Branchiosyllis gonzaguinhai sp. nov.

Figures 6–8; Table 3

Type series. Holotype (MNRJP 1912): Atlantic Ocean, Brazil, state of Pernambuco, Fernando de Noronha Island, Buraco da Raquel (3°50’11”S, 32°24’ 34”W), 1 m depth, on Plakortis insularis, coll. R. Nascimento, 21. April. 2016 . Paratypes: Atlantic Ocean, Brazil, state of Rio Grande do Norte, Rocas Atoll, Piscina das Tartarugas (3°52’20.5”S, 33°48’31.4”W), 1 m depth, on sponges: Paratype 1 (MZUSP 3533), coll. 21. Oct. 2000; Canal da Barretinha (3°51’35.3”S, 33°49’04.6”W), 1 m depth, on sponges : Paratype 2 (MZUSP 3534), Paratype 3 (MNRJP 1913), coll. 10. Oct. 2000; state of Pernambuco, Fernando de Noronha Island, Buraco da Raquel (3°50’11”S, 32°24’ 34”W), 1 m depth, on Aiolochroia crassa: Paratype 4 (MNRJP 1914), Paratype 5 mounted for SEM (MNRJP 1983) coll. R. Nascimento, 21. April. 2016. Morphological data from specimens of the type series provided in Table 3 .

Description. Holotype complete, with 4.6 mm long, 0.40 mm wide, with 52 segments (Figs 6A; 7A; Table 3). Longest specimen analyzed paratype 1 (MZUSP 3533), 6.6 mm long, 0.47 mm wide, with 55 segments (Table 3). Subcylindrical to slightly flattened body (Figs 6A; 7A; 8A). Holotype pigmented, dorsally with brownish spots on prostomium and dark spots on each side of the segments, close to bases of cirrophores (Fig. 6A). Distally rounded palps fused only at bases (Figs 6A, D; 7A; 8B). Prostomium subpentagonal to rectangular, with two pairs of eyes in trapezoidal arrangement (Figs 6A; 7A); antennae inserted on anterior margin of prostomium; median antenna with 13–17 articles, lateral antennae with 13–17 articles each (Figs 6A; 7A; 8A; Table 3). Nuchal organs as pair of densely ciliated rows dorso-laterally located on posterior border of prostomium (Fig. 8C). Peristomium dorsally inconspicuous, covered by chaetiger 1 (Figs 7A; 8C); dorsal peristomial cirri longer than median antenna, with 25–31 articles each (Table 3); ventral peristomial cirri shorter than dorsal ones, with 12–15 articles each (Table 3). Chaetiger 1 with dorsal projections as rounded swollen areas at bases of cirrophores, and a mid-dorsal, triangular projection over peristomium and prostomium (Figs 7A; 8C). Dorsal cirri on chaetiger 1 with 18–25 articles each; on chaetiger 2 with 16–26, on chaetiger 3 with 26–36 articles, on chaetiger 4 with 15–20 articles, and on chaetiger 5 with 17–24 articles each; dorsal cirri slightly alternating in length in remaining chaetigers, longer cirri with up to 34 articles, shorter cirri with up to 20 articles (Figs 6A; 7A; 8A). Ventral cirri digitiform, inserted at midlength of parapodial lobes, not reaching tip of parapodial lobes (Figs 6C; 8B). Parapodia distally bilobate, pre-chaetal lobe larger than post-chaetal one, both digitiform (Fig. 8G). A single branchia per parapodium, dorsally inserted, welldeveloped, multilobulated (Fig. 8A, D–F), with up to five lobes (Fig. 8E), and granular appearance internally. Compound chaetae as ungulae only, regular falcigers absent; anterior body with 4–5 ungulae per parapodium; midbody with 4–6, posterior body with 4–6 ungulae per parapodium (Table 3); ungulae with shafts subdistally slightly spinulated, shafts progressively thicker ventralwards throughout body (Figs 7 C–E; 8G, H); blades unidentate with dorsoventral gradation in length, ventralmost ungulae larger and thicker than dorsalmost ones throughout (Figs 7 C–E; 8H). Aciculae straight, with acute tip, progressively slightly thicker towards posterior body; anterior parapodia with two aciculae each (Fig. 7F); midbody and posterior parapodia with only one acicula each (Fig. 7G, H; Table 3), sometimes slightly protruding from parapodial lobes (Figs 7 F–H; 8H). Pygidium semicircular, with two articulated anal cirri approximately as long as posterior dorsal cirri (not considering cirri of growth region). Pharynx thinner than proventricle (Figs. 6A; 7B), through 5–5.5 segments (Table 3), with opening surrounded by 11 soft papillae (Figs 6B, D; 8B); conical pharyngeal tooth close to anterior border (Fig. 7B). Proventricle through 4–5 segments, with 21–24 rows of muscle cells (Fig. 7B; Table 3).

