Pozziella clavisepta Topsent 1896
Creators: name: Díaz-Agras, Guillermo
Publisher: name: Zenodo
Year: 2008
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Demospongiae
Poecilosclerida
Hamacanthidae
Pozziella
Pozziella clavisepta

description: Pozziella clavisepta Topsent, 1896
(Figs. 1–3, 19)
Examined Material: Pozziella clavisepta (Syntype) MNHN no. 12 P. A 1895 (one preparation of clean spicules).
Description
Habitus: Incrusting sponge, thin, forming more or less extensive patches. Tissue easily separable from substrate, soft. White or greyish ectosome. No visible orifices when viewed without magnification. Choanosome brownish­grey, cavernous and fibrous (Topsent, 1896).
Spicules
Megascleres: Smooth styles, fusiform, shaft straight or slightly curved (Fig. 1 A, B; 2 A–D), in two different size classes. Large styles (style I, Fig. 1 A) 460–550 µm in length (Mean (M.) ± Standard deviation (S.D.), 502.8 ± 24.41 µm) and 12.5–15 µm in width (M. ± S. D., 14.4 ± 1.09 µm) at mid­shaft, latter dimension decreasing towards rounded end to 5–7.5 µm (M. ± S. D., 6.2 ± 1.27 µm) (Fig. 2 A–C) (form index: 0.028). Smaller styles (style II, Fig. 1 B) 280–360 µm in length (M. ± S. D., 316.4 ± 17.77 µm) and 10–12.5 µm in width at mid­shaft (M. ± S. D., 11.5 ± 1.25 µm), latter dimension gradually decreasing to 2.5–5 µm at rounded end (M. ± S. D., 4.9 ± 0.50 µm) (Fig. 2 D) (form index: 0.036).
Exotyles straight or slightly curved, 210–250 µm in length (M. ± S. D., 228 ± 10 µm) and 9–12 µm in width (M. ± S. D., 10.36 ± 0.86 µm), smooth shafts with uniform diameter (Fig. 1 C; 2 E–G). Spherical tyle with width of 15–20 µm (M. ± S. D., 17.41 ± 1.49 µm), covered with small warts (Fig. 2 E, F) (form index 0.045).
Microscleres: Large cyrtancistras of uniform size (Fig. 1 D; 2 H), 310–400 µm in height (M. ± S. D., 355.2 ± 26.94 µm) and 7.5–12.5 µm in width (M. ± S. D., 10.6 ± 1.49 µm). Singular, distinctive, terminal hooks (Fig. 2 I) with smooth body (index form: 0.37). Numerous sigmas with variable curvature and in two size classes (Fig. 1 E, F; 2 J, K). Larger sigmas (type I) horizontally stretched C­shape, actines tending to be parallel, 190–320 µm in height (M. ± S. D., 232 ± 29 µm) and 1 µm in width (M. ± S. D., 1.0 ± 0.0 µm) (index form: 0.94). Smaller sigmas (type II) vertically stretched C­shape, 23–33 µm in height (M. ± S. D., 29.4 ± 2.61 µm﹚ and 1 µm in width (M. ± S. D., 1.0 ± 0.0 µm) (index form: 0.43).
Skeleton
Skeletal arrangement: Styles arranged in long plurispicular fibres in choanosome, interweaved in no particular order in the ectosome. Exotyles inserted vertically in ectosome with tyle pointing outwards and making up the characteristic armour of the genus. Cyrtancistras hooked in fascicles along the choanosomic fibres of styles (Topsent, 1896).
Distribution: Only known from type locality. Azores archipelago, between San Miguel and Terceira. Between 550 and 1165 m depth (Topsent, 1896) (Fig. 19).
Remarks. P. c l a v i s e p t a Topsent, 1896 is the type species of Pozziella and is clearly distinguishable from the other species by the presence of two different kinds of sigmas.
The existence of two types of styles is not mentioned in the original description of P. c l a v i s e p t a Topsent, 1896. Topsent (1904) does, however, mention it superficially. Our examination of the syntype confirmed the presence of two types of styles of different length (Fig. 3).
description: Published as part of Díaz-Agras, Guillermo, 2008, Revision of the genus Pozziella (Porifera: Poecilosclerida) with description of three new species from the eastern Pacific *, pp. 69-94 in Zootaxa 1866 on pages 70-73, DOI: 10.5281/zenodo.183749