Thyone pseudofusus Deichmann, 1930

Prata, Jéssica, Manso, Cynthia Lara De Castro & Christoffersen, Martin Lindsey, 2020, Dendrochirotida (Echinodermata: Holothuroidea) from the northeastern coast of Brazil, Zootaxa 4755 (3), pp. 401-453 : 423-425

Thyone pseudofusus Deichmann, 1930

( Figure 12 )

Thyone pseudofusus Deichmann, 1930: 168 , pl. XIV, figs 6–9; Deichmann 1941: 107; Deichmann 1954: 395; Clark 1933: 114; Panning 1949: 467; Domantay 1958: 197; Tommasi 1969: 12; Hendler et al. 1995: 277, figs 182k–m; Prata & Christoffersen 2017: 53, fig. 2d.

Material examined. Paraíba State, Brazil: 1 spec., 659’00”S; 3446’41”W ( UFPB.ECH-2116); 1 spec., 701’00”S; 3446’32”W ( UFPB.ECH-2114); 2 spec., 703’50”S; 3447’19”W ( UFPB.ECH-2117); 2 spec., 703’50”S; 3447’19”W ( UFPB.ECH-2118).

Type locality. Yucatan, “Albatross 2362 Station, Mexico ( Deichmann 1930).

Description. Specimen UFPB.ECH-2114. Small body, oval to slightly curved, reaching 9 mm long, 4 mm in breadth in mid-body ( Fig. 12A ). Thin skin, rough. Color brown to white, tentacles brown. Mouth and anus terminal. Tentacles 10, short, bushy, two most ventral smaller. Introvert short. Tube feet in zigzag and in double rows in the radii, some in interradii, scattered over the body, more abundant and bigger ventrally. Calcareous ring complex, with posterior processes ( Fig. 12B ). Radial plates narrow, pointed anteriorly, with posterior processes long, divided in some pieces. Interradial plates slightly narrower than the radial plates, with anterior margin pointed and rectangular posteriorly. Madreporite rounded, stone canal short. Polian vesicle single, cylindrical. Retractor muscles wide, short, about 1/3 of the body. Longitudinal muscles slender. Respiratory trees with short branches. Gonad in single tuft, tubules short, unbranched. Body wall ossicles include tables of oval disc, with four to eight holes and thick margin (140 μm long), short two-pillared spire, ending in several teeth ( Figs. 12H, K ). Tube feet include supporting tables of elongated and narrow discs with some holes (90 µm long) ( Figs. 12 I–J), supporting plates and endplate. Introvert with rosettes (60 µm long) and tables of irregular disc (120 µm long) ( Figs. 12 C–D). Tentacles include thin rods (120 µm long), some with holes at both ends ( Figs. 12E, G ) and rosettes (40 µm long) ( Figs. 12 F–G).

Morphological variations. We analyzed six specimens, the size varied from 6–9.5 mm long, 3–3.5 mm in breadth in mid-body. Small body, usually oblong. Tube feet scattered over the body, distributed in zigzag or in double rows in the radii, sometimes also in the interradii.

Geographical distribution. North Carolina, Florida, Eastern Gulf of Mexico, Venezuela, Yucatán, Panama, Colombia, Antilles and Brazil ( Pawson et al. 2010). In Brazil it is found from Paraíba to São Paulo ( Tommasi 1969, Prata & Christoffersen 2017), down to 27 m deep. This species can be found from six to 46 m deep ( Pawson et al. 2010). Our material were found between 10–15 m deep.

Remarks. Thyone pseudofusus differs from other species known for the West Atlantic, Thyone deichmannae Madsen, 1941 and Thyone pawsoni Tommasi, 1972 , by these two species having tables with thin margins and irregular disc with few to numerous holes. Thyone pseudofusus differs from Thyone crassidisca by its short spire ending in several teeth, rather than in only one. Thyone pseudofusus differs from Thyone florianoi Martins & Tavares, 2018 by oval body wall table disc with handles, margin knobbed and short spire ending in a crown of teeth. Thyone pseudofusus differs from Thyone waltinhoi Martins & Souto, 2018 by oval body wall table disc with handles, margin knobbed, and presence of rods and rosettes in the tentacles.

Ecological notes. The specimens studied were associated with rhodoliths. On the east coast of Florida Thyone pseudofusus can be found buried in calcium carbonate particles covered with a dense layer of white calcareous silt ( Pawson et al. 2010). Two specimens analyzed had eviscerated their internal structures, such as the calcareous ring with their tentacles, gonad and retractor muscles, through the introvert. Maybe this is a form of defense.

Figures

FIGURE 12. Thyone pseudofusus Deichmann, 1930, UFPB.ECH-2114. A, external view of the animal; B, calcareous ring; C–D, tables from introvert; E, rod from tentacles; F, rosette from tentacles; G, rod and rosettes from tentacles; H, tables from body wall; I–J, supporting tables from tube feet; K, table from body wall.