Odontosyllis guarauensis, Fukuda, Marcelo Veronesi, Nogueira, João Miguel De Matos, Paresque, Karla & Martín, Guillermo San, 2013

Fukuda, Marcelo Veronesi, Nogueira, João Miguel De Matos, Paresque, Karla & Martín, Guillermo San, 2013, Species of Odontosyllis Claparède, 1863 (Annelida: Polychaeta: Syllidae) occurring along the Brazilian coast, Zootaxa 3609 (2), pp. 142-162 : 154-160

Odontosyllis guarauensis sp. nov.

Figures 1 C; 4–7; Table 3

Material examined. Project ‘BIOTA’. Ubatuba—Praia de Picinguaba (23°22’31”S 44°50’21”W), on rocky shore: 1 spec. (MZUSP 1239), 10 May 2001; 4 specs (MZUSP 1025), 17 Oct 2001; 1 spec. (MZUSP 1240), 18 Oct 2001. São Sebastião—Praia da Baleia (23°48’54”S 45°39’51”W), on Sargassum : 4 specs (MZUSP 1222), 14 Nov 2001. Project ‘BioPol-SP’. Ubatuba—Praia de Domingas Dias (23°30’00”S 45°08’38”W): 1 spec. (MZUSP 1023), 2 Nov 2002. São Sebastião—Praia da Baleia (23°48’54”S 45°39’51”W): 1 spec. (MZUSP 1241), 23 Jul 2005; Praia de Toque-Toque Grande (23°50’12”S 45°30’40”W): 1 spec., 21 Jul 2005. Guarujá—Praia de Pernambuco (23°58’20”S 46°11’02”W): 2 specs (MZUSP 1024), 22 Jun 2006. Itanhaém—Praia do Sonho (24°11’44”S 46°48’05”W): 3 specs, 26 Aug 2003. Peruíbe—Praia do Guaraú (24°22'02"S 47°00'35"W), intertidal, in Bostrychia sp.: 97 specs (MZUSP 1020, holotype; MZUSP 1021, paratype 1; ZUEC-POL 11893, paratype 2; MNCN 16.01/14459, paratype 3; ZUEC-POL 11894, paratype 4; MNCN 16.01/14460, paratype 5; MZUSP 1022, thirty paratypes; ZUEC-POL 11895–11897, thirty paratypes; MNCN 16.01/14461, twenty paratypes), 19 May 2008.

Type series. Data of selected specimens of the type series are provided in Table 3.

Additional material examined. Odontosyllis polycera (Schmarda, 1861) . Indian Ocean, Australia: Western Australia, Albany, Frenchman Bay, Goode Beach: 1 spec. (ZMH P-18131), coll. & det. G. Hartmann-Schröder, 21 Nov 1975; South Australia, Port Lincoln: 2 specs (ZMH P-18550), coll. & det. G. Hartmann-Schröder, 3 Dec 1975; South Australia, Port MacDonnel, Cape Northumberland: 1 spec. (ZMH P-18772), coll. & det. G. Hartmann- Schröder, 18 Dec 1975.

