Paraopisthosyllis correiae, Paresque, Karla, Martín, Guillermo San, Álvarez-Campos, Patricia, Nogueira, João Miguel De Matos & Fukuda, Marcelo Veronesi, 2016

Paresque, Karla, Martín, Guillermo San, Álvarez-Campos, Patricia, Nogueira, João Miguel De Matos & Fukuda, Marcelo Veronesi, 2016, Two new species and new records of the genus Paraopisthosyllis Hartmann-Schröder, 1991 (Annelida: Syllidae) from northeastern Brazil and Philippine Islands, Zootaxa 4178 (1), pp. 116-130 : 124-128

Paraopisthosyllis correiae sp. nov.

Figures 4–6 ; Table 1

Material examined. BRAZIL: State of Pernambuco: São José da Coroa Grande, Recifes São José da Coroa Grande (8°53'47''S 35°8'14''W), intertidal, coll. 25 June 2013, Holotype and Paratype ( MZUSP 2962 and 2963 respectively).

Description. Medium-sized body, largest specimen analyzed (holotype) 6 mm long, 0.7 mm wide, with 43 segments. Conspicuous pigmentation on living animals, one large transverse red stripe per chaetiger, across dorsum, between dorsal cirri, thinner posteriorly ( Figs 4 A–C, 5A); some anterior chaetigers additionally with an inverted V anteriorly and a V posteriorly ( Figs 4 A; 5A). Dorsal and ventral surfaces and dorsal appendages with papillae, more numerous on anterior dorsal cirri ( Figs 4 C, E; 5A), absent on palps and prostomium. Segments with inconspicuous secondary annulation ( Fig. 5 A). Palps rectangular, basally fused, ventrally bent in paratype. Prostomium sub-quadrangular to ovate, with red, curved line posterior to each of posterior eye ( Fig. 4 C); two pairs of eyes in rectangular to trapezoidal arrangement, anterior eyespots absent ( Fig. 5 A); antennae reddish in live specimens ( Fig. 4 A), brownish in preserved material ( Fig. 4 C); lateral antennae inserted on anterior margin of prostomium, reaching tip of palps; median antenna thicker, inserted slightly posteriorly, almost transversely aligned with anterior eyes, slightly longer than lateral antennae ( Figs 4 C; 5A); nuchal organs not visible. Peristomium dorsally short, with a transverse brown stripe ( Fig. 4 B–C); dorsal peristomial cirri brown, as long as median antenna, ventral peristomial cirri similar to dorsal ones, but slightly shorter and thinner ( Figs 4 A–C; 5A). Brown dorsal cirri throughout, those of chaetigers 1 and 4 thick, club-shaped, longer than antennae and than body width at chaetiger 1 ( Figs 4 A–C; 5A); dorsal cirri of chaetigers 2 and 5 short, digitiform, as long as ventral peristomial cirri, ca. 1/3 of body width; dorsal cirri of chaetigers 3 and 6 slightly club-shaped, slender, longer than body width; midbody dorsal cirri alternating elongated and thick cirri, club-shaped, slightly longer than body width, and short and thin cirri, about 2/3 of body width ( Figs 4 A–B; 5A); posterior dorsal cirri digitiform to club-shaped, slightly longer than body width ( Fig. 4 A). Antennae, peristomial and dorsal cirri throughout with short cirrophores ( Fig. 5 A). Ventral cirri ovate, slightly shorter than parapodial lobes. Parapodial lobes distally bilobed. Anterior parapodia with 15–24 falcigers each, midbody with 14–19, posterior parapodia with 2–12 falcigers each; shafts of falcigers subdistally spinulated, with straight tips ( Fig. 6 A–C); blades of falcigers faintly spinulated, bidentate, teeth about same size, directed forwards ( Fig. 6 A–C); blades with dorso-ventral gradation in length, 30–15 µm long on anterior chaetigers, 28–11 µm long on midbody, 15–10 µm long on posterior chaetigers. Dorsal simple chaetae from chaetigers 20–40, thin, about half width of falciger shafts, slightly sigmoid, with button-shaped tip ( Fig. 5 E); ventral simple chaetae present only on last chaetigers, slightly thinner than shafts of falcigers, sigmoid, bidentate, teeth similar in length, subdistal tooth triangular, with inconspicuous subdistal spinulation ( Figs 4 H, 5F). Anterior parapodia with 3–4 aciculae each, midbody with 2–3, posterior parapodia with single acicula each; anterior parapodia with 1–2 aciculae straight, thick, subdistally inflated, distally acuminate, and another 1–2 aciculae distally bent, with acute tips ( Fig. 5 B); midbody parapodia with one acicula subdistally bent at 90°, with acute tip, and another straight, subdistally inflated ( Fig. 5 C); posterior parapodia with only one acicula subdistally bent at 90°, with acute tip ( Fig. 5 D). Pygidium squared, anal cirri ovate ( Fig. 4 F); dorsal anus. Pharynx through three segments, with tooth slightly away from anterior border ( Fig. 4 C–D); proventricle through 2–2.5 segments, with ca. 18 muscle cell rows.

