Description

Description: Fragile, encrusting sponge growing on Solenosmilia variabilis approximately 30 mm x 10 mm x 2 mm in height (Fig. 5 A, B). The sponge had a smooth surface without any visible oscules. The sponge was white on deck and opaque white in ethanol preservative. Skeleton: The ectosomal skeleton is a tangential array of styles (Fig. 5 C, D). On the lower layer of the ectosomal skeleton are numerous diancistras of both sizes. The choanosomal skeleton consists of ascending bundles of styles that diverge to provide support to the ectosomal skeleton (Fig. 5 C). Spicules: The megascleres are styles, which are abundant, fusiform, straight, sharply pointed, and thickest in the centre (Fig. 5 H). The blunt end is much narrower than the middle and has a rounded terminal tyle occasionally with a slight subtylostylote swelling. They measure 292 – (385) – 437 x 7.6 – (9.9) – 12.6 μm, n = 35. The large diancistras (I) are common, with the shaft twisted at least 45 o, the thin sharp fimbriae run the entire length of the inner surface except around the notch (Fig. 5 E). They measure 83 – (96) – 105 x 5.0 – (8.8) – 12.5 μm, n = 42. The smaller diancistras (II) are also common, with the shaft twisted 90 o, have large, equal, almost touching curvaceous fimbriae (Fig. 5 G). They measure 19 – (24) – 30 x 1.0 – (1.1) – 1.7 μm, n = 29. Microscleres are small rare oxbow toxas that measure 48 – (54) – 65 x 2 – (2) – 2 μm, n = 13 (Fig. 5 G).

Common Names

Taxonomic Hierarchy

Kingdom: Animalia

Phylum: Porifera

Class: Demospongiae

Order: Merliida

Family: Hamacanthidae

Genus: Hamacantha

Species: Hamacantha ridleyi Ekins, Baker & Hooper, 2023