Description. Medium-sized body, holotype largest specimen collected, 9 mm long, 0.70 mm wide, with 81 segments (Table 3). Conspicuous pigmentation on living animals, as nearly triangular patch on prostomium, below occipital flap, and large dark spots scattered across dorsum, roughly arranged in one broad transverse stripe mostly on anterior half of each chaetiger ( Fig. 5 A); pigmentation slightly fading after preservation ( Fig. 4 A). Palps rounded to kidney-shaped, basally fused, each with two rows of cilia, one close to posterior border, another at midlength, present dorsally and ventrally, additional tufts of cilia on internal side of each palp dorsally, from midlength to tip ( Figs 5 C–F; 6A–C). Prostomium ovate with two pairs of eyes in rectangular to trapezoidal arrangement and one pair of small anterior eyespots; lateral antennae inserted on anterior margin of prostomium, as long as palps or slightly longer; median antenna inserted slightly anteriorly to middle of prostomium, ~1.5 times as long as lateral antennae ( Figs 4 A; 5A–F; 6A–C); nuchal organs as one pair of broad semi-circular rows of cilia posterior to eyes of posterior pair, extending dorsally below occipital flap and laterally around prostomium, until close to base of palps ( Figs 5 D–F; 6B); prostomium with additional pair of rows of cilia between anterior and posterior pairs of eyes ( Figs 5 D; 6B–C). Peristomium dorsally short, with large, roughly rectangular occipital flap almost as wide as prostomium, covering posterior and, sometimes, anterior pairs of eyes ( Figs 4 A; 5A–B, D–F; 6B–C); dorsal peristomial cirri slightly longer than median antenna, ventral peristomial cirri about as long as median antenna, in ventro-lateral position, laterally to mouth ( Figs 4 A; 5C–F; 6A–C). Dorsal cirri of chaetiger 1 inserted dorsally to following cirri, 1.5–2 times as long as median antenna, dorsal cirri throughout about as long as median antenna, alternating longer and shorter cirri, longer cirri directed upwards and inserted dorsally to shorter cirri ( Fig. 5 F). Antennae, peristomial and anterior dorsal cirri with minute tufts of cilia ( Figs 5 D–F; 6A–E); peristomial and dorsal cirri with short cirrophores ( Figs 5 D–F; 6A–E). Ventral cirri short, ovate, not extending beyond parapodial lobes ( Figs 5 C; 6A–B, D). Parapodia distally bilobed ( Figs 5 C, F; 6A–B, D), lobes about same size or posterior lobe slightly larger. Anterior parapodia with 12–18 falcigers each, midbody with 9–15, posterior parapodia with 4–9 falcigers each (Table 3); falcigers with subdistally spinulated shafts; from midbody, shafts of dorsalmost falcigers with subdistal, nearly triangular enlargement and thin, straight tip ( Figs 1 C; 4C–D; 7E, G); connective between shafts and blades wrinkled to slightly spinulated; falcigers with blades slightly spinulated and bidentate, distal tooth larger than subdistal one ( Figs 4 B–D; 7A–H); blades with inverted dorso-ventral gradation in length, 12–22 μm long on anterior chaetigers, 12–21 μm long on midbody, 10–17 μm long on posterior chaetigers (Table 3). Dorsal simple chaetae only present on posterior chaetigers (Table 3), thin, ~1/5 as thick as shafts of falcigers, poorly spinulated subdistally, distally rounded ( Fig. 7 G); ventral simple chaetae, if present, only on last chaetigers (Table 3), sigmoid, bidentate, tips resembling those of blades of falcigers, about half as thick as shafts of falcigers ( Fig. 7 H). Anterior parapodia with up to three aciculae each, midbody with two, posterior parapodia with one acicula each; aciculae irregularly enlarged distally, with slight progressively increasing thickness towards posterior parapodia ( Fig. 4 E–G). Pharynx through ~4–4.5 segments (Table 3), trepan with 9 teeth and two lateral plates ( Fig. 4 H); proventricle through 5–7.5 segments (Table 3), with numerous packed transverse and oblique muscle cell rows ( Fig. 4 A).

Remarks. Odontosyllis guarauensis sp. nov., belongs to the same group of species as O. aracaensis sp. nov., with short, bidentate falciger blades. However, Odontosyllis guarauensis sp. nov., can be distinguished from most of those species by the morphology of chaetae and trepan, besides the pigmentation pattern (Table 2).

The nearly triangular subdistal enlargement of the shafts of posterior body dorsalmost falcigers of O. guarauensis sp. nov., has never been referred to in other descriptions of species of Odontosyllis , but a similar configuration is present in O. polycera (MVF, pers. obs.). In addition, O. polycera resembles O. guarauensis sp. nov., in the overall body shape, size of the occipital flap, and in the occurrence of falcigers with inverted dorsoventral gradation in lengths of the blades. However, O. polycera differs from O. guarauensis sp. nov., in having falciger blades with a much smaller subdistal tooth, sometimes reduced to an enlarged spine or even absent, while in O. guarauensis sp. nov., the subdistal tooth is always conspicuous, though smaller than the distal one. These differences also apply to the ventral simple chaetae, which have tips similar to those of falcigers. Furthermore, O. polycera has two types of aciculae, one subdistally enlarged, with crown of subdistal spines and short acuminate tip, and another thicker, subdistally oblique and distally rounded, slightly protrudring from parapodial lobes sometimes, while the aciculae of O. guarauensis sp. nov., are all irregularly enlarged distally ( Fig. 4 E–G). Finally, the trepan of O. polycera has 5–8 teeth and 2 lateral plates, while in O. guarauensis sp. nov., it has 9 teeth and 2 lateral plates ( Fig. 4 H).

