E. rolani and it is the most diagnostic feature to distinguish this species from the remaining species in this genus.

Exogone arenosa , E. dispar , E. gigas sp. n. and E. lourei are the other species of Exogone with a median antenna longer than the lateral ones that occur off the Brazilian coast. All these species differ from E. rolani by having bidentate blades of falcigers with a subdistal tooth that is not remarkably longer than the distal one, even on anteriormost chaetigers. Moreover, E. arenosa , E. gigas sp. n., and E. lourei have a triangular process on the shafts of the spiniger-like chaetae of chaetiger 2 which is absent in E. rolani .

Brazilian specimens match the description based on Cuban material ( San Martín 1991), except for having longer palps and a longer proventricle, the latter extending through 5–7 chaetigers, with 27–29 rows of muscle cells, while Cuban specimens have a proventricle extending for 3–5 segments, with up to 25 muscle-cell rows.

Type locality. Cuba, Archipelago de los Canarreos (Atlantic Ocean).

Distribution. Atlantic Ocean: USA (East coast), Cuba, Brazil (Paraíba, Rio de Janeiro). From the intertidal zone to ca. 91 m deep.

Figures

FIGURE 7. Exogone rolani. (A) Anterior body, dorsal view; (B) acicula, anterior body; (C) dorsal simple chaeta, anterior body; (D) spiniger-like chaetae, anterior body; (E) falcigers, chaetigers 1 – 5; (F) acicula, midbody; (G) dorsal simple chaeta, midbody; (H) spiniger-like chaeta, midbody; (I) falcigers, midbody; (J) acicula, posterior body; (K) dorsal simple chaeta, posterior body; (L) ventral simple chaeta, posterior body; (M) spiniger-like chaeta, posterior body; (N) falcigers, posterior body. Scale bars: A, 200 µm; B – N, 10 Μm.

FIGURE 8. Exogone rolani, SEM. (A) (B) Anterior end, dorsal view; (C) detail of nuchal organ; (D) spiniger-like chaeta, chaetiger 2; (E) pharynx opening, frontal view; (F) chaetae, chaetiger 2; (G) falciger, chaetiger 3; (H) falcigers, chaetiger 3; (I) chaetae, chaetiger 6; (J) ventral-most falciger, midbody; (K) chaetae, midbody; (L) chaetae, posterior body parapodium; (M) posterior end, frontal view. Arrows point to nuchal organ. Scale bars: A – B, 50 Μm; C, E – F, I, L, 10 Μm; D, J, 5 Μm; G – H, 2 Μm; K, M, 20 Μm.