Variation. Branchiosyllis gonzaguinhai sp. nov. shows some variation in pigmentation: the holotype has dark brown spots on prostomium and dorsally on each side of segments, in the bases of cirrophores; in some segments there is a thin and sparse line of these dark brown spots, however, in Paratype 1 (MZUSP 3533, there is only a thin and sparse line present. In Paratype 5 (MNRJ 1983), the median antenna is originated slightly posteriorly than lateral ones. The dorsal projection on first chaetiger is slightly shorter in some specimens analyzed. We consider these variations as intraspecific.

Remarks. Branchiosyllis gonzaguinhai sp. nov. differs from all its congeners in having a pair of dorsal swollen areas close to bases of cirrophores on first chaetiger (Fig. 8A, C), however, the new species herein described resembles B. lamellifera Verril, 1900, B. pacifica Rioja, 1941, and B. tamandarensis Paresque, Fukuda & Nogueira, 2016 by having multi-lobed branchiae and only ungulae on all parapodia (Álvarez-Campos et al., 2012; Paresque et al., 2016).

Branchiosyllis tamandarensis is the most similar species to B. gonzaguinhai sp. nov. B. tamandarensis has a yellowish to orange color, whereas B. gonzaguinhai sp. nov. has dark brown spots dorsally, on each side of each segment (Table 2). Furthermore, B. tamandarensis presents wider bodies, branchiae with up to six lobes and median antenna inserted between or slightly anteriorly to anterior pair of eyes, whereas B. gonzaguinhai sp. nov. has branchiae with up to five lobes and median antenna inserted in line with the lateral ones (Table 2).

Branchiosyllis lamellifera and B. pacifica are larger and wider than B. gonzaguinhai sp. nov. (Table 2). Branchiosyllis . lamellifera and B. pacifica have multilobed branchiae with up to three and four lobes respectively, whereas B. gonzaguinhai sp. nov. has branchiae with up to five lobes (Table 2). The species also differ in the number of ungulae, with B. gonzaguinhai sp. nov. presenting comparatively more ungulae per parapodium on anterior and posterior body (Table 2). B. gonzaguinhai sp. nov. has both median and lateral antennae longer than B. pacifica, and dorsal and ventral peristomial cirri longer than B. lamelifera and B. pacifica (San Martín et al. 2013) . Finally, B. lamellifera has pharynx and proventricle larger than B. gonzaguinhai sp. nov. (Table 2).

Holotype MNRJP Paratype 1 MZUSP Paratype 2 MZUSP 3534 Paratype 3 MNRJP Paratype 4 MNRJP Paratype 5 MNRJP 1983 1912 3533 1913 1914

Number of chaetigers / 27 / 3.7 x 0.48 (incomplete) 39 / 4.5 x 0.50

Total length x width at 36 / 4.5 x 0.42 Whole body with dark

52 / 4.6 x 0.40 55 / 6.6 x 0.47 56 / 5.25 x 0.42 Whole body with dark

proventricle (mm) incomplete purple pigmentation. purple pigmentation

Mounted for SEM Length of pharynx

5 5.5 5.5 5 not visible not visible (chaetigers)

Length of proventricle

(chaetigers x number of 4 x 24 4 x 21 5 x 23 4.5 x 22 not visible not visible

muscle cell rows)

Number of articles

Median antenna 16 13 14 14 17 17

Lateral antennae 15, 13 16, 17 14, 14 13, lost lost, 14 13, 14

Dorsal peristomial cirri

25, 30 28, 29 31, 21 incomplete. 27, lost 26, 27 31, 30

(left, right)

Ventral peristomial

lost, 13 lost, 13 13, lost 15, 13 13, 13 12, 13

cirri (left, right)

Number of ungulae per

parapodium

Anterior body 4–5 4–5 4–5 4–5 4–5 4–5

Midbody 4–5 5–6 4–5 4–5 4–5 4–6

Posterior body 4–6 5-6 4–5 lost 4–5 lost

Number of aciculae per

parapodium

2 / 1–2/ 1 2 / 1–2/ 1 2 / 1–2/ 1 2 / 1–2/ lost 2 / 1–2/ 1 2 / 1–2 / lost (anterior/midbody/

posterior body)

Habitat. Species found in association with sponges. The holotype was collected in Plakortis insularis Moraes & Muricy, 2003, and the paratype 4 in Aiolochroia crassa (Hyatt, 1875) from the Fernando de Noronha Island. The paratypes 1, 2, 3 and 5, from Rocas Atoll, were “on and within sponges”, without more information about these sponges. Moraes (2011) reported both Plakortis insularis and Aiolochroia crassa from Rocas Atoll.

Distribution. South Atlantic, Brazil: states of and Pernambuco (Fernando de Noronha Island) and Rio Grande do Norte (Rocas Atoll).

Etymology. Named after Luiz Gonzaga do Nascimento Júnior (stage name Gonzaguinha), a remarkable Brazilian popular songwriter and singer (22.Sept.1945 –29.April.1991) who has amazed and inspired generations with his talent, especially for his artistic production during the last period of military dictatorship in Brazil.