Exogone simplex Hartmann-Schröder, 1960

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 : 508-510

Exogone simplex Hartmann-Schröder, 1960

( Figure 5 )

Exogone simplex Hartmann-Schröder, 1960: 107 –108, pl. 15, figs 134–136.

Exogone (Sylline) simplex . San Martín 2005: 146, fig. 92; Fukuda 2010: 152 –153, fig. 45.

Material examined. Project ‘BioPol-SP ’: Guarujá, Praia de Pernambuco (23°58'S 46°11'W), intertidal: 2 specimens, coll. 0 4 October 2005. Project ‘BioPol-NE ’: State of Paraíba, Baía da Traição, Praia do Farol (06º41'S 34º55'W), intertidal: 1 specimen ( MZUSP 1337), coll. 0 9 August 2010. João Pessoa, Cabo Branco (07o08'S 34o47'W), on rocky shore, intertidal: 1 specimen ( MZUSP 1338), coll. 0 2 February 2010.

Additional material examined. Exogone simplex . Egypt, Ghardaqa – holotype (ZHM P- 14704), coll. Remane & Schulz, 29 March 1956.

Description. Small species, longest specimens ca. 1.6 mm long and 0.1 mm wide, with up to 18 chaetigers. Palps narrower than anterior chaetigers, distally rounded, totally fused with conspicuous line of fusion ( Fig. 5 A). Prostomium ovate, slightly shorter than palps, with two pairs of eyes in trapezoidal arrangement; anterior eyespots absent; antennae inserted in nearly transverse row, close to each other, anterior to anterior pair of eyes; median antenna digitiform, slightly longer; lateral antennae papilliform, inserted slightly anterior ( Fig. 5 A). Peristomium shorter than following chaetigers, sometimes covering posterior part of prostomium, including posterior eyes; peristomial cirri short, papilliform ( Fig. 5 A). Dorsal cirri ovate, slightly larger than peristomial cirri, absent on chaetiger 2 ( Fig. 5 A). Ventral cirri similar to dorsal cirri but shorter. Parapodial lobes conical, short; anterior parapodia with 3–5 chaetae each, midbody parapodia with 3 chaetae each, posterior parapodia with 2–3 chaetae each; chaetae lacking blades, distally spinose, one spine larger than remaining, chaetae distally inflated and bent ventralwards ( Fig. 5 D). Dorsal simple chaetae present on all segments, subdistally inflated, with acute tip, stouter posteriorwards ( Fig. 5 C). Ventral simple chaetae present on all chaetigers, thinner than other chaetae of the same parapodium, sigmoid, bidentate, subdistal tooth larger than distal tooth ( Fig. 5 G). Single acicula per parapodium throughout, subdistally inflated, with acute tip, thicker in posterior chaetigers ( Fig. 5 F). Pygidium with thin, elongate pair of anal cirri ( Fig. 5 B). Pharynx through two segments; tooth at anterior border; proventricle extending for one chaetiger, with ca.14 rows of muscle cells ( Fig. 5 A).

Remarks. Exogone simplex is similar to E. aquadulcensis in the length of the palps, antennae, peristomial and dorsal cirri throughout, pharynx and proventricle, including the number of muscle-cells and number of aciculae per parapodium, as well as in the absence of dorsal cirri on chaetiger 2. However, E. simplex has chaetae lacking blades throughout, subdistally inflated aciculae with acute tip, and bidentate ventral simple chaetae, while E. aquadulcensis has bayonet chaetae on chaetigers 1–3 and dorsalmost chaetae of the remaining parapodia with slender blades, distally thickened and asymmetrical aciculae with short tip, and unidentate and slightly serrated ventral simple chaetae ( Pascual et al. 1996).

Specimens from Paraíba differ from the Australian ones described by San Martín (2005), in that the latter have only three chaetae per parapodium and the proventricle extending for two chaetigers, whereas those from Paraíba have up to five chaetae per parapodium and a shorter proventricle that extends only through one chaetiger.

Type locality. Egypt, Ghardaka (Red Sea).

Distribution. Atlantic Ocean: Angola, Brazil (Paraíba and São Paulo). Pacific Ocean: Australia (New South Wales). Indian Ocean: Australia (Western Australia); Red Sea: Egypt. Found in the intertidal zone.

Figures

FIGURE 5. Exogone simplex. (A) Anterior end, dorsal view; (B) posterior end, dorsal view; (C) dorsal simple chaeta, anterior body; (D) chaetae throughout; (E) dorsal simple chaeta, mid- and posterior body; (F) acicula; (G) ventral simple chaeta, posterior body. Scale bars: A – B, 50 Μm; C – G: 10 Μm.