Ophiocnida scabriuscula (Lütken, 1859)

Ophiocnida scabriuscula (Lütken, 1859) View in CoL

Amphiura scabriuscula —Lütken 1859: 220–221, tab. III, Fig. 4 View FIGURE 4 .

Ophiophragmus scabriuscula —Ljungman 1867: 316.

Ophiocnida scabriuscula View in CoL — Rathbun 1879: 155; Lima-Verde 1969: 11; Tommasi 1970: 30, Fig. 26 View FIGURE 26 –27; 1999; Boffi 1972: 319; Alves & Cerqueira 2000: 545; Neto et al. 2005: 212; Borges & Amaral 2005: 268, Fig. A–D; Magalhães et al. 2005: 63; Borges 2006: 49, Fig. 1.14 View FIGURE 1 ; Gondim et al. 2008: 154; Lima & Fernandes 2009: 61; Oliveira et al. 2010: 9, Fig.3O View FIGURE 3 ; Lima et al. 2011: 8, Fig. 5E View FIGURE 5 ; Barboza & Borges 2012: 14; Miranda et al. 2012: 140; Gondim et al. 2013a: 64 View Cited Treatment , Fig. 5 View FIGURE 5 , 6 e–i View FIGURE 6 ; Souto & Martins 2017: 306; Bueno et al. 2018: 214, Fig. 54.

Material examined: Barra de Mamanguape reefs, Rio Tinto, PB: 6°45'54.0"S 34°55'04.0"W, 1 spec. ( UFPB /ECH– GoogleMaps

2453). Bessa Beach, João Pessoa, PB: 7º04'33.0"S 34º49'30.0"W, 1 spec. ( UFPB /ECH–2454). Carapibus Beach, Conde, PB: 7°17'59.0"S 34°47'54.0"W, 1 spec. ( UFPB /ECH–2452) GoogleMaps .

Description: specimen UFPB/ECH–2452. Circular disc ( dd = 9.22 mm and dh = 2.41 mm), dorsally covered by irregular, imbricate, small scales, of which the largest are close to the radial shield (RS). Tiny spines cover the entire disc, except the RS. These spines are larger and more abundant in the interradial region, some thorns have curved tips or denticles. RS longer than wide, separated, and with accessory plates on the distal edge ( Fig. 13A View FIGURE 13 ). Ventral interradial region covered by scales and spines, however, close to the jaw, only scales and rare spines. Wide bursal slits ( Fig. 13B View FIGURE 13 ). Jaw with diamond-shaped oral shield, with very tapered distal edge and rounded proximal. Evident, whitish, and rounded madreporite ( Figs 13B, C, F View FIGURE 13 ). Subtriangular adoral shield, that does not touch proximally. Large and rectangular adoral shield spine, smaller and flabelliform secondary adoral shield spine, a large and contiguous infradental papillae ( Fig. 13C View FIGURE 13 ). Five arms ( aw = 2.54 mm), about six to seven times longer than the dd. Rectangular, wider than long dorsal arm plate, overlapping ( Figs 13G View FIGURE 13 ; 14D View FIGURE 14 ). Rectangular ventral arm plate, with the distal straight and the proximal with a slight projection or pointed ( Figs 13H View FIGURE 13 ; 14E View FIGURE 14 ); smaller first ventral arm plate, with strong indentation on proximal edge ( Fig. 13C View FIGURE 13 ). Two tentacle scales perpendicular and similar in size ( Fig. 13H View FIGURE 13 ). Three, rod-shaped arm spines, the middle one slightly larger than others ( Figs 13G, H View FIGURE 13 ; 14I View FIGURE 14 ).

Microstructures: oral plate with abradial muscular area well delimited with rib-like branching structures, and radial channel long ( Fig. 13D View FIGURE 13 ); adradial joint area with muscular insertion area without evident stria; large dorsal tentacle compartment and ventral tentacle compartment ( Fig. 13E View FIGURE 13 ). Outer portion of dental plate with six tooth sockets, protruding knobs protruding on its sides and separated by narrow septum ( Fig. 14A View FIGURE 14 ); in the inner portion the plate has a large central dental cavity and some smaller cavities ( Fig. 14B View FIGURE 14 ) and large teeth, distal region with smooth surface ( Fig. 14C View FIGURE 14 ). Lateral arm plate twice as longer than wide, convex proximally ( Fig. 14F View FIGURE 14 ); inner portion without visible perforation ( Fig. 14G View FIGURE 14 ); distal margin with three and separated spine articulations ( Fig. 14H View FIGURE 14 ). Vertebrae zygospondylous type: dorsal view vertebra with middle portion V-shaped, slightly deep dorsal groove, wide and deep dorso-distal muscular fossae ( Fig. 14J View FIGURE 14 ); ventral view vertebra with elongated ventral groove, deep in the middle region, with four well defined muscle fossaes, the most proximal deeper, the distal one circular ( Fig. 14K View FIGURE 14 ); proximal ( Fig. 14L View FIGURE 14 ) and distal ( Fig. 14M View FIGURE 14 ) view vertebra with dorsal muscle area bigger than ventral muscle area.

Intraspecific variations: oral plate with an abradial muscular area well delimited with rib-like three specimens was analyzed, an adult and two young. Despite the few individuals, some variations were observed in the young stages. More imbricated and smaller dorsal scales, with more defined bands in the spines, tapered radial shield on the proximal edge, with radial shields separated almost entirely by scales, and the outarm spine slightly flattened. The color is light brown ( Figs 13A, G View FIGURE 13 ).

Taxonomic comments: the species were also described with the disc scales, in the central and interradial region, covered by a tegument, with three oral papillae and two arm spine ( Tommasi 1970), however, Gondim et al. (2013a Fig. 6H View FIGURE 6 ) does not describe the presence of this tegument and mention only two oral papillae. The present material corroborates with the latter.

Morphometric variations: a total of three specimens were analyzed. Bigger dd: 9.22 mm, smaller dd: 5.62 mm. Average of dd = 7.07 mm with sd = 1.90 mm, dh = 2.13 mm with sd = 0.27 mm, aw = 2.39 mm with sd = 0.33 mm, and la = 42.42 mm with sd = 11.40 mm ( Table 6).

Substrate: specimens were collected under rocks and associated with sponges. They can also be found on sandy bottoms ( Tommasi 1970), rock crevices ( Alves & Cerqueira 2000) and in marine phanerogams ( Hendler et al. 1995).

Bathymetric distribution: from the intertidal zone to about 30 m ( Tommasi 1970; Gondim et al. 2013b).

Geographic distribution: Florida ( Tommasi 1970), Bermuda, Dry Tortugas, Jamaica, Puerto Rico, Virgin Islands, Tobago, Venezuela, Brazil ( Hendler et al. 1995). In Brasil: Ceará ( Lima-Verde 1969), Rio grande do Norte ( Lima-Verde 1969), Paraíba in Cabo Branco Beach ( Gondim et al. 2008; 2013a), Carapibus Beach, and Barra de Mamanguape reefs (present study), Pernambuco ( Lima & Fernandes 2009), Alagoas ( Lima et al. 2011; Miranda et al. 2012) and Bahia ( Alves & Cerqueira 2000; Magalhães et al. 2005; Souto & Martins 2017).