Ophiothrix tommasii Santana, Manso, Almeida & Alves, 2020

Silva, Jailma Ferreira Da, Christoffersen, Martin Lindsey & Prata, Jéssica, 2025, Diversity revealed: Ophiuroidea (Echinodermata) from reef ecosystems of Tropical Southwest Atlantic with new characters, Zootaxa 5689 (1), pp. 1-57 : 46-49

Ophiothrix tommasii Santana, Manso, Almeida & Alves, 2020

Ophiothrix angulate — Alitto et al. 2019: 17–18.

Ophiothrix tommasii — Santana et al. 2020:14 , Fig 10–11 .

Material examined: Formosa Beach, Cabedelo, PB: 6°58'55.5"S 34°48'55.3"W, 1 spec. ( UFPB /ECH–2462); 6º58'38.8"S 34º48'57.4"W, 2 spec. ( UFPB /ECH–2463); 6º59'05.6"S 34º49'38.5"W, 2 spec. ( UFPB /ECH–2464). Cabo Branco Beach, João Pessoa, PB: 7°08'41.1"S 34°47'43.9"W, 1 spec. ( UFPB /ECH–2465). Tambaba Beach, Conde, PB: 7º21'59.1"S 34º47'51.4"W, 1 spec. ( UFPB /ECH–2466); 1 spec. ( UFPB /ECH–2467); 7º22'8.013"S 34°47'52.02W, 6 spec. ( UFPB /ECH–2468); 2 spec. ( UFPB /ECH–2469) .

Description: specimen UFPB/ECH–2462. Circular disc ( dd = 8.10 mm and dh = 3.10 mm), dorsally covered with scales, from which emerge abundant spines, the smaller ones are bifid or trifid, the biggest long and denticulate. In the interradial region and in the radial shield (RS) the spines have two to five denticles. Large, semicircular RS, a little longer than wide and very separated by bundles of spines ( Fig. 25A ). Ventral interradial region like dorsal. Wide bursal slits, extending to the fourth arm segment, with large genital plates at the base of the arms. Rounded madreporite ( Fig. 25B ). Jaw with oral shield slightly tapered at the proximal edge, rounded in the distal, and the laterals expanded. Large, triangular, and separated adoral shield. Spaces between each hemimandible very evident. A medial column of abbreviated tooth papillae (TPa) flanked by columns of larger TPas ( Fig. 25C ). Five Arms ( aw = 5.89 mm) about four to five times longer than the dd. Diamond-shaped dorsal arm plate (DAP) ( Figs. 25F ; 26E ); the first or second plate with a small spine positioned above the DAP. Rectangular ventral arm plate, wider than long ( Figs. 25G ; 26F ); square first ventral arm plate ( Fig. 25C ). A single small and triangular tentacle scale ( Fig. 25G ). Proximal lateral arm plate with eight to 10 arm spines, and the distal with six to eight, spines with denticulate margin forming a crown of denticles at their apex, the last spine modified into a hook ( Figs. 25F, G ; 26A, J ).

Microstructures: oral plate longer than wide, abradial muscular area well defined with rib-like branching structures, and long radial channel ( Fig. 25D ); adradial joint area with poorly defined muscle insertion area; large dorsal tentacle compartment and ventral tentacle compartment ( Fig. 25E ). Dental plate with eight tooth sockets in the proximal region, that gradually decrease in size, with protruding knobs on the sides and separated by narrow septum; also, with five others smaller smaller sockets of tooth papillae at distal lateral region of the plate ( Figs 26B, C ); teeth longer than wide, with short and smooth distal surface ( Fig. 26D ). Wide lateral arm plate, a little curved in proximal region ( Fig. 26G ); inner portion with a single large perforation placed at the end of the plate ( Fig. 26H ); outer portion with six spine articulations ( Fig. 26I ). Vertebrae zygospondylous type: vertebra dorsal view with middle portion Y-shaped, slightly deep dorsal groove ( Fig. 26K ); vertebra ventral view with wide, elongated, and deep ventral groove ( Fig. 26L ); vertebra proximal view ( Fig. 26M ) and distal view ( Fig. 26N ) with dorsal muscle area much bigger than ventral muscle area.

Intraspecific variations: In younger specimens, the disc spines are bifid or trifid, and there is a small circular depression in the center of the disc. The spine of the first dorsal arm plate (DAP), a character of the species, is usually found on only one or two arms. The lateral arm plate has only five spines, the fifth being modified into a hook. The color varies from light violet to whitish. Dorsal disc with color dark violet, middle portion of the DAP with a white line that runs along the entire arm, ventral region light violet to whitish ( Figs 25A, F ).

