Tethya ignis sp. nov.

(Fig. 2 C, 5)

Holotype. MNRJ 5322a, Redonda Island, Abrolhos Archipelago, Bahia State, Brazil, 03/ iii/2002, coll. S. Ribeiro, intertidal.

Diagnosis. Tethya orange, with tylasters and completely microspined oxyasters.

Description. Body hemispherical, 1.5 cm in diameter by 1.0 cm high (Fig. 2 C, 5A). Colour in life orange; cortex white or yellow and choanosome yellowish brown in alcohol. Surface smooth or with flattened tubercles separated by up to 1 mm. The surface between adjacent tubercles is reticulated. Buds attached to sponge surface. Oscules not visible. Cortex firm, choanosome soft.

Cortical skeleton (Fig. 5 B). Cortical layer 1000–2000 m thick. Spherasters scattered in the cortex. Tylasters especially abundant in the surface, forming a dermal crust. Occasionally, some megascleres project beyond the surface. Regular cavities, 300–800 m in diameter, located between megascleres bundles.

Choanosomal skeleton (Fig. 5 B). Tylasters abundant in the upper choanosome. Spherasters rare, located near the cortical region.

Spicules. Main strongyloxeas 604–816– 1.063 m long by 10–14– 21 m wide (n=30) (Fig. 5 C). Accessory strongyloxeas 302–432– 566 m by 5–8– 11 m (n=30). Spherasters 29–53– 68 m (n=20), R/C = 0.5–1.0 (Fig. 5 D). Completely microspined oxyasters 25 m in diameter (Fig. 5 E–F). Tylasters (Fig. 5 E) generally with short rays, 10–13– 18 mm (n=10).

Distribution and ecology. Endemic from Abrolhos Archipelago, Bahia state, Brazil, found only in Redonda Island. This species occurs in the intertidal zone and was found on the underside of boulders. Tethya ignis sp. nov. is very rare, and only a single specimen has been found despite extensive search.

Etymology. The name ignis refers to the orange external colour of the new species.

Remarks. Tethya ovum, T. ensis, T. norvegica Bowerbank, 1872 (Sarà et al. 1992), T. ornata Sarà et al., 2000 and T. diploderma sensu de Laubenfels (1953) (non sensu Schmidt) are similar because they all have completely spined asters. They differ however from the new species in other characters: Tethya ensis and T. ovum have microspined tylasters instead of oxyasters; Tethya ornata has completely microspined strongylasters; Tethya norvegica has micrasters with conical rays (similar to spherasters, 10 m in diameter), absent in the new species. Tethya diploderma sensu de Laubenfels 1953 has oxyasters with smooth or microspined, bifurcated rays, which are absent in Tethya ignis sp. nov.