Branchiosyllis australis, Álvarez-Campos & Martín & Aguado, 2012

Álvarez-Campos, Patricia, Martín, Guillermo San & Aguado, M. Teresa, 2012, The genus Branchiosyllis Ehlers, 1887 from Philippines Islands, with the description of two new species, Zootaxa 3542, pp. 49-68 : 55

Branchiosyllis australis n. comb. ( Hartmann-Schröder, 1981)

Figs 1A, C, E

Branchiosyllis pacifica australis Hartmann-Schröder 1981: 23 , Figs 14–18.

Branchiosyllis oculata Non Ehlers, 1887 , San Martín, Hutchings and Aguado 2008: 134, Figs 12A–E, 13C–F, 15A.

Material examined. 6 specimens (1 mounted for SEM). Luzón Island, Balayan Bay: 2 specimens ( MNCN 16.01/ 14319), “Koala Point”, 13º41'51"N – 120º49'45"E, Thalysias sp. , Acanthella sp. , 5–16 m, coral rubble, 1–2 m deep, 5 December 2010; 2 specimens ( MNCN 16.01/14320), Sombrero Island, 13º41’52’’N – 120º49’47’’E, coral rubble, 17 m deep, 6 December 2010; 1 specimen,“Beatrice Point”, Sombrero Island, two different unidentified sponges, 5–24 m, 9 December 2010. Palawan Island, El Nido: 2 specimens ( MNCN 16.01/14321),”Twin Rocks”, 11º17'50"N – 119º19'06"E, coral rubble, 6 m deep, 17 December, 2010.

Comparative material. Branchiosyllis pacifica, Coiba National Park, Chiquirí Gulf, West Panamá: 1 specimen ( MNCN 16.01 /11585), Uvas Island , 7º49'00'' N – 81º46'00'' W, coral rubble, 3 m deep, 6 February 1997 ; 5 specimens ( MNCN 16.01 /11586), Canal de Afuera Island , 7º41'50'' N – 81º38'25'' W, coral rubble, 6 m deep, 12 February 1997 ; 1 specimen ( MNCN 16.01 /11588), Uvas Island , 7º49'00'' N – 81º46'00'' W, coral rubble, 3 m deep, 6 February 1997 ; 1 specimen ( MNCN 16.01 /1706), Granito de Oro Island , 7º35'30'' N – 81º42'20'' W, coral rubble, 4.5 m deep, 19 November 1997 ; 1 specimen ( MNCN 16.01 /11710), Uvas Island , coral rubble, 16 m deep, 7 February 1997 ; 1 specimen ( MNCN 16.01 /11725), Jicarita Island , Gulf of Chiriquí, 7º37'50'' N – 81º44'30'' W, 12 m deep, 9 February 1997 ; 1 specimen ( MNCN 16.01 /11742), Cirilo tip, 7º36'10'' N – 81º50'10'' W, 4–9 m deep, 9 February 1997 . Branchiosyllis oculata , 1 Syntype ( YPMNH 6745 ), Key West , Florida, USA. Caribbean Sea, Cuba : 12 specimens (1 mounted for SEM) ( MNCN 16.01 /752), Canal de los Vapores , Cayo Bocas de Alonso , Archipiélago de los Canarreos, 21º43’02”N – 82º28’50’’W, sponges on Rhizophora mangle roots, 0.5 m deep, April 1984 .

Description. Longest complete specimen 3 mm long, 0.5 mm wide, 38 segments. Body strongly dorsoventrally flattened, pigmented on each segment with a dark central wide band. Prostomiun ovate, slightly wider than long, with two pairs of small eyes in trapezoidal arrangement. Antennae inserted on anterior margin of prostomium; median antennae shorter than combined length of prostomium and palps, with nine articles; lateral antennae longer, with 15 articles. Palps triangular, shorter than prostomium, fused at base. Nuchal organs as two ciliated pits on the lateral basis of prostomium. Peristomium dorsally reduced. Dorsal tentacular cirri longer than median antenna with 24–30 articles, ventral tentacular cirri shorter than dorsal, with about 10–12 articles. Dorsal cirri of anterior four chaetigers longer, with about 20–27 articles. Subsequent cirri with 11–15 articles. Antennae, tentacular cirri and dorsal cirri spindle-shaped. Parapodia bilobed, prechaetal lobe larger than postchaetal. Small, incipient branchiae, with minutes pores, dorsally on each parapodia, with granular appearance under light microscope ( Fig. 1A). Ventral cirri digitiform, almost as long as parapodial lobe, proximally inserted. Typically three to four compound chaetae per parapodium, smooth, unidentate ungulae, distinctly curved, all of them with ungulae rotated 180º ( Fig. 1C, E). Ventral chaetae always larger than dorsal ones; all shafts of chaetae thick, ventral ones sligthly thicker than dorsal ( Fig. 1C). Two protruding, slender, straight aciculae, one of them slightly curved on posterior parapodia ( Fig. 1E). Pygidium with two anal cirri, 7–9 articles. Pharynx almost as wide as proventricle, through five segments with a small tooth, anteriorly located. Proventricle through eight segments, with 25–30 muscle cell rows.

Remarks. Branchiosyllis oculata from the Caribbean differs from B. australis n. comb., from Australia and Philippines, in having large and very well developed branchiae ( Fig. 1B), while they are smaller in B. australis ; less curved dorsal anterior ungulae ( Fig. 1D) and three parapodial lobes: prechaetal, postchaetal and ventral lobes ( Fig. 1F), instead of only one prechaetal lobe present in B. australis ( Fig. 1E). The Philipinnes specimens slightly differ from the Australian ones in having two aciculae (only one, thick in B. australis ), one of the posterior ones slightly curved at the tip. In both populations, however, the aciculae protruded from parapodia ( Fig. 1C; San Martín et al. 2008, Figs 13E, 15A).

Habitat. Shallow waters, on sponges, algae and coral rubble.

Distribution. Philippines Islands and North Western Australia.