Thyonidium seguroensis ( 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 : 403-405

Thyonidium seguroensis ( Deichmann, 1930)

( Figure 1 )

Phyllophorus seguroensis Deichmann, 1930: 141 , pl. XVII, figs 10–13. Euthyonidium seguroensis: Deichmann 1938: 379–380 . Phyllophorus aparecidae: Ancona Lopez 1962: 122–124 , figs 4–8; Brites et al. 2006: 314. Duasmodactyla seguroensis: Heding & Panning 1954: 63 , fig. 15; Tommasi 1969: 9; Mondin 1973: 8, fig. 9; Hendler et al.

1995: 259, figs 178a–b; Prata Oliveira et al. 2010: 12–13, fig. 5b; Miranda et al. 2012: 141; Miranda et al. 2015: 116, figs

5c–d. Thyonidium seguroensis: Hansen & McKenzie 1991: 102 ; Prata & Christoffersen 2017: 49–51, fig. 1f.

Material examined. Paraíba State, Brazil: 5 spec., 7°03’48”S; 34°45’10”W ( UFPB.ECH-2101); 1 spec., Camaratuba inlet, Mataraca ( UFPB.ECH-2102); 2 spec., 7°03’50”S; 34°47’19”W ( UFPB.ECH-2103); 1 spec., 7°04’24.4”S; 34°47’49”W ( UFPB.ECH-2104); 3 spec., 07°04’5”S; 34°49’37”W, Paraíba, Brazil ( UFPB.ECH- 2065); 1 spec., 7°05’01”S; 34°47’56”W ( UFPB.ECH-2066); 1 spec., Areia Vermelha Reef, Cabedelo ( UFPB.ECH- 1217); 2 spec., Seixas Reef, João Pessoa ( UFPB.ECH-2055); 2 spec., 07°03’51”S; 34°49’51”W ( UFPB.ECH-2050); 1 spec., Picãozinho Reef, João Pessoa ( UFPB.ECH-2151); 1 spec., 7°03’48”S; 34°45’W ( UFPB.ECH-2046); 2 spec., 07°05’05”S; 34°44’21”W ( UFPB.ECH-2047); 1 spec., 07º04’26”S; 34°49′25”W, Bessa Beach, João Pessoa

( UFPB.ECH-2017); 1 spec., Tambaú Beach, João Pessoa ( UFPB.ECH-1988); 1 spec., Seixas Reef, João Pessoa ( UFPB.ECH-1997); 1 spec., Cabo Branco reefs, João Pessoa ( UFPB.ECH-1553), 2 spec. ( UFPB.ECH-1551); 1 spec., Ponta do Cabo Branco, João Pessoa ( UFPB.ECH-1680); 2 spec., Ponta do Seixas, João Pessoa ( UFPB.ECH- 874); 2 spec., Pitimbú Beach, Pitimbú ( UFPB.ECH-2040). Pernambuco State, Brazil: 18 spec., Itarema Beach, Cabo ( UFPB.ECH-2060). Alagoas State, Brazil: 1 spec., Ponta Verde reef, Maceió (EQMN-1757); 1 spec., Japaratinga Beach , Japaratinga ( UFPB.ECH-1999). Bahia State, Brazil: 4 spec., Ponta de Aratuba, Itaparica ( UFPB.ECH- 2100); 2 spec., Itapoã Beach, Salvador ( UFPB.ECH-2062).

Type locality. Porto Seguro, Bahia, Brazil ( Deichmann 1930).

Description. Specimen UFPB.ECH-1997. Elongated body, slightly curved and tapered in both ends, 8 cm long, and 4.5 cm in breadth at the middle of the body ( Fig. 1A ). Soft skin, color dark greenish-brown to brown, with whitish tube feet. Mouth and anus terminal. Tentacles 20, bushy, retracted, equal in size. Introvert short. Tube feet distributed in double rows in the radii, with more rows in the interradii covering the body, being more abundant ventrally. Calcareous ring simple ( Fig. 1B ), without posterior processes, radial plates bifid anteriorly, slightly notched posteriorly. Interradial plates triangular anteriorly, undulated posteriorly, overlapped by the radials. Madreporite rounded, small, stone canal short. Polian vesicle single, balloon-shaped. Retractor muscles thick. Longitudinal muscles large. Respiratory trees large, well branched. Gonads in single tuft, with numerous tubules divided twice. Body wall ossicles consist of rounded table disc with one central and about 12 marginal holes (100 μm long), and four-pillared spire ending in 15 or more teeth ( Figs. 1 H–I). Tube feet include supporting rods ( Fig. 1J ), perforated supporting plates ( Fig. 1K ) and endplate ( Fig. 1L ). Introvert with irregular plates ( Fig. 1G ) and small rosettes ( Fig. 1F ). Tentacles have irregular plates ( Fig. 1C ), small rods (Fig. D) and numerous rosettes ( Fig. 1E ).

Morphological variations. A total of 58 specimens were analyzed, the size varied from 4.5–104 mm long and 2–20 mm wide in the middle of the animal, 1.5–8.5 mm wide at anterior end, and 1.5–4 mm wide at posterior end. Some young specimens presented a light purple color, tube feet arranged in double rows in the radii, sometimes also into interradii, and body wall tables with higher pillars, being almost twice the size observed in old specimens. Adult specimens have tube feet covering the body, more abundant ventrally, tables with fewer holes and short pillars.

Geographical distribution. Gulf of Mexico, Jamaica, Puerto Rico, Venezuela and Brazil (from Paraíba to Bahia along the NE coast). Pawson et al. (2010) mention that this species was found from the littoral to 13 m deep. Here, we found it down to 15 m deep in the Paraíba State.

Remarks. Deichmann (1940) created the genus Euthyonidium , with Phyllophorus seguroensis Deichmann, 1930 as the type species. Later, Deichmann (1954) proposed Trachythyonidium to replace Euthyonidium , which became a synonym of Pentadactyla Hutton, 1878 . Therefore, Trachythyonidium became a junior synonym of Euthyonidium . In the revision of Heding & Panning (1954), Euthyonidium seguroensis was moved to Duasmodactyla Ayres, 1852 and more recently, this species was referred to Thyonidium by Hansen & McKenzie (1991), becoming Thyonidium seguroensis ( Deichmann, 1930) . Brites et al. (2006) noted that Phyllophorus aparecidae Lopez, 1962 from São Sebastião in Brazil had ossicles and calcareous ring similar to T. seguroensis , and suggested synonymizing this species with T. seguroensis ( Deichmann, 1930) . We do not examined Phyllophorus aparecidae to confirm this synonymy.

Ecological notes. Thyonidium seguroensis was found associated with rhodoliths, Sargassum sp., Gracilaria sp., and in phytal of Lobophora variegata and Hypnea sp. Also found in sand, sandstone, and coralline stones ( Hendler et al. 1995). Young specimens usually were found on algae.

Figures

FIGURE 1. Thyonidium seguroensis (Deichmann, 1930), UFPB.ECH-1997.A, external view of the animal; B, calcareous ring; C, plates from tentacles; D, rods from tentacles; E, rosettes from tentacles; F, rosettes from introvert; G, plate from introvert; H–I, tables from body wall; J, supporting rods from tube feet; K, supporting plate from tube feet; L, endplate.