Sphaerosyllis monicae, Barroso, Rômulo, Paiva, Paulo Cesar De, Nogueira, João Miguel De Matos & Fukuda, Marcelo Veronesi, 2017

Barroso, Rômulo, Paiva, Paulo Cesar De, Nogueira, João Miguel De Matos & Fukuda, Marcelo Veronesi, 2017, Deep sea Syllidae (Annelida, Phyllodocida) from Southwestern Atlantic, Zootaxa 4221 (4), pp. 401-430 : 417-419

Sphaerosyllis monicae sp. nov.

Figure 10

Material examined. Project ' Oceanprof '. 22°04’32.8”S, 39°54’11.4”W, 722 m deep: 1 spec. (ZUEC POL 19882, Holotype), 30 Jun 2003.

Description. Body filiform, holotype 3 mm long, 0.2 mm wide, complete, with 47 chaetigers. Dorsum scattered with few short, digitiform papillae, more evident dorso-laterally. Palps completely fused, distally rounded. Prostomium shorter than palps, rectangular, with two pairs of eyes in trapezoidal arrangement, anterior eyespots absent. Antennae all about same size, median antenna inserted slightly posteriorly to lateral ones ( Fig. 10 A). Peristomium covering the posterior part of prostomium, including part of posterior eyes. Antennae, peristomial and dorsal cirri throughout with similar morphology, basally bulbous, with elongate, thin tip. Dorsal cirri absent on chaetiger 2; thin, digitiform ventral cirri, shorter than dorsal cirri, of uniform length throughout. Parapodial lobes rectangular to distally rounded; parapodial glands absent. Anterior parapodia with 5–6 falcigers each, midbody with 4–5, posterior parapodia with 3–4 falcigers each; anterior body falcigers with subdistally spinulated shafts, especially dorsalmost ones; from midbody parapodia onwards, falcigers with smooth shafts; blades of dorsalmost and intermediate falcigers poorly spinulated, ventralmost falcigers with smooth blades; blades unidentate, except for some sub-bidentate dorsalmost falcigers on posterior body chaetigers, with prominent subdistal spine; blades 30–10 µm long on anterior body, 25–15 µm on midbody, and 15–10 µm long on posterior body ( Fig. 10 B–C). Dorsal simple chaetae on all chaetigers, subdistally spinulated ( Fig. 10 D); ventral simple chaetae present from midbody chaetigers, sigmoid, smooth ( Fig. 10 E). Parapodia all with single acicula each, distally bent at 90°, aciculae progressively stouter towards posterior body ( Fig. 10 F). Pygidium with 1 pair of anal cirri slightly larger than posterior body dorsal cirri ( Fig. 10 G). Pharynx through 2 chaetigers, with conical tooth near anterior border; proventricle extending for 3 chaetigers, with ca. 17 rows of muscle cells ( Fig. 10 A).

Remarks. Sphaerosyllis monicae sp. nov. differs from all known species of Sphaerosyllis by the complete absence of both parapodial glands and papillae over the body and parapodia, as well as by the morphology of falcigers and aciculae.

Sphaerosyllis austriaca Banse, 1959 , S. pirifera Claparède, 1868 and S. piriferopsis Perkins, 1981 are the most similar species to S. monicae sp. nov. due to the absence of parapodial glands. However, all these species have the body dorsally covered by papillae ( San Martín 1984a, 2003), while in S. monicae sp. nov. the dorsal surface of the body is completely smooth.

Sphaerosyllis bulbosa Southern, 1914 , is also similar to Sphaerosyllis monicae sp. nov. regarding the absence of dorsal papillae. However, S. bulbosa presents much shorter falciger blades (up to 10 µm long), secondarily simple chaetae on midbody, apparently by the loss of blades and enlargement of shafts, and aciculae straight, subdistally enlarged ( San Martín 2003).

Although we only have one specimen, we prefer to describe it as a new species, given the unusual and unique set of characters it presents, and the difficulties in collecting more material from the locality where the specimen was found.

Geographic distribution and bathymetric range. Sphaerosyllis monicae sp. nov. is only known from the Campos Basin, at 722 m deep.

Etymology. This species is dedicated to Mônica Petti, a great Brazilian polychaetologist, for her relevant contribution to the knowledge of polychaetes.

Figures

FIGURE 10. Sphaerosyllis monicae sp. nov. (A) anterior end and midbody, dorsal view; (B – C) falcigers, anterior and posterior body chaetigers, respectively; (D) dorsal simple chaeta; (E) ventral simple chaeta; (F) acicula; (G) posterior end, dorsal view.