Reproduction. Schizogamy by scissiparity. Holotype (31 chaetigers) developing a posterior stolon with a pair of red eyes and 12 chaetigers; antennae not observed in stolon ( Fig. 4 G).

Remarks. Paraopisthosyllis correiae sp. nov. is the tenth known species of the genus and the first occurring in the southern Atlantic. It is characterized by its unique color pattern and by having poorly marked secondary annulation in segments, small papillae on body, large, distinct papillae on dorsal cirri, compound chaetae with elongated, bidentate blades, shafts with moderate subdistal serration on margin, and pharyngeal tooth located on the anterior third of the pharynx.

The new species most closely resembles the recently described P. pardus , from Queensland, Australia (Aguado & Glasby 2015). The specimen of P. pardus from the Philippines is 3.3 mm long, incomplete, with 16 chaetigers, and it agrees perfectly with the original description, including the characteristic color pattern. Both species have secondarily annulated segments, although not very distinct, papillated, club-shaped dorsal cirri, and similar aciculae and falcigers, although those of P. correi ae sp. nov. have shafts subdistally serrated. They differ especially in the color pattern, very characteristic in both species, and in the size of the papillae on dorsal cirri, distinctly larger in P. correiae sp. nov.

Besides P. pardus and P. c o r rei ae sp. nov., the only species with papillated dorsal cirri is P. alternocirra , which differs by having dorsal cirri with dark spots, short falciger blades, ventral simple chaetae unidentate and aciculae distally rounded.

Molecular analyses revealed Paraopisthosyllis as closely related to Megasyllis and Alcyonosyllis (Aguado et al. 2012, 2014, 2015; Aguado & Glasby 2015), which also share some morphological characters such as the almost identical compound chaetae in some species of each of these genera (Aguado & Glasby 2015) and the geographic distributions, which are restricted to shallow tropical waters. All known species of Alcyonosyllis occur in the Indo- Pacific Ocean, while those of Megasyllis and Paraopisthosyllis mostly occur in the Pacific Ocean. They are especially present in Australia, but are also found in the Western tropical and subtropical Atlantic (one species of Megasyllis and two species of Paraopisthosyllis ). The closure of the Panamá Isthmus is relatively recent in geological terms (3.2–3.5 millions of years), so it has been suggested that the spreading out of species of Megasyllis and Paraopisthosyllis into the tropical Atlantic Ocean would have been possible through this way (San Martín et al. 2014). Further studies can provide more data on these two genera.

Distribution. Atlantic Ocean: only know from off the southern coast of the state of Pernambuco, northeastern Brazil.

Etymology. The epithet ‘ correiae ’ is attributed to this species in honour of Dr Mônica Dorigo Correia (Universidade Federal de Alagoas, Brazil), who passed away recently, a devoted researcher who has contributed to great advances in the conservation of Brazilian marine habitats.

Figures

FIGURE 4. Paraopisthosyllis correiae sp. nov. (A) (B) holotype and paratype, respectively, entire worms alive; (C) holotype, anterior end, dorsal view; (D) pharynx, dorsal view; (E) detail of dorsal cirri 3 and 4; (F) posterior end, dorsal view; (G) detail of the stolon head in formation, between chaetigers 32 – 44; (H) ventral simple chaeta. Scale bars: A, C = 2 mm; B = 1 mm; D = 0.1 mm; E = 0.5 mm; F, G = 0.3 mm; H = 10 µm.

FIGURE 5. Paraopisthosyllis correiae sp. nov. (A) anterior end, dorsal view; (B – D) aciculae, anterior, midbody and posterior parapodia, respectively; (E) dorsal simple chaeta, with detail of tip; (F) ventral simple chaeta. Scale bars: A = 0.1 mm; B – F = 10 µm.

FIGURE 6. Paraopisthosyllis correiae sp. nov. (A – C) falcigers, anterior, midbody and posterior parapodia, respectively. Scale bar: A – C = 15 µm.