Stolus cognatus

Stolus cognatus (Lampert, 1885)

(Figure 8)

Semperia cognita Lampert, 1885: 67.

Semperia cognata: Lampert 1885: 251.

Cucumaria cognita: Thel 1886: 266; Panning 1949: 462.

Thyone cognita: Deichmann 1930: 169, pl. XV, figs 1–4; Deichmann 1939: 134; Tommasi 1969: 14, fig. 19; Mondin 1973: 9, fig. 1; Gondim et al. 2008: 155.

Thyoneria cognata: Deichmann 1954: 398; Deichmann 1963: 110; Tikasingh 1963: 97; Caycedo 1978: 165.

Stolus cognatus: Hendler et al. 1995: 275, figs 182d–g; Laguarda-Figueras et al. 2001: 33–34, fig. 13; Miranda et al. 2012: 141, fig. 3a; Miranda et al. 2015: 115, figs 3c–d; Oliveira Prata et al. 2010: 12; Prata et al. 2017: 7, figs 9a–f.

Material examined. Rio Grande do Norte State, Brazil: 1 spec., Búzios Beach, Nísia Floresta (UFPB.ECH- 2091); 1 spec., Cumurupim (UFPB.ECH-1074). Paraíba State, Brazil: 1 spec., Cabo Branco Beach, João Pessoa (UFPB.ECH-854); 1 spec., 703’48”S; 3445’10”W (UFPB.ECH-2092); 1 spec., 706’59”S; 3446’04”W (UFPB. ECH-2056); 1 spec., Areia Vermelha Reef, Cabedelo (UFPB.ECH-2014); 1 spec., Formosa Beach, Cabedelo (UFPB. ECH-1944); 1 spec., Reefs in front of Ponta de Campina, Poço Beach, Cabedelo (UFPB.ECH-1945); 1 spec., Cabo Branco Beach, João Pessoa (UFPB.ECH-1946); 1 spec., Cabo Branco Beach, João Pessoa (UFPB.ECH-1503), 3 spec., Cabo Branco Beach, João Pessoa (UFPB.ECH-155), 3 spec., Cabo Branco Beach, João Pessoa (UFPB.ECH- 1066), 1 spec. (UFPB.ECH-1065); 1 spec., Ponta do Seixas, João Pessoa (UFPB.ECH-1073); 1 spec., Seixas Reefs, João Pessoa (UFPB.ECH-1954); 1 spec., Barra de Camaratuba, Mataraca (UFPB.ECH-1219). Bahia State, Brazil: 1 spec., Ponta do Mut Reef, Santa Cruz de Cabrália (UFPB.ECH-1991).

Type locality. Fernando de Noronha, Pernambuco, Brazil (Lampert 1885)

Description. Specimen UFPB.ECH-1946. Curved body, with tapered ends, posterior end narrower, 3 cm long, 1 cm in breadth in mid-body. Slightly thickened skin, rough (Fig. 8A). Color light brown, tube feet yellowish to white. Mouth and anus terminal. Introvert short. Tentacles 10, bushy, small, retracted, equal size. Tube feet arranged in double rows in the radii, and about five incomplete double rows in interradii, more abundant ventrally. Calcareous ring complex, formed by small distinct plates, with long posterior processes (Fig. 8B). Radial plates have a short indentation anteriorly and long processes posteriorly. Interradial plates elongate, narrow, with posterior margin concave. Madreporite spiraled, stone canal short. Two polian vesicles, one larger than the other. Retractor muscles large. Longitudinal muscles thick. Respiratory trees with short branches, well-developed. Gonad in a single tuft, tubules divided at least once. Body wall ossicles consist of numerous elongated plates (300 µm long), with two rows of holes (Figs. 8 H–I), sometimes holes alternated; small buttons plate-shape with four sub-equal holes (90 µm long). Tube feet include thick supporting plates (170 µm long), curved, with four large central holes and few small marginal holes (Fig. 8K); supporting rods (180 µm long), some with a third arm (Fig. 8J) and endplates (150 µm long) (Fig. 8L). Papillae near the ends with numerous irregular plates. Introvert includes irregular rosettes (30 µm long) (Fig. 8F) and large thick plates (100 µm long) (Fig. 8F). Tentacles have small rods, some with holes in the ends (80 µm long) (Fig. 8D), large rods (Fig. 8E) (150 µm long) and rosettes (30 µm long) (Fig. 8C).

Morphological variations. 26 specimens were analyzed. The size varied from 12–24 mm long, 2.5–17 mm in breadth in mid-body, 1–3 mm in breadth at anterior end, and 1.5–6 mm in breadth at posterior end. Young specimens have tegument slightly thickened, usually white in color; tube feet arranged in double rows in the radii, with discreet double rows in interradii; only elongated perforated plates, with two rows of holes and large endplates in the body. The color of the specimens varied from light brown to grayish blue.

Geographical distribution. Florida, Antilles, Venezuela and Brazil (Hendler et al. 1995). In Brazil from Rio Grande do Norte to São Paulo (Tommasi 1969; present study). It was found down to 15 m deep.

Remarks. Lampert (1885) analyzed specimens of the different European museums to write his monograph, and he cites two type localities for Stolus cognatus, Cuba based on the material from the Natural History Museum, Berlin and Fernando de Noronha (Brazil) from material provided by Selenka in the Erlangen collection, Germany. Stolus cognatus is the only species of this genus reported for the Western Atlantic.

Ecological notes. The specimens analyzed were found associated with rhodoliths, reefs, inside or under rocks, sometimes near the ophiuroids Ophioderma appressa (Say, 1825) and Ophiocoma echinata (Lamarck, 1816). Specimens observed by Clark were found buried in soft bottoms, in eel grass (Deichmann 1930).