Thyonella gemmata ( Pourtalès, 1851 )

Martins, Luciana, 2018, Taxonomy of the genus Thyonella (Holothuroidea: Dendrochirotida), with mention of the first record of T. sabanillaensis from the southwestern Atlantic Ocean, Zootaxa 4527 (1), pp. 75-86 : 81-82

Thyonella gemmata ( Pourtalès, 1851)

( Figs. 5–6 )

Colochirus gemmatus Pourtalès, 1851: 11

Thyone gemmata— Théel, 1886: 138

Thyonella gemmata— Verril, 1872: 437

Thyone gemmata— Deichmann, 1930: 177 –178, pl. 17, figs. 1–3

Thyonella gemmata— Deichmann, 1954: 398

Thyonella gemmata— Miller & Pawson, 1984: 20 –23, fig. 13

Thyonella gemmata— Hendler et al, 1995: 263 –264, figs. 143, 179 A–D.

Material examined. Bahamas, Long Island, 15.viii.1975, depth 1m, 1 spm, 30 mm ( CASIZ 104737 ) .

Type locality. Sullivan Island , South Carolina ( Pourtalès, 1851) .

Distribution. From Massachusetts to Florida, Gulf of Mexico, Cuba, Yucatàn Peninsula. Bathymetric range: currently known to inhabit muddy or sandy areas, often associated with seagrasses ( Miller & Pawson, 1984). Depth ranging from the intertidal to 20 m ( Hendler et al., 1995).

Diagnosis. Calcareous ring lacking posterior processes. Tube feet distributed along the ambulacra in two rows and scattered in the interambulacra. Body wall ossicles include deep four-holed cups, four-holed knobbed buttons and smooth plates. Introvert ossicles comprise rosettes and plates, tentacles with rods.

Description. Body U-shaped, when fixed assumes a barrel-shaped ( Fig. 5A ). Color in ethanol brown. Tube feet distributed along the ambulacra in two rows and scattered in the interambulacra. Anal papillae present. Interradial plate narrows anteriorly, lacking posterior process ( Fig. 5B ), retractor muscle flat ( Fig. 5B ).

Body wall ossicles comprise four-holed cups deep (40–50 µm long, Fig. 6 A–C); four-holed buttons, flat and with low knobs (80–150 µm long, Fig. 6 D–E). According to Hendler et al. (1995), in both anterior and posterior ends with smooth to knobbed perforated plates. Introvert with perforated plate (80–100 µm long, Fig. 6F ) and small rosettes (25–40 µm long, Fig. 6G ). The tentacles with two types of perforated rods present: i) flattened and irregular in outline (150–200 µm long, Fig. 6H ) and ii) curved and undulating in the margins (60–80 µm long, Fig. 6I ). Tube feet with supporting rods and plates; end plate absent.

Remarks. Thyonella gemmata was briefly described and not illustrated by Pourtalès (1851). Subsequent authors ( Deichmann, 1930; Deichmann, 1954; Hendler et al., 1995) have provided additional morphological data about this species. In this regard, the specimen herein identified as T. gemmata concurs with these authors’ descriptions, with some differences observed.

According to Hendler et al. (1995), T. gemmata has heavily knobbed buttons. However, Deichmann (1930) pointed out that T. gemmata has buttons with low knobs and this was found in the specimen from Bahamas ( Fig. 6 D–E). The knobbed buttons shown in Hendler et al. (1995) resemble the heavily knobbed buttons of T. sabanillaensis ( Fig. 4A ). The other inconsistency observed was related to the depth of the cups. Some authors ( Deichmann 1930, 1954 and Miller & Pawson, 1984), pointed out that these ossicles are shallow. However, SEM analysis showed that the cups are actually deep (fig. 6A–C).

Figures

FIGURE 4. Thyonella sabanillaensis (Deichmann, 1930) (EH-IBZ/UFRJ 144). SEM images of the ossicles: (A) four-holed button from body wall; (B) smooth plate from body wall; (C–D) knobbed plate from body wall; cup in dorsal (E) and ventral (F) view; (G) button from introvert, (H–I) rods from tentacles and (J) rods from tube feet; (K) triangular plate from body papillae; (L) anal plate. Scale bars: A, 50 µm; B, 100 µm; C, 40 µm; D, 100 µm; E–G, 20 µm; H–L, 100 µm

FIGURE 5. Thyonella gemmata (Pourtalès, 1851) (CASIZ 104737). (A) Specimen preserved in ethanol) and (B) calcareous ring. R, radial plate; IR, interradial plate. Scale bars: A, 10 mm; B, 5mm.

FIGURE 6. Thyonella gemmata (Pourtalès, 1851) (CASIZ 104737). SEM images of the ossicles: (A–C) cups from body wall in lateral and ventral views, respectively, (D–E) four-holed button from body wall in ventral and lateral view respectively, (F) perforated plate from introvert, (G) rosette from introvert, (H–I) rods from tentacles. Scale bars: A–C, 20 µm, D–F, 50 µm, G, 20 µm, H, 100 µm, I, 40 µm.