Branchiosyllis exilis ( Gravier, 1900 )

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 : 57-58

Branchiosyllis exilis ( Gravier, 1900)

Syllis (Typosyllis) exilis Gravier 1900: 160 , Figs 28–30.

Branchiosyllis abranchiata Hartmann-Schröder 1965 , Figs 39–42.

Syllis (Typosyllis) fuscosuturata Augener 1922: 43 .

Syllis fuscosuturata Monro, 1933: 32 , Fig. 14.

Branchiosyllis fuscosuturata ( Augener, 1922) .- Westheide 1974: 60.

Syllis (Typosyllis) plessisi Rullier, 1972: 167

Trypanosyllis uncinigera Hartmann-Schröder 1960: 86 , Figs 54–58.

Branchiosyllis uncinigera Harlock & Laubier 1966: 18 , Figs 1–3.

Material examined. Holotype ( MNHN 143 ), Djibouti, Gulf of Aden; Mediterranean Sea: 1 specimen ( MNCN 16.01 /6551), Cabo Blanco , west of Mallorca Island , Baleares Islands , 39º19’22’’N – 2º59’01’’E, 10 m deep, coll. Fauna III (229 B7), 2 July 1994; Philippines Islands: 1 specimen ( MNCN 16.01 /14323), “Popollcan”, El Nido, Palawan Island, 11º11’50’’N – 119º17’06’’E, coral rubble, 3 m deep, “South Intalula”, El Nido, Palawan Island, 11º08'01"N – 119º19'02"E, sandy bottom, 5 m deep, 15 December 2010; 4 specimens ( MNCN 16.01 /14324), Twin Rocks, El Nido, Palawan Island, 11º15’24’’N – 119º41’41’’E, coral rubble, 6 m deep, 17 December 2010. West Australia: 4 specimens, ( AM W30095), Kimberley region , Bernouli Island , 15°S – 124°47'E, sandy substrate with coral rubble, intertidal, 12 July 1988; 1 specimen ( AM W30099), SW corner of Lucas Island , 15°13'S – 124°31'E, dead coral substrate, 2–30 m, 24 July 1988; 10 specimens ( AM W30101), inshore reef off Neds Camp, Cape Range National Park , 21°59'S – 113°59'E, Caulerpa sp. , 1 m deep, coll. J.K. Lowry, 2 January 1984; 1 specimen ( AM W33390), Monkey Mia , Shark Bay , 25º48’00’’S – 113º45’41’’E, unidentified sponges, 1 m deep, 17 June 2008; 1 specimen, Ningaloo St. , 20, 22º50’40’’S – 113º46’09’’E, coral rubble, 5.2 m deep, 14 June 2008. West Panamá, Coiba National Park : 1 specimen ( MNCN 16.01 /11542), Islote Santa Cruz , 7º38'00'' N – 81º47'20'' W, 16 m deep, 7 February 1997; 1 specimen ( MNCN 16.01 /11583), Playa Rosario , 7º38'30'' N – 81º41'40''W, coral rubble, 2.5 m deep, 16 November 1997; 1 specimen ( MNCN 16.01 /11584), Isla del Canal de Afuera , 7º41'50'' N –81º38'25'', coral rubble, 4.5 m deep, 15 November 1997; 7 specimens ( MNCN 16.01 /11587), Isla de Uvas , 7º49'00''N – 81º46'00”W, coral rubble, 3 m deep, 6 February , 1997; 1 specimen ( MNCN 16.01 /11726), Playa Rosario , 7º38'30''N – 81º41'40''W, coral rubble, 1.2 m deep, 10 September 1998; 2 specimens ( MNCN 16.01 /11727), Isla de Granito de Oro , 7º37'50'' N – 81º44'30''W, coral rubble, 2 m deep, 6 September 1997; 2 specimens ( MNCN 16.01 /11728), Isla Jicarita , 7º37'50''N – 81º44'30''W, 12 m deep, 9 February 1997; 1 specimen ( MNCN 16.01 /11733), Ensenada María , 7º24'20''N – 81º41'00''W, algae, 4 m deep, 23 June 1996; 1 specimen ( MNCN 16.01 /11734), Isla de Granito de Oro , 7º35'30'' N – 81º42'20''W, algae, 3 m deep, 20 June 1996; 4 specimens ( MNCN 16.01 /11735), Isla de Uvas , 7º49'00''N – 81º46'00''W, coral rubble, 6 m deep, 6 February 1997; 1 specimen ( MNCN 16.01 /11736), Ensenada María , 7º24'20''N – 81º41'00''W, coral rubble, 4 m deep, 23 June 1996; 12 specimens ( MNCN 16.01 /11739), Isla de Uvas , 7º49'00'' N – 81º46'00'' W, coral rubble, 3 m deep, 6 February 1997; 1 specimen ( MNCN 16.01 /11740), Isla del Canal de Afuera , 7º41'50''N – 81º38'25''W, coral rubble, 6 m deep, 12 February 1997; 6 specimen ( MNCN 16.01 / 11741), Ensenada María , 7º24'20''N – 81º41'00''W, coral rubble, 3 m deep, 14 February 1997; 1specimen ( MNCN 16.01 /11743), Islote Santa Cruz, 7º38'00''N – 81º47'20''W, coral rubble, 14 m deep, 6 February, 1997. Caribbean Sea, Cuba: 10 specimens, (16.01/751) Cayo Matías, isla de Pinos, archipiélago de los Canarreos, 21º34’28’’N – 82º26’01’’W, Halimeda sp. , 3m deep, 1990.

