Ophiophragmus luetkeni ( Ljungman, 1872 )

Ophiophragmus luetkeni ( Ljungman, 1872) View in CoL

Amphipholis luetkeni View in CoL — Ljungman 1872: 636.

Ophiophragmus luetkeni View in CoL — Tommasi 1965: 7; 1970: 31, Fig. 28–29; 1999; Monteiro 1987: 88, Est. Ve, f; 1997: 183; Manso & Absalão 1988: 79; Manso 1991: 37; Pires-Vanin et al. 1997: 37; Neto et al. 2005: 213; Borges & Amaral 2005: 269, Fig. A–D; Borges 2006: 51, Fig. 1.15 View FIGURE 1 ; Manso et al. 2008: 193, Fig. 19f, g View FIGURE 19 ; Barboza 2010: 15; Oliveira et al. 2010:7; Alitto et al. 2016: 12, Fig.4G–H View FIGURE 4 ; Bueno et al. 2018: 215, Fig. 55; Prata et al. 2020: 6, Fig. 4a–e View FIGURE 4 .

Material examined: Barra de Mamanguape reefs, Rio Tinto, PB: 6°45'49.35"S 34°55'4.85"W, 2 spec. ( UFPB / ECH–2457). Formosa Beach, Cabedelo, PB: 6°59'9.81"S 34°49'37.64W, 2 spec. ( UFPB /ECH–2456) GoogleMaps .

Description: specimen UFPB/ECH–2456. Circular disc ( dd = 6.42 mm and dh = 1.66 mm), dorsally covered with small, circular, imbricated scales, the largest are at the center of the disc, and near the radial shield (RS), which cover the lateral edge of shields. Disc edge bordered by bundles of long, thin spines, lined up and facing upwards. Semicircular RS, longer than wide, separated at the proximal edge by one to three scales, and with an accessory plate on the distal edge ( Fig. 15A View FIGURE 15 ). Ventral interradial region covered by smaller scales that are more imbricated than the dorsal ones, and with larger scales near the jaw. Long bursal slits, with large genital scales ( Fig. 15B View FIGURE 15 ). Jaw with diamond-shaped oral shield, tapered proximal edge, and more elongated and rounded distal edge. Large and whitish madreporite ( Fig. 15B, C View FIGURE 15 ). Triangular adoral shield, with tapered ends and united in the proximal portion ( Figs 15C, F View FIGURE 15 ). Spatulate and elongated adoral shield spine, larger secondary adoral shield spine, a pair of rectangular, large, and separated infradental papillae ( Fig. 15C View FIGURE 15 ). Five arms ( aw = 1.66 mm), about six to seven times longer than the dd. Semi-rectangular dorsal arm plate, wider than long, with a rounded and sometimes fragmented distal edge ( Figs 15G View FIGURE 15 ; 16D View FIGURE 16 ). Square to pentagonal ventral arm plate ( Figs 15H View FIGURE 15 ; 16E View FIGURE 16 ); trapezoidal first ventral arm plate ( Fig. 15C View FIGURE 15 ). Two tentacle scales, well separated, arranged in parallel, forming a right angle ( Fig. 15H View FIGURE 15 ). Three arm spines, the ventral most arm spine smaller ( Figs 15G, H View FIGURE 15 ; 16I View FIGURE 16 ).

Microstructures: oral plate with abradial muscular area well defined and with rib-like branching structures, long radial channel ( Fig. 15D View FIGURE 15 ); adradial joint area with the muscular insertion area quite striated; large dorsal tentacle compartment and ventral tentacle compartment ( Fig. 15E View FIGURE 15 ). Dental plate with a rounded proximal region and a very tapered distal region; eight tooth sockets, larger proximal openings, with protruding knobs on the sides and separated by narrow septum ( Figs 16A; B View FIGURE 16 ); teeth with large smooth and flat distal surface ( Fig. 16C View FIGURE 16 ). Wide lateral arm plate, slightly curved in the proximal region ( Fig. 16F View FIGURE 16 ); inner portion with a single perforation ( Fig. 16G View FIGURE 16 ); outer portion with three spine articulations, parallel and separate ( Fig. 16H View FIGURE 16 ). Vertebrae zygospondylous type: vertebra dorsal view with a V-shaped medial portion, slightly deep dorsal groove ( Fig. 16J View FIGURE 16 ); vertebra ventral view with elongated and deep ventral groove, with the four well-defined muscular fossae ( Fig. 16K View FIGURE 16 ); vertebra proximal ( Fig. 16L View FIGURE 16 ) and distal ( Fig. 16M View FIGURE 16 ) view with dorsal muscle area bigger than ventral muscle area.

Intraspecific variations: despite the few specimens, some variations were noted in the younger individuals. They have larger dorsal scales near the radial shield (RS), being smaller in the center of the disc and more imbricated in the interradial portion, while in adults the scales tend to be smaller and flatter. In addition, in the young specimens the RS are more triangular, with a more tapered proximal edge, and separated by up to three scales. Color gray ( Figs 15A, G View FIGURE 15 ).

Taxonomic comments: oral plate with abradial muscular area well defined and with rib-like branching structures, long radial channel ( Fig. 15D View FIGURE 15 ); an adradial joint area with the muscular insertion area quite striated; large dorsal tentacle compartment and ventral tentacle compartment ( Fig. 15E View FIGURE 15 ). Dental plate with a rounded proximal region and a very tapered distal region; the species has also been described with pentagonal disc, an interradial region with indentations, radial shield separated proximally by 12 scales, and rectangular adoral shield spine ( Tommasi 1970). By trapezoidal dorsal arm plate, longer than wide, altered along the length of the arm ( Prata et al. 2020), rectangular to square ventral arm plate ( Prata et al. 2020), without projection in the distal portion ( Chagas et al. 2020). A ventral portion of the lateral arm plate more elongated and curved, a vertebra ventral view with deeper muscle fossaes, and a vertebra proximal and distal view with more large dorsal muscle area and ventral muscle area ( Chagas et al. 2020; Prata et al. 2020).

Morphometric variations: a total of four specimens were analyzed. Bigger dd: 6.42 mm, smaller dd: 4.13 mm. Average of dd = 5.41 mm with sd = 1.08 mm, dh = 1.15 mm with sd = 0.43 mm, aw = 1.38 mm with sd = 0.25 mm, and la = 39.10 mm with sd = 7.18 mm ( Table 7).

Substrate: specimens collected on a sandy bottom near the coast and in a muddy bottom, like that collected by Tommasi (1970) to a depth of 1.5 m. The species can be found in sediment classified as coarse silt or in muddy bottoms ( Chagas et al. 2020).

Bathymetric distribution: From 1 to about 50 m ( Chagas et al. 2020).

Geographic distribution: Virgin Islands, Tobago, Brazil ( Tommasi 1970). In Brazil: Paraíba in the Barra de Mamanguape reefs ( Prata et al. 2020) and Formosa Beach (present study), and Bahia ( Manso et al. 2008) to Santa Catarina ( Bueno et al. 2018).