Holothuria (Thymiosycia) arenicola Semper, 1868

Figure 2, Table 1

Holothuria (Sporadipus) arenicola Semper, 1868: 88 .

Holothuria arenicola .― Théel, 1886: 222; Deichmann, 1926: 13 –14; 1930: 66–68; 1954: 393; H. L. Clark, 1933: 102; Cherbonnier, 1951: 30; Caso, 1955: 513.

Holothuria (Holothuria) arenicola .― Panning, 1935: 88.

Brandothuria arenicola .― Fontaine, 1953: 30; Deichmann, 1958: 290 –293; 1963: 109; Tommasi, 1969: 6.

Holothuria (Thymiosycia) arenicola .― Rowe, 1969: 145 –147; Hendler et al., 1995: 297; Laguarda-Figueras et al., 2001: 23 –25; Gondim et al., 2008: 134, Miranda et al., 2012: 141.

Material examined. Tubarão River, Diogo Lopes, Macau, RN, Brazil, 1 spec. (UFPB.ECH-1928); Búzios Beach, Nísia Floresta, RN, Brazil, 1 spec. (UFPB.ECH-2135); 1 spec. (UFPB.ECH-2140); Cabo Branco Beach, João Pessoa, PB, Brazil, 1 spec. (UFPB.ECH-1480); 1 spec. (UFPB.ECH-697); 1 spec. (UFPB.ECH-1062); Rocky shore between Gaibú and Santo Agostinho Beaches, Cabo, PE, Brazil, 1 spec. (UFPB.ECH-2143); Japaratinga Beach, Japaratinga, AL, 1 spec. (UFPB.ECH-1983); Aratuba Point, Itaparica, BA, Brazil, 2 spec. (UFPB.ECH- 2131); Pedrão, Itaparica, BA, Brazil, 2 spec. (UFPB.ECH-2132); Penha Beach, Vera Cruz, Itaparica Island, BA, Brazil, 3 spec. (UFPB.ECH-2136); Coroa Vermelha Point, Santa Cruz de Cabralia, BA, Brazil, 2 spec. (UFPB.ECH-2142).

Type locality. Lighthouse Reef, Puerto Rico (Laguarda-Figueras et al. 2001).

Diagnosis. See Deichmann (1958: 291–292).

Description. 17 specimens, preserved, measuring 40–330 mm long and up to 56 mm wide. Body elongate, sub-cylindrical, slightly flattened ventrally, more evident in bigger specimens, tegument somewhat thick (Fig. 2 A–B). Ventral mouth with 20 peltate tentacles. Small papillae laterally; tube feet ventral in 4 series of three to four rows in the radii, two rows in small specimens. Anus ventral, anal papillae not observed. Body color light brown with dark red brown or gray spots. These spots give a ferruginous aspect to the animals. In a specimen the ends are dark. Calcareous ring simple, robust (Fig. 2 C), radial plates squared-shaped, 2 mm high and wide, with central notches; interradial plates triangular-shaped, about 1 mm in height and wide, with base slightly undulated, united beyond middle of plate. Longitudinal muscles well developed, not divided. Cuvierian organs present. Body wall with tables of 4 pillars, disc rounded, about 70 µm in diameter and 30–50 µm high, with 4 larger central and about 9 smaller marginal holes (Fig. 2 E). Other tables with concave base, with 4 large central and 4 smaller marginal holes, measuring about 60 µm in diameter and 40 µm in height (Fig. 2 D). Regular buttons with 6 or more holes arranged into two rows, 100 µm long and 20–30 µm wide (Fig. 2 F). Perforated rods wider in middle, 90–180 µm long and 20–40 µm wide (Fig. 2 G). Tube feet with endplate about 200 µm in diameter (Fig. 2 H). Tentacles with simple rods, bigger in the peduncle and with little lateral rugosity, 60–245 µm long. Dorsal ossicles slightly smaller than ventral ossicles (Tab. 1).

Geographical distribution. Circuntropical species, in West Atlantic (Hendler et al. 1995), from Florida to Brazil (Ceará, Rio Grande do Norte, Paraíba, Pernambuco, Alagoas, Bahia), up to 0.3 m.

Comments. Holothuria (Thymiosycia) arenicola is a circumtropical species (Hendler et al. 1995), which was originally described from the Philippines by Semper (1868). This holothurian is usually found burrowing and is common in tropical regions of the world (Pawson & Miller 1987). It differs from Holothuria (Thymiosycia) impatiens (Forskal, 1775) and Holothuria (Thymiosycia) thomasi Pawson & Caycedo, 1980 in the Western Atlantic by the small, frequently reduced ossicles (Rowe 1969). Cutress (1996) describes the changes affecting the external morphology and shape of the ossicles during the growth of the animal. He noted a slight increase of the perforated rods with growth, as well in the number of buttons. According to Samyn et al. (2006 b), H. (T.) arenicola reported for the Caribbean can be a complex of species. Therefore, a taxonomic revision of this taxon is needed.

Ecological note. Studied specimens were found in sand and sand/mud, coral stones and corals in mangroves. In sand/mud one commonly finds this species buried.