Placospherastra antillensis

Rützler, Klaus, Piantoni, Carla, Van, Rob W. M. & Díaz, Cristina, 2014, Diversity of sponges (Porifera) from cryptic habitats on the Belize barrier reef near Carrie Bow Cay, Zootaxa 3805 (1), pp. 1-129 : 33-34

Placospherastra antillensis van Soest, 2009

( Figure 17 )

Synonymy and references. Placospherastra antillensis van Soest, 2009: 6, figs. 2A–E, 3A, B.

Material. USNM 1228942, Curlew Bank forereef cave, 20 m. C. Piantoni col. 29 Jun 2007. USNM 1228943, 1228944, Curlew Bank forereef cave, 20 m; C. Piantoni col. 2 July 2007.

External morphology. An encrustation covering about 35 cm 2, 2– 5 mm thick. Cortical plates at the surface are indicated by polygonal ridges that open as pore grooves when the sponge is alive and active. Consistency is hard, the surface rough, color in life is bright orange at the surface, brownish orange inside.

Skeleton structure. A cortex is made up by a dense layer of spherasters cemented into polygonal plates. Tracts of tylostyles run from the sponge base toward the cortex, points outward. Various astrose microscleres form a layer below the cortex and are dispersed throughout the tissue.

Spicules. Straight tylostyles, most with spherical tyles of about the same width as the center of the shaft, with pointed end rounded; considerable size range without clear separation into classes: 218–720 x 7–18 (299 x 12) Μm; spherasters with large center (about 75% of diameter), with broad-based rays that, in young stages, have a crenulated surface, in mature spicules are microspined near their points: 15–50 (32) Μm; diplasters, with long, slim rays emerging in clusters from two or three positions on the short shaft: 13–20 (17) Μm; micro-amphiasters and –spirasters, possibly developmental stages of the diplasters: 3–5 (4) µm.

Ecology. Under reef rubble and in caves, 20– 25 m.

Distribution. First described from the Southeastern Caribbean, this record from Belize indicates a Caribbeanwide Distribution.

Comments. Some spicule dimensions are larger than those given in the original description (van Soest, 2009) but most morphological details agree well. One curious exception is the microspination surrounding the conical rays of the spherasters (shown in van Soest’s fig. 2C, D), which is always at the tip of the rays in our specimen ( Figure 17 b).

Figures

FIGURE 17. Placospherastra antillensis, spicules (SEM): a, tylostyles; b, spherasters; c, spirasters / diplasters.