Exogone africana Hartmann-Schröder, 1974

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 : 512-514

Exogone africana Hartmann-Schröder, 1974

( Figure 6 )

Exogone verugera africana Hartmann-Schröder, 1974: 137 , figs 164–168.

Exogone (Exogone) a fricana. San Martín 2005: 143–145, figs 90–91; Fukuda 2010: 112–115, fig. 30. Exogone africana . Abd Elnaby & San Martín 2010: 135–136, fig. a–i.

Material examined. Project ‘ BioPol-SP ’: State of São Paulo: Guarujá, Praia de Pernambuco (23°58'20''S 46°11'02''W): 28 specimens, coll. 0 4 October 2005. Santos, Ilha das Palmas (24°00'34''S 46°19'25''W): 11 specimens, 0 5 October 2005. Project ‘ BIOTA’: State of São Paulo: Ubatuba, Praia de Picinguaba (23°22'31''S 44°50'21''W), on rocky shore, intertidal: 2 specimens, coll. 10 May 2001; 5 specimens, coll. 17 October 2001; on Sargassum sp.: 12 specimens, coll. 18 October 2001; on assemblage of algae: 7 specimens, coll. 0 8 June 2001; 3 specimens, coll. 0 8 October 2001; 2 specimens, coll. 18 October 2001. Caraguatatuba, Praia Martim de Sá (23°37'34''S 45°22'31''W), on rocky shore, intertidal: 128 specimens, coll. 19 September 2001; 27 specimens, coll. 21 September 2001; on Sargassum sp.: 1 specimen, coll. 16 March 2001; 3 specimens, coll. 27 September 2001; Ponta do Cambiri (23°37’S 45°24’31”W), on rocky shore, intertidal: 13 specimens, coll. 15 March 2001; 8 specimens, coll. 20 September 2001. São Sebastião, Praia da Baleia (23°46'48''S 45°39'51''W), on rocky shore, intertidal: 152 specimens, coll. 0 8 April 2001; 4 specimens, coll. 0 9 April 2001; 2 specimens, coll. 10 April 2001; 3 specimens, coll. 12 December 2001; 2 specimens, coll. 13 December 2001; on Sargassum sp.: 91 specimens, coll. 10 April 2001; 28 specimens, coll. 14 November 2001. Praia de Toque-Toque Grande (23°50'12''S 45°30'40''W), on rocky shore, intertidal: 26 specimens, coll. 10 April 2001. Project ‘ Poly-Phytal ’: State of Espírito Santo, Vitória, Ilha do Boi, Praia da Direita (20°18'S 40°17'W), rocky shore, intertidal: on Arthrocardia gardnerii : 1 specimen ( MZUSP 1331), coll. 26 May 2005; 6 specimens ( MZUSP 1333), coll. 0 1 March 2006; on Colpomenia sinuosa : 1 specimen ( MZUSP 1332), coll. 21 July 2005; on Sargassum sp.: 1 specimen ( MZUSP 1334), coll. 0 1 March 2006. Project ‘ BioPol-NE ’: State of Paraíba, Rio Tinto, Barra de Mamanguape (06º45'S 34º55'W), intertidal: 1 specimen ( MZUSP 1329), coll. 11 August 2010; Baía da Traição, Praia do Farol (06°41.331'S 34°55.803'W), intertidal: 1 specimen ( MZUSP 1330), coll. 0 9 August 2010. State of Pernambuco, Ilha de Itamaracá, Recifes de Itamaracá, (07°43.944'S 34°49.200'W), 1 m: 25 specimens ( MZUSP 2060), coll. 15 December 2012.

