Orbinia oligopapillata López, Cladera and San Martin, 2006

Leão, Luciana Sanches Dourado & Santos, Cinthya Simone Gomes, 2016, Orbinia (Polychaeta: Orbiniidae) from the Brazilian coast: two new species and two new records, Zootaxa 4105 (2), pp. 145-158 : 154-155

Orbinia oligopapillata López, Cladera and San Martin, 2006

Figures 8 A–B; 9 A–C

Orbinia oligopapillata López, Cladera and San Martin, 2006: 1307 –1318, figs.1–3.

Type-locality. Pacific coast of Panamá.

Material examined. Total: 6 specimens. Hab. 11; PLAT. C2; Repl. 0 2 (1 spec., MNRJ /P778), 22o 40′S 41o 20″W. Depth: 50 m; Hab. 17; PLAT. A4; Repl.1 (1 spec., MNRJ /P781), 23º 20′S 42º 0″W. Depth: 100 m; Hab. 16; PLAT. H1; Repl. 2 (1 spec., MNRJ /P779), 22º 0′S 40º 40″W. Depth: 25 m; Hab 13; FOZ 12; Repl. 02; RPS (2 spec., MNRJ /P780), 21º 40′S 40º 50″W. Depth: 22 m; Hab. 17; FOZ 21; Repl. 02; RPS (1 spec., MNRJ /P777, 21º 10′S 40º 40″W. Depth: 47 m.

Diagnosis. Prostomium conical and pointed; 16–19 thoracic chaetigers. Branchiae from chaetigers 8–10. Papillae on thorax and abdomen. Furcate chaetae absent. Flail-tipped chaetae present. Interramal cirri and subpodial lobes present.

Description. All specimens incomplete, ranging from 3.5 mm to 10 mm in total length with 20 to 59 chaetigers. Prostomium conical and pointed ( Fig. 8 A), 0.2 mm wide and 0.25 mm high. Peristomium with one ring. Anterior thoracic region (chaetigers 1–3) 0.5 mm wide. First abdominal chaetiger 0.7 mm wide.

Thorax slightly compressed dorsoventrally, subcylindrical, with 19 chaetigers. Branchiae always ligulate, from chaetiger 10 ( Fig. 9 A), twice as long in abdomen. Thoracic notopodia with one elongate post-chaetal lobe, visible from chaetiger 4 ( Fig. 9 B). Abdomen cylindrical. Abdominal notopodia with one post-chaetal lobe. Abdominal neuropodia bilobate, dorsal lobe longer than ventral one, with interramal cirri, subpodial lobe and 5 papillae on chaetigers 20 and 21 and 4 papillae on chaetiger 22.

Thoracic notochaetae with crenulated capillaries (10–15); abdominal notochaetae with crenulated capillaries (6–8). Thoracic neurochaetae with rows of smooth uncinate spines ( Fig. 8 B) accompanied by crenulated capillaries (8–10). Abdominal neurochaetae with crenulated capillaries (4–5) and flail-tipped chaetae.

Distribution. Pacific: Panama coast; Atlantic: Southeast Brazil.

Occurrence. Campos Basin, Rio de Janeiro, Southeast Brazil. Depth range: 22– 100 m.

Remarks. The number of thoracic chaetigers, position of the first pair of branchiae, the presence of interramal cirri and a subpodial lobe characterize O. oligopapillata . Among the Orbinia species described for the Brazilian coast, Orbinia latreilli ( Audouin & Milne Edwards 1833) also exhibits flail-tipped chaetae, a subpodial lobe and interramal cirri, but these two species differ in the position of the first pair of branchiae and the distribution of the papillae. Orbinia oligopapillata is also similar to Orbinia hartmanae Day, 1977 from Australia, but differs in the absence of interramal cirri and lobes in the thoracic parapodia, as observed in O. hartmanae . Another similar species is Orbinia riseri Pettibone, 1957 , described from the Atlantic (Massachusetts), which has branchiae from chaetigers 8–10, four rows of smooth thoracic uncini and interramal cirri on the abdominal neuropodia, but O. riseri lacks flail-tipped chaetae. Up to now Orbinia oligopapillata had been observed at lower depths, both in the Panamanian coast and in Campos Basin. This is the first record of O. oligopapillata from the Brazilian coast.

Figures

FIGURE 8. Orbinia oligopapillata. A: Prostomium, dorsal view. B: Neuropodial uncinate spines, chaetiger 17.

FIGURE 9. Orbinia oligopapillata. A: Anterior end, dorsal view; B: Thoracic parapodium, chaetiger 16; C: Flail-tipped neurochaeta of abdominal parapodium, chaetiger 20.