Etymology. The species is named after the Praia do Guaraú (Guaraú beach, in Peruíbe, State of São Paulo) where it was found in the greatest abundance, frequently crawling over the algae Bostrychia sp.

Conclusions

We herein describe two new species of Odontosyllis , a widespread genus of Syllidae , which is recognized by the usual presence of a peristomial occipital flap covering the posterior part of the prostomium, and by the characteristic trepan with teeth pointing backwards. Identification to species level, however, is considerably more difficult, since many species are defined by different combination of characters, some of them with tenuous morphological variations. Many of the ~49 described species (Verdes et al. 2011) correspond to single reports and some lack informative taxonomic characters (especially the older descriptions). We provide here a list of characters (Table 2) as a first step to encourage a much needed revision of this group.

In our paper we also pay special attention to the morphology of the falciger shafts, which is usually disregarded. In the species of Odontosyllis so far investigated, we noticed three different morphologies for the shafts of posterior body dorsalmost falcigers, which are more evident when comparing the dorsalmost and ventralmost chaetae ( Fig. 1 A–D):

1) subdistally inflated shafts with thin, straight tip ('regular' syllid type) ( Fig. 1 A–B);

2) shafts of dorsalmost chaetae with nearly triangular subdistal enlargement, with thin, straight tip ( Fig. 1 C); 3) shafts of dorsalmost chaetae subdistally inflated with thin, sigmoid tip ( Fig. 1 D).

We suggest that this character should be investigated in other species of Odontosyllis , to check if it could provide useful information to resolve relationships within the genus.

Figures

FIGURE 1. Dorsalmost (left hand) and ventralmost (right hand) falcigers of posterior chaetigers of the species of Odontosyllis treated in the present paper. (A) O. aracaensis sp. nov.; (B) O. cf. fulgurans; (C) O. guarauensis sp. nov.; (D) O. guillermoi. Scale bar = 10 µm.

FIGURE 4. Odontosyllis guarauensis sp. nov. (A) anterior end, dorsal view; (B) falcigers, anterior chaetiger; (C) falcigers, midbody chaetiger; (D) falcigers, posterior chaetiger; (E) aciculae, anterior chaetiger; (F) aciculae, midbody chaetiger; (G) acicula, posterior chaetiger; (H) detail of the pharynx, showing trepan. Scale bars: A = 150 µm; B – G = 10 µm; H = 50 µm.

FIGURE 5. Odontosyllis guarauensis sp. nov. (A) holotype (MZUSP 1020) alive, dorsal view; (B) entire worm, dorsal view; (C) anterior end, ventral view; (D) anterior end, dorsal view; (E) detail of prostomium, peristomium and first chaetigers, right lateral view; (F) anterior end, right lateral view. Scale bars: A = 500 µm; B = 400 µm; C, F = 100 µm; D = 90 µm; E = 60 µm.

FIGURE 7. Odontosyllis guarauensis sp. nov. (A) falcigers, anterior chaetiger; (B) falcigers, midbody chaetiger; (C) dorsalmost falciger, midbody chaetiger; (D) ventralmost falcigers, midbody chaetiger; (E) dorsalmost falciger, posterior chaetiger; (F) ventralmost falcigers, posterior chaetiger; (G) dorsalmost falciger and dorsal simple chaeta, posterior chaetiger (arrow pointing to dorsal simple chaeta); (H) ventralmost falcigers and ventral simple chaeta, posterior chaetiger (arrow pointing to ventral simple chaeta). Scale bars: A – B = 20 µm; C = 5 µm; D – E = 4 µm; F = 9 µm; G – H = 6 µm.