Paranaitis chitinosa Oliveira & Jacobsen & Lana 2018, sp. nov.

Paranaitis chitinosa sp. nov.

Figs 5–7

Holotype. Paranaguá Bay, Paraná, Brazil, 25°30'41.6”S, 48°29’50.3”W, intertidal, Jan. 2010 (ZUEC-POL-16567).

Paratypes. A total of 17 paratypes, ranging from 1–43 mm for 26–97 segments. Paranaguá Bay shoals, Paraná, Brazil: Guaraguaçu River, 15 Jan. 2009 (1 paratype, NHMD-207786); 25°33’031"S, 48°25’074"W, 26 Jan. 2009 (1 paratype, NHMD-207807); same locality, 27 Jan. 2009 (1 paratype, NHMD-207816); Caraguaçu River, Paranaguá Bay, 16 Nov. 2009 (1 paratype, NHMD-207825); 25°33’031"S, 48°25’074"W, Guaraguaçu river in the Cotinga Channel, 17 Nov. 2009 (1 paratype, NHMD-207843); 25°30'41.6”S, 48°29’50.3”W, Jan. 2010 (1 paratype, ZUEC-POL-16569). Margin of continental shelf, Campos Basin: Hab 11 C03 R3, 22°46’54.8”S, 41°3’33.6”W, 78 m, 22 Feb. 2009 (1 paratype, ZUEC-POL-16361); Hab 13 H04 R2, 21°42’53.9”S, 40°10’16.2”W, 98 m, 9 Mar. 2009 (1 paratype, ZUEC-POL-16375); Hab 11 E01 R1, 22°1’46.0”S, 40°44’52.5”W, 27 m, 26 Feb. 2009 (2 paratypes, ZUEC-POL-16398); Hab 11 B02 R2, 22°37’35.3”S, 41°21’51.7”W, 53 m, 27 Feb. 2009 (1 paratype, ZUEC-POL-16416); Hab 11 G04 R2, 22°4’14.3”S, 40°6’59.4”W, 91 m, 25 Feb. 2009 (1 paratype, ZUEC-POL- 16443); Hab 11 D01 R2, 22°6’42.1”S, 40°54’44.1”W, 29 m, 26 Feb. 2009 (2 paratypes, ZUEC-POL-16447); Hab 16 G05 R2, 22°6’10.6”S, 40°3’6.3”W, 149 m, 7 Jul. 2009 (1 paratype, ZUEC-POL-16459); Hab 11 B05 R2, 22°11’28.9”S, 41°0’49.6”W, 117 m, 21 Feb. 2009 (1 paratype, ZUEC-POL-16467); Hab 11 A01 R2, 22°55’7.5”S 42°0’49.2”W, 29 m, 28 Feb. 2009 (1 paratype, ZUEC-POL-16588). Collected on sandy and muddy bottoms, and in the intertidal region, Brazil.

Diagnosis. Proximal part of proboscis with rows of conical, chitinous papillae alternating with long, chitinous papillae; distal extremity covered with micropapillae; terminal ring with oval papillae. Dorsal cirri rounded and asymmetrical, longer than wide. Compound spinigers from segment 3.

Description. Holotype complete, 97 segments, 43 mm long, 2.5 mm wide at median part of body including parapodia and excluding chaetae. Body elongate, dorso-ventrally flattened, with uniform width but slightly tapering at posterior end. Prostomium anteriorly rounded, longer than wide (Fig. 5A). Knob-like nuchal papilla inserted into depression on posterior prostomial margin. Prostomial ligula present. Paired antennae and palps conical, of similar size, postero-laterally placed on prostomium. Antennae and palps 1/4 prostomial length. A pair of rounded eyes, with lenses, at posterior margin of prostomium. Proximal part of proboscis with longitudinal rows of conical, chitinous papillae alternating with long, chitinous papillae, and distal part covered with micropapillae (Fig. 5C–D). First and second segments fused, forming a collar behind prostomium (Fig. 5A). Four pairs of cylindrical tentacular cirri on first three segments, biarticulate, with short cirrophores and long cirrostyles. Cirri of first segment reaching segment 3. Dorsal and ventral cirri of segment 2 reaching segments 3 and 4, respectively. Dorsal cirri of segment 3 extend to segment 5. Segment 2 with aciculae but lacking neuropodial lobes and chaetae (Fig. 5B). Neuropodia with chaetae and ventral cirri from segment 3 (Fig. 6A). Dorsal cirri asymmetrical, with developed cirrophores, from segment 4. Dorsal cirri of median segments rounded and longer than those of anterior and posterior segments (Fig. 6B–D). Neuropodial lobes shorter than dorsal and ventral cirri, with medium lightbrown acicula and bundle of chaetae. Prechaetal lobe bilobate, asymmetrical and rounded; supraacicular lobe longer than subacicular; lobe asymmetry stronger in anterior and median parapodia. Ventral cirri rounded and asymmetrical, horizontally oriented in relation to neuropodial lobe, more elongated on median than on anterior segments, and almost as wide as long on posterior segments (Fig. 6C–D). Compound spinigerous chaetae from segment 3. Rostrum of chaetal shaft with a large and robust main tooth surrounded by denticles (Fig. 7A–B). Pygidium with one pair of cylindrical anal cirri with rounded edges (Fig. 7C), and probably a median pygidial papilla as indicated by an insertion scar (Fig. 7D).

Coloration. Preserved specimens with body having opaque pink pigmentation and appendages light-brown (Fig. 5A).

Distribution. Atlantic Ocean, Brazil: Coroa Grande, Rio de Janeiro. Paranaguá Bay, Mel Island, Paraná, in intertidal regions. Also found on the continental shelf off SE Brazil down to ca. 150 m.

Etymology. The species name is derived from the Greek word chitin, refering to the presence of chitinous bars on the proboscis.

Remarks. Eyes are present in the four new species from Brazilian waters, but they are absent in P. abyssalis Hartmann-Schröder, 1975, P. benthicola Knox, 1960, P. bowersi (Benham, 1927), P. caeca (Moore, 1903), and P. uschakovi Eibye-Jacobsen, 1991. The presence of chitinous papillae on the proboscis, and cylindrical pygidial cirri with rounded edges in Paranaitis chitinosa sp. nov. is shared with P. caeca, P. inflata (Hutchings & Murray, 1984), P. misakiensis, P. moritai Kato & Pleijel, 2003, P. pumila Kato & Pleijel, 2003, and P. uschakovi, but the new species differs from them in the morphology of the dorsal, which are reniform in P. caeca and P. moritai, almost circular P. inflata, and oval in P. misakiensis and P. pumila. The new species shares the presence of one neuropodial acicula in the second segment with P. caeca, P. misakiensis, P. polynoides (Moore, 1909), and P. pumila; however, it differs from P. benthicola and P. moritai because they have notopodial aciculae and neuropodial chaetae in the second segment. Noto- and/or neuropodial aciculae in the second segment are not easily observed in fixed specimens because they are embedded in the muscle tissue and only their distal ends appear in the cirrophores.

Aciculae typically retract in fixed animals. Paranaitis chitinosa sp. nov. differs from P. assimetrica sp. nov., P. cordiformata sp. nov., and P. cirriformata sp. nov. in the morphology of dorsal cirri, which are rounded in P. assimetrica sp. nov. and P. cirriformata sp. nov. and cordiform in P. cordiformata sp. nov.. The pair of cylindrical anal cirri with rounded edges in P. chitinosa sp. nov. is not found in the other Brazilian congeners.