Comparative material. Syllis (Typosyllis) plessisi Rullier, 1972 ( Branchiosyllis plessisi sensu Westheide, 1974 ), Holotype, ( MNHN IRFA SYL Y14 ) coll. Rullier, New Caledonia, Pins Island , coral, 15 m deep, 21 August 1961.

Description. Body slender, cylindrical, variable in pigmentation (i.e. colourless, complety reddish to orange or with black lines in some parapodia). Prostomium rounded with four eyes in open trapezoidal arrangement. Median antenna longer than combined length of prostomium and palps, inserted between anterior eyes; lateral antennae inserted on anterior margin of prostomium, shorter than median antenna. Palps similar in length to prostomium. Dorsal tentacular cirri similar in length to median antenna, ventral ones shorter than dorsal tentacular cirri. Dorsal cirri similar in length or longer than total body width. Parapodial lobes distally bilobed. Compound bidentate chaetae on anterior and midbody parapodia; blades with spines on margin and shafts with distal spines. In posterior chaetigers, falcigers become unidentate with curved tips and distally curved shafts with small spines; most ventral chaetae present the ungulae rotated 180º, with short, smooth shafts. Four anterior aciculae, three straight, pointed, and one distally curving; only two aciculae on posterior parapodia, one straight and the other one slightly oblique at tip, protruding from parapodia. Pharynx through about six to eight segments; pharyngeal tooth located anteriorly, surrounded by crown of ten soft papillae. Proventricle longer than pharynx, through nine segments. Pygidium small with two anal cirri similar in shape and length to dorsal cirri.

Remarks. Although there are many small differences among the Branchiosyllis exilis specimens from different localities, all them have anterior compound falcigers and posterior ungulae but no other particular feature, such as branchiae (e.g., B. lamellifera , B. oculata , B. pacifica ) or distinct ungulae in all parapodia (e.g., B. baringabooreen , B. carmenroldanae ) (Table 1). All these small differences among the studied specimens, though not clear enough to be considered as diagnostic of different taxa may suggest that there are several sibling species traditionally named as Branchiosyllis exilis . Future molecular studies may be able to validate this hypothesis or, by contrast, confirm that it is a unique species with an intraspecific variability associated with different geographical regions. In the meantime, the small morphological differences found during the study of a large amount of material from diverse geographical areas allow us to tentatively join them into two groups. On the one hand, revised specimens from Cuba, Australia and Panamá have slender and large (longer than the total body width, 30–40 articles) cirri, and are similar with those reported from the Galapagos Islands by Westheide (1974) and from Indonesia by Aguado et al. (2008). On the other hand, specimens from the Mediterranean Sea and Philippines Islands have cirri with 15–25 articles (this paper, San Martín 2003). In addition, the anterior chaetael falcigers (i.e. on segments before proventricle) show a dorso-ventral gradation in falciger length in the specimens from the Mediterranean Sea, Cuba, Australia, and the holotype. These specimens also have bidentate blades, the dorsal ones with distal tooth equal or slightly larger than proximal one, and the ventral ones with a distal tooth much larger than the proximal one (in agreement with Aguado et al. 2008 for Indonesian material). The specimens from Panamá and Philippines Islands have bidentate falcigers similar in length, with distal and proximal teeth equal in size. Other features, such as the first segment with ungulae, the body length, and the colour pattern (often not well preserved) are highly variable and thus not useful to discriminate material (Table 1). The holotype of Syllis (Typosyllis) plessisi Rullier, 1972 , from New Caledonia, considered as a synonym of B. exilis ( Westheide 1974, Licher 1999; San Martín et al. 2008) has also been examined. Although the slide is in poor condition, the specimen agrees with Australian specimens and belongs to the group with large and slender dorsal cirri and chaetae with dorso-ventral gradation in falciger length. The specimens do not present the bidentate ungulae drawn by Rullier (1972) in anterior segments.

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

Distribution. Apparently circumtropical, also present in the warmest waters of the Mediterranean.