Sphaerosyllis ceciliae Barroso, Paiva, Nogueira & Fukuda, 2017, sp. nov

Sphaerosyllis ceciliae sp. nov

Figure 8–9

Type material. Holotype (MNRJP 1178): 22°26’28.8”S, 39°58’53.3”W, 0–2 cm, 1046 m deep, 20 Jun 2003. Paratypes: 19°53’31”S, 39°32’56”W, 1023 m deep: 48 specs (MZUSP 2964), 13 Jan 2012; 21°4’43”S, 40°8’31”W, 1024 m deep: 24 specs (MZUSP 2965), 30 Dec 2011; 22°40’57.84”S, 40°16’30.35”W, 0–2 cm, 1045 m deep: 2 specs (ZUEC POL 19881), 22 Nov 2002; 22°10’54.6”S, 39°48’59.5”W, 0–2 cm, 1336 m deep: 2 specs (MNRJP 1179), 25 Jun 2003; 22°04’33.9”S, 39°52’05.1”W, 0–2 cm, 1030 m deep: 2 specs (MNRJP 1180), 30 Jun 2003; 21°52’51.8”S, 39°48’12.5”W, 2–5 cm, 1372 m deep: 1 spec. (MNRJP 1181), 26 Jun 2003; 22°31’12”S, 40°15’11”W, 0–2 cm, 722 m deep: 1 spec. (MNRJP 1182), 22 Nov 2002; 22°26’28.5”S, 39°54’08.3”W, 0–2 cm, 1354 m deep: 2 specs (MNRJP 1183), 21 Jun 2003; 22°31’37.2”S, 39°55’14.5”W, 0–2 cm, 1630 m deep: 1 spec. (MNRJP 1184), 16 Jun 2003.

Additional material. Project ‘ AMBES ’. 19°3’29”S, 37°48’39”W, 1302 m deep: 3 specs, 30 Jan 2012; 19°40’8”S, 39°7’22”W, 1035 m deep: 15 specs, 13 Dec 2011; 19°47’5”S, 39°3’11”W, 1258 m deep: 1 spec., 28 Jan 2012; 19°49’37”S, 39°35’41”W, 410 m deep: 1 spec., 14 Jan 2012; 19°50’1”S, 39°26’30”W, 1055 m deep: 10 specs, 11 Jan 2012; 19°52’56”S, 38°35’8”W, 1022 m deep: 10 specs, 17 Dec 2011; 19°54’5”S, 39°22’20”W, 1335 m deep: 1 spec., 11 Jan 2012; 19°58’11”S, 39°31’38”W, 1300 m deep: 5 specs, 13 Jan 2012; 20°4’8”S, 38°31’27”W, 1302 m deep: 2 specs, 21 Dec 2011; 20°15’36”S, 39°46’15”W, 1040 m deep: 30 specs, 9 Jan 2012; 20°17’41”S, 39°42’38”W, 1358 m deep: 2 specs, 9 Jan 2012; 20°36’2”S, 39°51’35”W, 1000 m deep: 49 specs, 8 Jan 2012, and 35 specs, 18 Jun 2013; 20°36’42”S, 39°49’25”W, 1333 m deep: 5 specs, 8 Jan 2012; 21°4’43”S, 40°4’12”W, 1295 m deep: 1 spec., 9 Jun 2013; 21°4’51”S, 40°4’14”W, 1300 m deep: 1 spec., 31 Dec 2011.

