Orbinia johnsoni ( Moore, 1909 )

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 : 152-154

Orbinia johnsoni ( Moore, 1909)

Figures 6 A–C; 7 A–E

Aricia johnsoni Moore, 1909 , pp. 260–262, Pr. 8, figs. 30–33.

Orbinia johnsoni Hartman, 1944 , pp. 258–259; Solís-Weiss, 2009, p. 386, fig. 3F.

Type-locality: USA, California, Marin County.

Material examined. Total: 4 specimens. Hab. 17; FOZ 31; Repl. 03; RPS (1 spec., MNRJ /P783), 21º 40′S 40º 20″W. Depth: 47 m; Hab. 17; FOZ 19; Repl. 0 2 (1 spec., MNRJ /P782), 21º 50′S 40º 40″W. Depth: 21 m; Hab. 11; PLAT. E1; Repl. 0 1 (1 spec., MNRJ /P784), 22º 0′S 40º 40″W. Depth: 25 m; Hab. 11; PLAT. A2; Repl. 0 1 (1 spec., MNRJ /P785), 23º 20′S 42º 0″W. Depth: 50 m.

Diagnosis. Prostomium conical; 18 to 19 thoracic chaetigers. Branchiae from chaetigers 15 to 20. Lateral flange and furcate chaetae present.

Description. Three incomplete specimens, 4.5 to 8 mm in total length, 40 to 55 chaetigers. Complete specimen, 16 mm in length, 78 chaetigers. Prostomium conical and pointed ( Fig. 6 A), 0.12 mm wide and 0.12 mm high. Peristomium with one ring. Anterior thoracic region (chaetigers 1–3) 0.6 mm in length. First abdominal chaetiger 1 mm wide.

Thorax cylindrical, with 18 chaetigers. Branchiae from chaetigers 11 to 19 ( Figs. 6 B), twice as long as posterior chaetigers. Thoracic notopodial post-chaetal lobe elongate, visible from chaetiger 1 ( Fig. 7 B). Thoracic neuropodial post-chaetal lobe unique ( Fig. 7 B).

Abdomen cylindrical. Abdominal notopodial post-chaetal lobe unilobed ( Fig. 7 C), with one papillae from chaetigers 10 to 17, and two papillae on chaetiger 18. Abdominal neuropodia bilobate, dorsal lobe longer than ventral one, with lateral flange ( Fig. 6 C; 7C) and 4 papillae on first abdominal chaetigers. Thoracic notochaetae with crenulated capillaries (6–7). Abdominal notochaetae with crenulated capillaries (4–5) and furcated (1) ( Fig. 7 D). Thoracic neuropodia with 4 rows of uncinate spines and crenulated capillaries (5–7); abdominal neurochaetae with crenulated capillaries (5–6). Pygidium with one pair of cirriform anal cirri.

Occurrence. Campos Basin, Southeastern Brazil, Rio de Janeiro. Depth range: 21– 50 m.

Distribution. Pacific: California, Mexico; Atlantic: Southeastern Brazil.

Remarks. The absence of interramal cirri and the presence of 2–6 ventral papillae in the thoracic notopodia are similar to what was described by Moore 1909 for individuals from the Pacific. Our specimens show variations in the position of the first pair of branchiae, from chaetigers 11 to 19, whereas specimens described by Moore have branchiae from chaetigers 15–20. However they are similar to the material described by Solís-Weiss et al. (2009) from the Gulf of Mexico and the southern Mexican Pacific. Orbinia johnsoni differs from O. latreilli ( Audouin & Milne Edwards 1833) , described from Western France, Southwestern Italy and Southeastern Brazil, by the position of the first pair of branchiae, i.e. from chaetiger 5 in O. latreilli . Orbinia johnsoni is also similar to Orbinia hartmanae Day, 1977 , described from Australia and New Zealand, in the number of thoracic chaetigers and the presence of a subpodial lobe, but they differ in the presence of thoracic neuropodia, with a single post-chaetal lobe in O. johnsoni . The species was recorded around 21–50 m in Campos Basin, whereas records from central California to Costa Rica are from 8– 10 m. This is the first record of the species for the Brazilian coast.

Figures

FIGURE 6. Orbinia johnsoni. A: Anterior end, dorsal view. B: Branchiae (arrows), chaetigers 11 and 12. C: Bilobate abdominal neuropodia with lateral flange, chaetiger 22.

FIGURE 7. Orbinia johnsoni: A: Anterior end, dorsal view; B: Thoracic parapodium, chaetiger 15; C: Abdominal parapodium, chaetiger 20; D: Furcated notopodial chaeta, chaetiger 20; E: Abdominal neuropodial uncini, chaetiger 20.