Pozziella aperta Topsent 1920
Creators: name: Díaz-Agras, Guillermo
Publisher: name: Zenodo
Year: 2008
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Demospongiae
Poecilosclerida
Hamacanthidae
Pozziella
Pozziella aperta

description: Pozziella aperta (Topsent, 1920)
(Figs. 3–5, 19)
Examined material: Hamacantha clavisepta var. aperta (Syntype) MNHN LBIM no. D.T 2155 (one preparation of clean spicules).
Description
Habitus: White and opaque crust. Beginnings of some choanosomic lines hanging from the inner surface of the ectosome. Exotyles standing out on the surface of the sponge, resulting in slightly hispid aspect (Topsent, 1920).
Spicules
Megascleres: Small styles (II), smooth, small, fusiform and slightly curved (Fig. 4 A; 5 A–C), 250–470 µm in length (M. ± S.D., 373 ± 70.29 µm) and 10–17.5 µm in width at mid­shaft (M. ± S.D., 14.40 ± 2.08 µm), latter dimension decreasing towards rounded end to 5–7.5 µm (M. ± S.D., 6 ± 1.25 µm) (form index: 0.04).
Smooth exotyles, straight or slightly curved (Fig. 4 B; 5 D). Tyle in the shape of a spherical mace, covered by shapeless creases, opposite end rounded. Diameter of the spicule increasing towards the rounded end (Fig. 5 E, F), 165–197.5 µm in length (M. ± S.D., 186.30 ± 8.169 µm), 10–12.5 µm shaft width in mid­region (M. ± S.D., 11.4 ± 1.27 µm), tyle width of 10–20 µm (M. ± S.D., 16.40 ± 2.61 µm) (form index 0.088).
Microscleres: Smooth cyrtancistras of two different types. Larger cyrtancistras (type I) vertically stretched C­shape, 360–460 µm in height (M. ± S.D., 423.57 ± 31.77 µm) and 12.5–20 µm in width (M. ± S.D., 16.07 ± 2.72 µm) (form index: 0.35) (Fig. 4 C; 5 G, H). Smaller cyrtancistras (type II) C­shaped, with strong angulation in middle and almost parallel arms, 102.5–157.5 µm in height (M. ± S.D., 131.25 ± 17.17 µm) and 3–5 µm in width (M. ± S.D., 4.29 ± 0.61 µm) (form index: 0.540) (Fig. 4 D; 5 I). Abundant small and strong type II sigmas (Fig. 4 E; 5 J), 18–26 µm in height (M. ± S.D., 21.68 ± 2.23 µm) and 1 µm in width (M. ± S. D., 1.0 ± 0.0 µm) (form index: 0.39).
Distribution: Only known from type locality. Caribbean Sea (Topsent, 1920) (Fig. 19).
Remarks: Hajdu (2002) considered Topsent’s (1920) variety Hamacantha clavisepta var. aperta a valid species on its own: ‘ Topsent (1920) described Hamacantha clavisepta var. aperta from the West Indies. This is clearly a Pozziella, and is considered here a valid species, Pozziella aperta, on account of diagnostic morphological features and likely biogeographical isolation. It differs from the type species by the possession of a second category of much smaller cyrtancistras (larger ones up to 473 µm, smaller ones up to 167 µm)’. Hajdu’s (2002) decision is here supported, as P. aperta has cyrtancistras typical of Pozziella, but not of Hamacantha, choanosomic plurispicular fascicula and a rather uniform layer of exotyles that make up the ectosome, what is also characteristic of the genus Pozziella.
P. aperta differs clearly from the other species of the genus because it is the only one that has two types of cyrtancistras, clearly distinguishable by their size and form, with the smaller type having an angle in midregion. The exotyles of P. aperta have a tyle in the shape of a spherical mace similar to that of P. clavisepta and P. neuhausi sp. nov. However, in P. neuhausi sp. nov. the tyle is covered by a thin layer of granulae, whereas in P. clavisepta it shows irregular creases as those of P. aperta. In addition, P. aperta differs from the other two species by having longer and thinner exotyles with a form index of 0.088, whereas in the other two species the indices are 0.045 and 0.027 respectively. Moreover, the shaft of the exotyle of P. aperta is maceshaped and its diameter wider in the mid and lower region than in the upper half, a characteristic which is not shared by the other species of the genus.
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 73-77, DOI: 10.5281/zenodo.183749