Taxonomic comments: the species was described with the interradial region covered by small rounded and imbricated scales, which support spines with two to six thorns in the apex, lateral arm plate occupying part of dorsal surface of the arms ( Santana et al. 2020).

Morphometric variations: a total of 16 specimens were analyzed. Bigger dd: 8.10 mm, smaller dd: 0.93 mm. Average of dd = 2.68 mm with sd = 2.25 mm, dh = 1.04 mm with sd = 0.82 mm, aw = 1.87 mm with sd = 1.79 mm and la = 8.58 mm with sd = 8.44 mm ( Table 12).

Substrate: larger specimens were collected under rhodoliths, the youngest were found associated with algae.

Bathymetric distribution: possibly found at similar depth to Ophiothrix angulata , from the intertidal zone to a depth of 540m since they were previously identified as a single species ( Santana et al. 2020). More surveys are needed to verify that its bathymetry really corresponds to that of Ophiothrix angulata .

Geographic distribution: Maranhão, Piauí, Ceará, Rio Grande do Norte, Paraíba ( Formosa, Cabo Branco and Tambaba Beaches), Pernambuco, Alagoas, Bahia, Espírito Santo, Rio de Janeiro, São Paulo, Paraná, and Santa Catarina ( Santana et al. 2020, present study).

Figures

FIGURE 10. Amphipholis januarii Ljungman, 1866 internal structures. (A–B) dental plate; (C) tooth; (D) dorsal arm plate; (E) ventral arm plate; (F–H) lateral arm plate; (I) arm spine; (J) ventral vertebra view; (K) proximal vertebra view; (L) distal vertebra view.Abbreviations: Dma: dorsal muscle area; pe: perforation; Pk: protruding knobs; S: septum; Sa: spine articulation; Ts: tooth sockets; Vg: ventral groove; Vma: ventral muscle area; Zd: zygocondyle; Zp: zygosphene. Specimen UFPB/ECH– 2482.

FIGURE 11. Amphipholis squamata (Delle Chiaje, 1828). (A–B) dorsal disc; (C) ventral disc; (D) jaw; (E) oral plate external; (F) oral plate internal; (G) dorsal arm; (H) ventral arm.Abbreviations: 2°AdShSp: secondary adoral shield spine; Abja: abradial joint area; Abma: abradial muscle area; Adja: adradial joint area; Adma: adradial muscle area; AdSh: adoral shield; AdShSp: adoral shield spine; BS: bursal slits; DAP: dorsal arm plate; DASp: dorsalmost arm spine; dTCt: dorsal tentacle compartment; IPa: infradental papillae; Mad: madreporite; OPrs: Oral plate ridge spine; Osh: oral shield; pp: primary plate; Rc: radial channel; RS: radial shield; TSc: tentacle scale; VAP: ventral arm plate; VAP-1: first ventral arm plate; VASp: ventral most arm spine; vTCt: ventral tentacle compartment. Specimen UFPB/ECH–2518.

FIGURE 25. Ophiothrix tommasii Santana, Manso, Almeida & Alves, 2020. (A) dorsal disc; (B) ventral disc; (C) jaw; (D) oral plate external; (E) oral plate internal; (F) dorsal arm; (G) ventral arm. Abbreviations: Abja: abradial joint area; Abma: abradial muscle area; Adja: adradial joint area; Adma: adradial muscle área; AdSh: adoral shield; BS: bursal slits; DAP: dorsal arm plate; DASp: dorsalmost arm spine; dTCt: dorsal tentacle compartment; Mad: madreporite; OP: oral plate; OPrs: Oral plate ridge spine; Osh: oral shield; Rc: radial channel; ribs: rib-like branching structures; RS: radial shield; TPa: tooth papillae; TSc: tentacle scale; VAP: ventral arm plate; VAP-1: first ventral arm plate; VASp: ventral most arm spine; vTCt: ventral tentacle compartment. Specimen UFPB/ECH–2462.

FIGURE 26. Ophiothrix tommasii Santana, Manso, Almeida & Alves, 2020 internal structures. (A) modified arm spine; (B–C) dental plate; (D) tooth; (E) dorsal arm plate; (F) ventral arm plate; (G–I) lateral arm plate; (J) arm spine; (K) dorsal vertebra view; (L) ventral vertebra view; (M) proximal vertebra view; (N) distal vertebra view. Abbreviations: Ddmf: dorso-distal muscular fossae; Dg: dorsal groove; Dma: dorsal muscle area; pe: perforation; Pk: protruding knobs; S: septum; Sa: spine articulation; Ts: tooth sockets; TPas: tooth papillae sockets; Vg: ventral groove; Vma: ventral muscle area; Zd: zygocondyle; Zp: zygosphene. Specimen UFPB/ECH–2462.