Description. Holotype with 40 chaetigers, 2.4 mm long and 0.2 mm wide; complete paratypes with 29–33 chaetigers, 1.4–1.9 mm long, 0.2–0.3 mm wide. Dorsum scattered with small papillae, more conspicuously dorsolaterally (Figs 8 I–J, 9A–B), papillae more elongate towards posterior body (Fig. 9 C). Palps slightly longer than prostomium, almost totally fused, with distal notch, median line well marked (Figs 8 A, I; 9A–B), sometimes with tips ventrally bent. Prostomium rectangular, with 2 pairs of eyes in trapezoidal arrangement; lateral antennae inserted close to anterior border of prostomium, almost reaching tip of palps; median antenna inserted posteriorly to middle of prostomium, slightly longer than lateral antennae, reaching around same level as lateral antennae (Figs 8 A, I; 9A–B). Peristomium slightly shorter than anterior body chaetigers, sometimes forming a fold covering posterior part of prostomium, especially middorsally, reaching base of median antenna (Figs 8 I; 9A–B). Antennae, peristomial and dorsal cirri throughout with similar morphology, basally bulbous and with elongate, thin tip. Dorsal cirri of uniform length throughout, shorter than antennae (Figs 8 A, I–J; 9A–C). Thin, digitiform ventral cirri, shorter than dorsal cirri, of uniform length throughout (Fig. 9 I). From chaetiger 4 onwards, each parapodium with one gland containing fibrilar inclusions, 1 pair per chaetiger, located dorsally to bases of dorsal cirri; glands opening dorsally through prominent papilla, larger than other papillae (Fig. 8 A, I–J). Anterior parapodia with 6–7 falcigers each, midbody with 4–5, posterior parapodia with 2–4 falcigers each; falcigers with distally spinulated shafts, with elongate spines; blades spinulated, with straight spines, approximately of uniform length along blade, more evident on dorsalmost and intermediate falcigers in each fascicle; blades bidentate to sub-bidentate, subdistal tooth much smaller, resembling an enlarged spine, more evident on dorsalmost chaetae; subdistal tooth progressively shorter ventralwards within each fascicle, ventralmost chaetae usually unidentate with a developed subdistal spine (Figs 8 F–H, K–L; 9D, F–I); blades 45–20 µm long on anterior body, 50–20 µm on midbody, and 30–20 µm long on posterior body. Dorsal simple chaetae present from first chaetiger onwards, sigmoid, distally spinulate (Figs 8 C, M; 9E); ventral simple chaetae present from midbody, sigmoid, smooth (Fig. 8 D). Anterior body with 2 aciculae per parapodium, one distally bent at 90°, with acute tip, other straight, distally pointed; single acicula per parapodium in mid- and posterior body chaetigers, of first type; aciculae progressively stouter towards posterior body (Fig. 8 B, E). Pygidium with 1 pair of anal cirri longer and thinner than dorsal cirri. Pharynx through 3–4 chaetigers, with conical tooth on anterior border; proventricle through 3 chaetigers, with ca. 15 rows of muscle cells (Fig. 8 A).

Remarks. Sphaerosyllis ceciliae sp. nov. is similar to S. boeroi Musco, Çinar & Giangrande, 2005, S. hystrix Claparède, 1863, S. parabulbosa San Martín & López, 2002, S. taylori Perkins, 1981, and S. thomasi San Martín, 1984b, due to the fibrilar nature of the inclusions within the parapodial glands. However, S. ceciliae sp. nov. differs from S. parabulbosa, S. taylori and S. thomasi on the morphology of the falcigers, remarkably longer bidentate/ sub-bidentate blades in the new species compared to these congegers; furthermore, S. thomasi and S. taylori present blades more conspicuously spinulated than in S. ceciliae sp. nov. Sphaerosyllis hystrix differs from S. ceciliae sp. nov. in having antennae and cirri throughout proportionally larger than S. ceciliae sp. nov., and the subdistal tooth/ spine of the falciger blades of S. ceciliae sp. nov. is more conspicuous and longer than in S. hystrix, although the spinulation of the blades is more prominent in the latter species.

Sphaerosyllis boeroi, described from the Mediterranean Sea, is probably the most similar species to S. ceciliae sp. nov., but can be distinguished by the longer blades of the midbody falcigers (up to 62.5 µm long in S. boeroi, against up to 50 µm long in S. ceciliae sp. nov.), as well as by the more conspicuous spinulation of the falcigers blades. Furthermore, S. boeroi inhabits shallower environments (5–150 m), when compared to those where S. ceciliae sp. nov. was found (749–1903 m).

The large papilla present above each parapodial gland seems to be connected to the gland, serving as a channel through which the inclusions are discharged to the environment. Many specimens were found with fibrilar components partially extruded through the openings on top of these papillae, and those components are similar to the ones observed by transparency inside the glands.

Geographic distribution and bathymetric range. Sphaerosyllis ceciliae sp. nov. is only known from the Campos Basin (749–1903 m deep).

Etymology. This species is dedicated to Cecilia Amaral, a famous Brazilian polychaetologist, for her essential contribution to the knowledge of Brazilian marine invertebrates, especially polychaetes, as well as her for continuous efforts regarding research and education of new polychaetologists.