Exogone dispar ( Webster, 1879 )

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 : 517-521

Exogone dispar ( Webster, 1879)

( Figures 9–11 )

Paedophyllax dispar Webster, 1879: 223 –224, pl. 4, fig. 49, pl. 5, figs 50–55

Exogone dispar . Westheide 1974: 298 –301, figs 48–49; Perkins 1981: 1090 –1091; Uebelacker 1984: 30 –43, fig. 30–36; Campoy 1982: 290, pl. 21; San Martín 1984: 221 –224, pl. 52.

Exogone (Exogone) dispar . San Martín 1991: 729 –730; 2003: 274–276, figs 149–150; 2005: 137–138, figs 81F, 85; Ruíz- Ramírez & Salazar-Vallejo 2001: 127, fig. 3 (45–54); Fukuda 2010: 126 –129, fig. 35.

Material examined. Project ‘ REVIZEE ’: State of Rio de Janeiro: 21º51'S 40º07'W, 110 m: 2 specimens, coll. 0 2 March 1998; 23º06'S 42º24'W, 93 m: 10 specimens, coll. 16 February 1998; 23º20'S 41º22'W, 110 m: 12 specimens, coll. 28 February 1998; 23º26'S 41º15'W, 145 m: 1 specimen, coll. 27 February 1998; 24º02'S 43º30'W, 147 m: 18 specimens, coll. 14 February 1998. State of São Paulo: 24º07'S 45º51'W, 147 m: 70 specimens, coll. 0 9 January 1998; 24º07'S 44º42'W, 101 m: 21 specimens, coll. 11 January 1998; 25º11'S 47º08'W, 157 m: 40 specimens, coll. 16 December 1997; 25º17'S 46º55'W, 60 m: 1 specimen, coll. 16 December 1997; 25°22'S 46°47'W, 70 m: 5 specimens, coll. 16 December 1997. State of Paraná: 27º07'S 47º44'W, 102 m: 1 specimen, coll. 13 March 1998. State of Santa Catarina: 28º41'S 48º18'W, 104 m: 1 specimen, coll. 22.March 1998. Project ‘ BIOTA ’: State of São Paulo: Ubatuba, sublittoral, 23°24'366''S 45°51'431''W, 16.6 m: 1 specimen, coll. 17 November 2001; 23°25'663''S 44°46'570''W, 35 m: 1 specimen, coll. 10 April 2001; 23°25'785''S 44°46'738''W, 35 m: 1 specimen, coll. 17 March 2001; 23°32'765''S 44°44'380''W, 43.8 m: 5 specimens, coll. 10 June 2001. Caraguatatuba, Praia de Martim de Sá (23°37'34''S 45°22'31''W), on rocky shore, intertidal: 1 specimen, coll. 13 March 2001; on Dyctiota sp.: 1 specimen, coll. 16 March 2001. São Sebastião, sublittoral, 23°44'844''S 45°02'451''W, 45 m: 2 specimens, coll. 13 February 2001; 23°56'373''S 45°27'080''W, 44.6 m: 4 specimens, coll. 15 December 2001; 23°56'497''S 45°28'339''W, 45.1 m: 2 specimens, coll. 16 May 2001. Project ‘ Poly-Phytal ’: State of Espírito Santo: Vitória, Praia da Direita, Ilha do Boi (20°18'S 40°17'W), rocky shore, intertidal, on Arthrocardia gardnerii : 2 specimens ( MZUSP 1321), coll. 26 May 2005; 2 specimens ( MZUSP 1322), coll. 0 1 November 2005; on Centroceras clavulatum : 2 specimens ( MZUSP 1320), coll. 0 1 November 2005; on Hypnea musciformis : 1 specimen ( MZUSP 1323), coll. 0 1 November 2005. Project ‘ HABITATS ’: State of Rio de Janeiro (Campos Basin), Van Veen grab; 21°22'58"S 40°19'41"W, 53 m: 2 specimens, coll. 0 5 March 2009, 3 specimens, coll. 0 6 March 2009, 4 specimens, coll. 21 July 2009; 21°23'2"S 40°15'9"W, 145 m: 1 specimen, coll. 0 6 March 2009; 21°59'4"S 40°25'11"W, 52 m: 4 specimens, coll. 25 February 2009, 2 specimens, coll. 0 6 July 2009; 22°1'9"S 40°31'55"W, 49 m: 2 specimens, coll. 24 July 2009; 22°3'41"S 40°24'9"W, 55 m: 27 specimens, coll. 25 February 2009, 1 specimen, coll. 0 6 July 2009; 22°4'14"S 40°6'59"W, 91 m: 1 specimen, coll. 25 February 2009; 22°6'55"S 40°38'59"W, 53 m: 42 specimens, coll. 26 February 2009, 12 specimens, coll. 17 July 2009; 22°7'43"S 40°18'46"W, 73 m: 1 specimen, coll. 24 February 2009; 22°12'17"S 40°14'39"W, 96 m: 1 specimen, coll. 15 March 2009, 2 specimens, coll. 24 July 2009; 22°12'53"S 40°51'13"W, 52 m: 23 specimens, coll. 26 February 2009, 2 specimens, coll. 17 July 2009; 22°17'42"S 40°26'59"W, 104 m: 1 specimen, coll. 23 February 2009; 22°37'35"S 41°21'51"W, 53 m: 4 specimens, coll. 27 February 2009; 22°41'46"S 41°53'45"W, 29 m: 1 specimen, coll. 16 March 2009, 1 specimen, coll. 12 July 2009; 22°45'49"S 41°45'33"W, 53 m: 3 specimens, coll. 16 July 2009; 22°46'54"S 41°3'33"W, 78 m: 8 specimens, coll. 28 February 2009; 22°55'8"S 42°0'49"W, 29 m: 6 specimens, coll. 28 February 2009, 5 specimens, coll. 15 July 2009; 22°59'47"S 41°21'7"W, 77 m: 2 specimens, coll. 21 February 2009; 23°6'51-58"S 41°55-53'W, 111 m: 4 specimens, coll. 0 1 March 2009, 9 specimens, coll. 16 March 2009. Project ‘ BioPol-NE ’: State of Paraíba: Mataraca, Barra de Camaratuba (06º36'S 34º57'W), intertidal: 2 specimens ( MZUSP 2095), coll. 12 August 2010. Baía da Traição, Praia do Farol (06º41'S 34º55'W), intertidal: 6 specimens ( MZUSP 2086), coll. 0 9 August 2010. Rio Tinto, Barra de Mamanguape (06º45'S 34º55'W), intertidal: 2 specimens ( MZUSP 1327), coll. 11 August 2010. Cabedelo, Píer de Cabedelo (06º58'S 34º50'W), intertidal: 2 specimens, coll. 12 February 2009. João Pessoa, Cabo Branco (07o08'S 34o47'W), intertidal: 4 specimens ( MZUSP 1326), coll. 0 9 February 2009, 7 specimens ( MZUSP 1328), coll. 0 2 February 2010; in Tedania sp.: 1 specimen, coll. 0 9 February 2009; Recife do Picãozinho (07°4.243'S 34°49.291'W), intertidal: 1 specimen ( MZUSP 1325), coll. 15 September 2009. Conde, Praia de Carapibus (07º17'S 34º48'W), intertidal, in rhodoliths: 1 specimen ( MZUSP 2092); on algae: 3 specimens coll. 0 9 February 2009; Praia do Coqueirinho (07º18'S 34º47'W), intertidal: 2 specimens ( MZUSP 2087), coll. 28 August 2011; Praia de Jacumã (07º14'S 34º47'W), intertidal: 6 specimens ( MZUSP 2094), coll. 29 January 2010; Praia de Tabatinga (07°19.297'S 34°47.862'W), intertidal: 2 specimens ( MZUSP 2088), coll. 17 September 2012, 2 specimens ( MZUSP 2093), coll. 0 1 September 2011; Praia de Tambaba (07°21'S 34°47'W), 4 specimens ( MZUSP 2091), coll. 30 August 2011. Pitimbu, Farol de Pitimbu (7°28.362'S 34º47'W), 1 m: 2 specimens ( MZUSP 2090), coll. 18 September 2012. State of Pernambuco, Goiana, Pontas de Pedra (07°37'S 34°48'W), 16 specimens ( MZUSP 2085), coll. 13 December 2012. Ilha de Itamaracá, Recifes de Itamaracá, (07°43.944'S 34°49.200'W), 1 m: 2 specimens ( MZUSP 2089), coll. 15 December 2012.

