Psolus tommasi, Martins & Tavares, 2019

Martins, Luciana & Tavares, Marcos, 2019, Two new species of Psolus Oken from Brazil (Holothuroidea: Psolidae), with neotype designation and redescription of Psolus vitoriae Tommasi, 1971, and a key to the southwestern Atlantic and Magellanic species, Zootaxa 4563 (3), pp. 531-546 : 536

Psolus tommasi sp. nov.

( Figs. 3–4 ; Table 1)

Type material. Holotype, 12 mm ( MZUSP 583 ), Brazil, off coast of São Paulo, 24°20’S, 44°09’W, REVIZEE, 10.i. 1998, 258 m.

Type Locality. São Paulo (24°20’S, 44°09’W), Brazil, 258 m.

Distribution. Known only from the type locality.

Etymology. This species is named in honour of Prof. Luís Roberto Tommasi (IOUSP), in recognition for his dedication and contributions to the taxonomy of echinoderms.

Diagnosis. Body flat ventrally, convex dorsally. Dorsum covered by multi-layered, imbricating scales devoid of granules. Five oral valves. Anus surrounded by variable number of small, irregular anal valves. Oral and anal valves distinct from body wall scales; oral teeth present (anal teeth not observed). Calcareous ring with radial plates notched, interradial plates not notched. Tube feet restricted to ventrolateral ambulacra, tube foot ossicles are perforated rods and end plates. Dorsum with spheroid bodies; venter with knobbed as well as smooth, perforated plates.

Description. Venter flat, dorsum convex, 12 mm long, 7.5 mm wide ( Fig. 3A ). Mouth surrounded by five triangular valves of equal size ( Fig. 3A, B ). Anus surrounded by variable number of small, irregular anal valves. Oral teeth present, anal teeth not observed ( Fig. 3A, B ). Body wall scales well demarcated from oral and anal valves. Dorsum lacking tube feet, covered with conspicuous, imbricating scales ( Fig. 3A, C & 4A ), devoid of granules. Scales along dorsolateral margin smaller (0.3 mm) than mid-dorsally (to 2 mm). Sole thin, without scales. Tube feet restricted to ventrolateral ambulacra in paired rows of an inner row of large tube feet, outer row of small tube feet ( Fig. 3D ). Mid-ventral tube feet row absent. Polian vesicles not observed. Ten dendritic tentacles, eight large and two small ventrally. Calcareous ring simple, lacking posterior processes; radial plate notched, interradial plate not notched ( Fig. 3E, F ). Dorsum ossicles include spheroid bodies, irregular in outline, with digitate margins (160–200 µm long), with round holes 10–20 µm in diameter ( Fig. 4B ). Sole ossicles are knobbed, perforated, single-layered plates, irregular in outline, with knobby edges (100–200 µm long) and round holes 10–25 µm in diameter ( Fig. 4C ), and curved, smooth, perforated plates (100–150 µm long), with holes up to 10–25 µm in diameter ( Fig. 4D ). Tube feet support ossicles irregular, curved, perforated rods, with undulating margins (up to 180 µm long) ( Fig. 4E ).

Remarks. Although Psolus tommasi sp. nov. is known only from the holotype, it can be distinguished from its southwestern Atlantic congeners, P. vitoriae and P. lawrencei , in having un-notched interradial plates on the calcareous ring (vs. interradial plates notched in P. vitoriae and P. lawrencei ) and from Psolus murrayi Théel, 1886 , in having no midventral tube feet, present in P. murrayi .

Psolus tommasi sp. nov. differs from P. patagonicus in possessing spheroid bodies, lacking in P. patagonicus , and in having a variable number of small, irregular anal valves instead of five, regular ones in P. patagonicus .

The spheroid bodies in the dorsum distinguish P. tommasi from P. antarcticus and P. segregatus , as these latter have single-layered, smooth plates.

Figures

FIGURE 3. (A–F) Psolus tommasi sp. nov., holotype (MZUSP 583). (A) Dorsal view. Note the oral and anal valves (black and white arrows, respectively). (B) Anal and oral regions (above and below left, respectively), and detail of anal valves and oral teeth (black arrows), above and below right. (C) Detail of the lateral scales. (D) Detail of the ambulacral feet in ventral view. Note the inner and outer rows of tube feet (black and white arrows, respectively). (E) Interradial (IR) and radial (R) plates of the calcareous ring. (F) Outline of the interradial (IR) and radial (R) plates of the calcareous ring. Note in E, F that only the radial plate is notched. Scale bars: A, 6 mm; B, 1mm; C, 0. 3 mm; D, 1 mm; E–F 500 µm.

FIGURE 4. Psolus tommasi sp. nov., holotype (MZUSP 583). SEM photomicrographs of the ossicles. (A) Dorsal scales. (B) spheroid bodies from dorsal/lateral scales. (C) Knobbed, single layered plate from sole. (D) Smooth, perforated plate from sole. (E) Rods from tube feet. Scale bars: A, 500 µm; B, 50 µm; C, 70 µm; (D) 40 µm and (E) 100 µm.