Psolus tessellatus Koehler, 1896

Massin, Claude, 2013, Redescription of Psolus tessellatus Koehler, 1896 (Echinodermata, Holothuroidea) with neotype designation, European Journal of Taxonomy 38, pp. 1-5 : 2-4

Psolus tessellatus Koehler, 1896

Figs 1 A-D, 2A-G

Psolus tessellatus Koehler, 1896: 119 .

Psolus tessellatus – Mortensen 1927: 414. — Fiege & Janssen 1998: 341, figs 2-3.

Psolus tesselatus – Costelloe et al. 2001: 348.

Redescription

Small oval specimen, 17.4 mm long, 10.6 mm broad and 2.4 mm thick ( Fig. 1A ). Dorsal body wall covered by large scales (from 850 x 550 to 1350 x 1100 µm) ( Figs 1 A-C, 2A). The scale consists of one layer at the edge but rapidly becomes multilayered when going to the centre ( Fig. 2B ). No tube feet dorsally. Ten scales between mouth and anus. Anus surrounded by irregular small plates ( Fig. 1C ). Mouth surrounded by 10 scales: five large triangular scales alternating with 5 small, elongated scales ( Fig. 1A, B ). Tentacles fully retracted, not observed.

Ventral sole very thin, translucent, calcareous ring and digestive tract visible by transparency ( Fig. 1D ). Ossicles as perforated plates, 100-160 µm long with 1-8 holes ( Fig. 2C ). Ventral sole with 2 rows of tube feet at the edge ( Fig. 1D ). Inner row of tube feet large, with perforated rods, 125-280 µm long ( Fig. 2D ) and large end plate in one piece (more or less 300 µm across) ( Fig. 2F ). External row with very small tube feet with small end plates made of one piece (more or less 100 µm across) ( Fig. 2E ). At the base of the large tube feet, perforated plates, 100-170 µm long, similar to those of the ventral sole, sometimes knobbed ( Fig. 2G ). No mid ventral tube feet except 1-2 at the rear ( Fig. 1D ).

Figures

Fig. 1. Psolus tessellatus Koehler, 1896. A. Dorsal view. B. Buccal cone. C. Anal cone. D. Ventral view.

Fig. 2. Psolus tessellatus Koehler, 1896. A. Dorsal scale. B. Detail of dorsal scale. C. Plates of ventral sole. D. Rods of large tube feet. E. End plate of large tube feet. F. End plate of small tube feet. G. Perforated plates at the base of the large tube feet.