Description. Body thin, elongated, longest specimens ca. 5.6 mm long and 0.2 mm wide, with up to 45 chaetigers. Palps triangular, distally rounded ( Figs 9 A, 10A–C), almost totally fused, with conspicuous line of fusion and distal notch ( Fig. 9 A). Prostomium pentagonal to ovate, slightly shorter than palps, with two pairs of eyes in trapezoidal arrangement ( Fig. 9 A); anterior eyespots absent; antennae inserted close to each other in nearly transverse row, median antenna inserted anteriorly to anterior pair of eyes, elongated, shorter than palps, subdistally inflated with tapered tip ( Figs 9 A, 10A, G); lateral antennae inserted slightly anterior to median antenna, ovate to papilliform, ca. ¼–½ length of median antenna ( Figs 9 A, 10A, G). Ciliated nuchal organs located dorsolaterally between prostomium and peristomium ( Fig. 10 A, G–H). Peristomium similar in length to following chaetigers, sometimes covering posterior part of prostomium, including posterior pair of eyes; peristomial cirri similar to lateral antennae but smaller ( Figs 9 A, 10A, B). Dorsal cirri ovate, slightly larger than peristomial cirri, progressively longer posteriorwards, present on all chaetigers ( Figs 9 A, 10A). Ventral cirri similar to dorsal cirri but shorter, ca. 2/3 length of parapodial lobes ( Fig. 10 B). Parapodial lobes blunt ( Fig. 10 D); anterior parapodia with 1–3 spiniger-like chaetae and 6–8 falcigers each, midbody parapodia with single spiniger-like chaeta and 3–4 falcigers each ( Fig. 11 D), posterior parapodia with single spiniger-like chaeta and 2–3 falcigers each ( Fig. 11 F). Shafts of anterior spiniger-like chaetae with conspicuous spines, posterior spines shorter ( Figs 9 B, 11C); shafts of spiniger-like chaetae on midbody with distal longitudinal lines forming grooves ( Figs 9 C–D, 11D); all blades with short spines ( Figs 9 B, 11C), blades 45–22 µm long on anterior body, 50–25 µm on midbody and 32–15 µm on posterior. Shafts of anterior falcigers subdistally enlarged and spinulated ( Figs 9 B, 11A–B), shafts of posterior falcigers also subdistally enlarged, but with fewer spines, shafts of falcigers on mid- and posterior body with distal longitudinal lines forming grooves ( Figs 9 C–D, 11D–E). Blades of falcigers spinulated and bidentate, subdistal tooth larger ( Figs 9 B–D, 11A–F); blades with dorsoventral gradation in length, 10–3 µm long on anterior, 8–3 µm long midbody, and 5–2 µm long on posterior body. Dorsal simple chaetae present on all chaetigers, sigmoid, subdistally spinulated, with acute tip, stouter posteriorwards ( Figs 9 E–F, 11D, F, H); ventral simple chaetae present only on posterior chaetigers, sigmoid, bidentate, subdistal tooth larger ( Figs 9 G, 11G). Anterior parapodia with up to two aciculae each, one straight, with acute tip, other slightly bent subdistally, with inflated, rounded tip ( Fig. 9 H); midbody and posterior parapodia with single acicula each, of the second type, stouter posteriorwards ( Fig. 9 I). Ciliated pygidium with a pair of thin, elongate anal cirri ( Fig. 10 E–F). Pharynx through 4–5 segments, tooth at anterior border ( Figs 9 A, 10B–C); anterior margin of pharynx surrounded by papillae and fringe of cilia ( Fig. 10 B–C); proventricle extending for 2–5 chaetigers ( Fig. 9 A), with ca. 22 rows of muscle cells ( Fig. 9 A).

