Geodia globostellifera Carter, 1880
Geodia globostellifera; Burton, 1959: 195.
Material.— ZMA Por. 17028, Khuriya Muriya Islands, Al Hallaniyah main island, intertidal, 17.49222 N 55.96667 E, 12-11-1991, coll. R.G. Moolenbeek & H. Dekker, moo91/61, nr. 4.
(N.B.: the BMNH specimen, Oman, 17.483 N 55.783 E, 95 m, John Murray Exped. stat. 43, 28-10-1933, could not be found in a recent search).
Description.— Fragments of a massively encrusting sponge, agglutinating and covering small stones and rubble, with several upright digitations 1-2 cm high, 1 cm diameter (fig. 8h). Surface smooth but rough to the touch. One fragment shows a cribriporal patch, presumably exhalant. Cortical skeleton approximately 1-1.5 mm thick, difficult to cut or tear. Interior pulpy, clearly separated from the cortex.
Colour.— Pale grey in alcohol.
Skeleton.— The cortex consists of a dense crust of sterrasters and small asters mixed with small cortical oxeas, carried by the cladi of a subdermal layer of parallel bundles of orthotriaenes and oxeas. Choanosomal skeleton confused with ill-defined bundles of oxeas and interspersed oxyasters. A single small anatriaene was found, which may be proper.
Spicules.— Orthotriaenes, oxeas, sterrasters, euasters. Orthotriaenes (fig. 10a), with recurved cladi with in some younger stages plagiotriaene or protriaene shapes, but obviously being the same spicule category, 498-1101.3-1520 × 9-40.0-52 µm, cladi 64-189.2-362 × 5-16.0-36 µm. Oxeas (fig. 10b) of the choanosome: thinly fusiform, sharply pointed, 880-1146.0-1407 × 12-15.9-25 µm; of the cortical layer: thin, sharply pointed, 102-172.1-206 × 2-3.2-4 µm. Sterrasters (figs 10c, d) globular, evenly rounded, with many smaller growth stages (fig. 10d), 42-60.6-81 µm, measured using only mature sterrasters with rays secondarily branched. Small, multirayed spheroxyasters (fig. 10f) of the cortical sterraster layer, 4-7.4-12 µm diameter. Larger, multirayed spheroxyasters (fig. 10g) of the choanosome, rare, 15-18 µm diameter. Oxyasters of the choanosome (fig. 10e), usually 8-rayed, with spined rays, 14-20.4-33 µm diameter.
Fig. 10. Geodia globostellifera Carter, 1880, ZMA Por. 17028, A. orthotriaene, B, oxeas, C-D, sterrasters, E, oxyaster, F, tylaster, G, strongylaster.
Ecology.— Encrusting intertidal stones and insinuating crevices. Burton’s Oman record was from 95 m.
Remarks.— There are a few discrepancies between the original material from the Gulf of Manaar, India, and our material, especially the larger size of the structural oxeas (up to 2390 µm in length in the type), but most aspects and spicule sizes and categories are similar, so the identification is made with confidence. Other records of this species are from North Australia (Ridley, 1884 and Bergquist & Tizard, 1987) and likewise these record larger oxeas than in our material (up to 3000 µm in Ridley’s material). Bergquist & Tizard (l.c.) call the triaenes in their material plagiotriaenes, but it is here assumed that they were similar in shape to Carter’s and Ridley’s triaenes, which are clearly orthotriaenes in the adult spicules. Some of the younger triaenes have their cladi more or less straight (plagiotriaene-like) or even in-curved (protriaene-like). All records so far agree that this species is encrusting and has a spiculation of orthotriaenes, oxeas, cortical oxeas, small globular sterrasters and three further euaster categories: small cortical spheroxyasters, larger choanosomal spheroxyasters, and large choanosomal oxyasters. It is widespread in the tropical Indian Ocean and adjacent Western Pacific.
Geodia punctata Hentschel, 1909 from Western Australia is closely similar in most features, but no mention is made of cortical oxeas, and almost all spicule categories are smaller than in our specimens. If cortical oxeas have been overlooked by Hentschel, his material fits better with ours, than Carter’s or Bergquist’s material. G. punctata would in that case be a likely junior synonym of a rather more variable G. globostellifera. This species appears one from a complex of closely similar encrusting Geodia species, characterized by the possession of relatively short orthotriaenes, relatively small sterrasters, and tiny ectosomal spherasters, to which a.o. can be counted G. paupera Bowerbank, 1873 (no original locality known), G. exigua Thiele, 1898 (Japan),