Description. Body thin, elongated, longest specimens ca. 3 mm long and 0.3 mm wide, with up to 40 chaetigers. Palps triangular, distally rounded, totally fused, with a line of fusion ( Fig. 6 A). Prostomium pentagonal to ovate, shorter than palps, with two pairs of eyes in trapezoidal arrangement, anterior eyespots absent; antennae inserted close to each other, in transverse row between anterior pair of eyes, antennae papilliform, median antenna slightly longer ( Fig. 6 A). Peristomium shorter than following chaetigers, usually covering posterior part of prostomium; peristomial cirri similar to lateral antennae but smaller ( Fig. 6 A). Dorsal cirri ovate, similar in length to median antenna, present on all chaetigers ( Fig. 6 A). Ventral cirri similar to dorsal cirri but smaller, shorter than parapodial lobes. Parapodial lobes conical; anterior parapodia with 1–2 spiniger-like chaetae and 3–5 falcigers each, midbody and posterior parapodia with single spiniger-like chaeta and 2–3 falcigers each; shafts of spinigerlike chaetae subdistally inflated and spinulated; blades of spiniger-like chaetae distally bifid, with minute teeth, spinulated, blades ca. 28 µm long on anterior body, 45–50 µm long on midbody, and 20–24 mm long on posterior body ( Fig. 6 B–D); shafts of falcigers subdistally inflated, spinulated; blades of falcigers spinulated, bidentate; blades with slight antero-posterior gradation in length, 7–10 mm long on anterior body, ca. 8 mm on midbody, and ca. 7 mm long on posterior body ( Fig. 6 B–D). Dorsal simple chaetae present on all chaetigers, sigmoid, subdistally spinulated, with acute tip, stouter posteriorwards ( Fig. 6 E–F); ventral simple chaetae present only in posterior parapodia, sigmoid, bidentate, subdistal tooth larger ( Fig. 6 G). Anterior parapodia with up to two aciculae each, both slightly curved subdistally, with inflated, rounded tip ( Fig. 6 H); midbody and posterior parapodia with single acicula each, of same shape ( Fig. 6 I), stouter posteriorwards. Pygidium with thin, elongate pair of anal cirri ( Fig. 6 J). Pharynx through three segments; tooth at anterior border; anterior margin of pharynx surrounded by papillae; proventricle extending for four chaetigers, with ca. 22 rows of muscle cells ( Fig. 6 A).

Remarks. Exogone africana is very similar to E. breviantennata , E. dispar , and E. verugera . Exogone breviantennata is the most similar species, as both taxa share papilliform antennae, peristomial, dorsal and ventral cirri throughout; the same number of aciculae, spiniger-like and falciger chaetae per parapodium; similar morphology of aciculae, dorsal and ventral simple chaetae; pharynx of similar length; and proventricle with approximate number of muscle-cell rows. However, E. breviantennata is proportionally more slender, also differing from E. africana by having blades on anterior falcigers with fewer, but somewhat stouter spines, and shorter proventricle. Studying the fauna of Australia, San Martín (2005) pointed out that young specimens of these species can be easily mixed up, noticing that E. breviantennata was found only in tropical areas, where E. africana was less abundant. In the present study, E. breviantennata was more abundant than E. africana , thus supporting the pattern noticed by San Martín (2005).

Exogone dispar also has papilliform lateral antennae, peristomial, dorsal and ventral cirri throughout; a similar number of aciculae, spiniger-like and falciger chaetae per parapodium; aciculae, dorsal and ventral simple chaetae with similar morphology; pharynx of similar length; and proventricle with approximately the same number of muscle-cell rows as in E. africana . The differences between E. africana and E. dispar include the shorter proventricle of the latter species, as well as E. dispar having falciger blades that are more spinulated, and a median antenna distinctly longer than the lateral antennae.

The Brazilian specimens agree with the original description and that provided for an Australian specimen by San Martín (2005).

Type locality. Republic of Namibia, Luderitz (Atlantic Ocean).

Distribution. Atlantic Ocean: Namibia, Angola, Brazil (Paraíba, Pernambuco, Espírito Santo, São Paulo); Mediterranean Sea: Egypt and Turkey. Pacific Ocean: USA (Hawaii); Japan; Australia (Queensland, New South Wales). Indian Ocean: Australia (Western Australia). From the intertidal zone to ca. 81 m deep.

Figures

FIGURE 6. Exogone africana. (A) Anterior end, 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; (J) posterior end, dorsal view. Scale bars: A, 200 Μm; B – I, 10 Μm, J = 25 Μm.