Remarks. Exogone dispar is similar to the sympatric E. breviantennata and E. africana but differs from both in having an elongated median antenna. Exogone rolani also share some characters with E. dispar (see 'Remarks' of the former species). Exogone arenosa , E. gigas sp. n. and E. lourei , which also occur along the Brazillian coast, all have a triangular process on the shafts of the spiniger-like chaetae of chaetiger 2, which is absent in E. dispar . More detailed comparisons between E. dispar and other species in this genus are provided by Perkins (1981) and San Martín (1991, 2003, 2005), among several others.

Brazilian specimens of E. dispar differ from Australian ones by having longer blades of the spiniger-like chaetae, 50–22 µm vs. 29–28 µm, as in Australian material ( San Martín 2005).

Type locality. Northampton, Virginia ( USA, Atlantic Ocean).

Distribution. Atlantic Ocean: USA, Mexico, Panamá, Brazil (Paraíba, Pernambuco, Bahia, Espírito Santo, São Paulo), South Africa; North Sea: Skagerrak; Mediterranean Sea: Iberian Peninsula, Italy; Caribbean Sea: Cuba, Trinidad and Tobago. Pacific Ocean: Mexico (Baja California), Galápagos Islands, China, Japan. Indian Ocean: Australia (Western Australia). From the intertidal zone to ca. 157 m deep.

Figures

FIGURE 9. Exogone dispar. (A) Anterior body, dorsal view; (B) compound chaetae, anterior body; (C) compound chaetae, midbody; (D) compound chaetae, posterior body; (E) dorsal simple chaeta, anterior body; (F) dorsal simple chaeta, posterior body; (G) ventral simple chaeta, posterior body; (H) aciculae, anterior body; (I) acicula, posterior body. Scale bars: A, 200 Μm; B – I, 10 Μm.

FIGURE 10. Exogone dispar, SEM. (A) (B) anterior body, dorsal and ventral views, respectively; (C) detail of pharynx, frontal view; (D) midbody, dorsal view; (E) posterior body, dorsal view; (F) posterior end, frontal view; (G) anterior end, lateral view; (H) nuchal organ, lateral view. Scale bars: A – B, D, G, 50 Μm; C, F, 20 Μm; E, H, 100 Μm.

FIGURE 11. Exogone dispar, SEM. (A) (B) falcigers, anterior body; (C) compound chaetae, chaetiger 3; (D) chaetae, midbody parapodium (E) falcigers, midbody parapodium; (F) chaetae, posterior body parapodium; (G) ventral simple chaeta, posterior body; (H) dorsal simple chaeta, posterior body. Scale bars: A, H, 2 Μm; B, E, G, 5 Μm; C, 10 Μm; D, F, 20 Μm.