Tethya rubra sp. nov.

(Fig. 2 D, 6, Table 2)

Holotype. MNRJ 5316, Siriba Island, Abrolhos Archipelago, Bahia State, Brazil, 04/iii/ 2002, coll. S. Ribeiro, intertidal.

Paratypes. UFRJPOR 4735 (Redonda Island, 30/x/1997, coll. G. Muricy), MNRJ 5320 (Siriba Island, 04/iii/2002, coll. E. Esteves), MNRJ 5321 (Siriba Island, 04/iii/2002, coll. S. Ribeiro), all from the intertidal zone in Abrolhos Archipelago.

Diagnosis. Tethya red or yellow externally, and always yellow internally. Micrasters are tylasters and oxyasters larger than 20 m, with branched and twisted rays.

Description. Sponge spherical or flattened, 2.0– 2.3 cm in diameter by 1.0– 2.3 cm high (Fig. 2 D, 6A). Colour in life red or yellow (always yellow internally); cortex white or yellow and choanosome yellowish brown in alcohol. Surface smooth or tuberculate, tubercles irregular in size and shape. In some regions a thin reticulation is visible in the surface between tubercles. Buds, up to 2 mm in diameter, attached to sponge surface or supported by stalks. Oscules not visible. Cortex firm, choanosome soft.

Cortical skeleton (Fig. 6 B). Cortical layer 500–1500 m thick. Megasclere bundles expanded, fanning out in the surface, 1000–1750 m in diameter. Spicules in the bundles are poorly organized, and sometimes bundles may branch out. Regular, rounded lacunae (250–875 m) occur between the bundles. Spherasters abundant in the whole cortex, but especially in the outer region. Tylasters concentrated in the surface, making a dermal crust.

Choanosomal skeleton. Rounded or elongated cavities, 100–625 m in diameter, scattered in choanosome. Spherasters present in low abundance, becoming rarer towards the center of the sponge. A collagenous layer marks the boundary between cortex and choanosome. Oxyasters and exogenous particles present only in choanosome. Megasclere bundles 150–300 m thick.

Spicules (Table 2). Main strongyloxeas 604–862– 1426 m long by 5–19– 45 m in diameter (Fig. 6 C). Accessory strongyloxeas 291–477–633 x 3 –4.8– 11 m. Spherasters with accerated rays, 18–34.5– 50 m in diameter, R/C = 0.5–1.0 (Fig. 6 D–E). Oxyasters with branched, straight or twisted rays, 21–27.5– 42 m in diameter (Fig. 6 F–G). Tylasters with 4–6 (most often six) cylindric, almost isodiametric rays, 5–9– 13 m in diameter (Fig. 6 G–H).

Distribution and ecology. Abrolhos Archipelago (Bahia state), Recife and Ipojuca (Pernambuco state; authors’ unpublished observations). The species occurs in the underside of boulders in the intertidal zone, and is very rare.

Etymology. The name rubra refers to the external colour of this species, although yellow specimens were also found.

Remarks. Tethya simi, T. magna, T. viridis, T. seychellensis, T. actinia, T. ingalli and T. multifida are similar to the new species due to their choanosomal oxyasters. However, T. simi and T. multifida have cortex without lacunae, thus differing from the new species. Tethya magna differs from T. rubra sp. nov. mainly by the larger size of its strongyloxeas and spherasters. Tethya actinia is very similar to T. rubra sp. nov. in its frequently branched oxyasters, but it has strongyloxeas up to 2000 m long and spherasters with high R/C (= 1.0), being thus differentiated from the new species. Tethya viridis differs from T. rubra sp. nov. by the absence of both the dense collagenous layer and the bifurcated oxyasters. Tethya seychellensis differs from the new species by its oxyasters with straight rays, tylasters with few (3–6), often abnormal rays, and cortical lacunae with sinuous and irregular shape. Tethya rubra sp. nov. is characterized mainly by its oxyasters with sinuous, bifurcated or trifurcated rays, and by the colour in red specimens.