Tethya cyanae, Ribeiro, Suzi M. & Muricy, Guilherme, 2004

Ribeiro, Suzi M. & Muricy, Guilherme, 2004, Four new sympatric species of Tethya (Demospongiae: Hadromerida) from Abrolhos Archipelago (Bahia State, Brazil), Zootaxa 557, pp. 1-16 : 7-9

Tethya cyanae sp. nov.

( Fig. 4 )

Holotype. MNRJ 6723, Siriba Island, Abrolhos Archipelago, Bahia State, Brazil, 25/x/ 2002, coll. E. Esteves, 1 m depth.

Diagnosis. Tethya dark blue externally, with tylasters, oxyasters and microoxyasters.

Description. Body hemispherical, 1.4 cm in diameter by 1.2 cm high ( Fig. 4 A). External colour in life dark blue, with yellow interior; it becomes gray in alcohol. Surface tuberculate. Buds attached to sponge surface, up to 0.5 mm in diameter. Oscules are not visible in the preserved material. Cortex firm, choanosome fragile and compressible.

Cortical skeleton ( Fig. 4 B). Cortical layer 900–1500 m thick. Megasclere bundles with terminal fans, 250–1000 m in diameter. Irregular cavities, 175–300 m in diameter, occur in the middle cortex. A collagenous layer form the boundary between the cortex and the choanosome. Spherasters abundantly distributed, mostly near cavities and megasclere bundles. Tylasters abundant in all cortical region.

Choanosomal skeleton ( Fig. 4 B). Exogenous particles commonly distributed in the choanosome. Oxyasters abundant throughout the choanosome. Regular cavities absent. Megasclere bundles 100–175 mm thick. Spherasters rare, more concentrated in the upper choanosome, near the boundary between cortex and choanosome.

Spicules. Main strongyloxeas ( Fig. 4 C) 760–1026– 1384 m long by 10–13– 16 m (n=30). Accessory strongyloxeas 380–532– 692 m x 5–7 – 8 m (n=30). Spherasters ( Fig. 4 D, E) 21–31– 42 m in diameter (n=20), R/C 0.5–0.7–1.0. Oxyasters with long and irregularly spined rays ( Fig. 4 F), 22–26– 31 m (n=10). Microoxyasters with thin, long rays, without apparent nucleus, 7–7.5– 8 m (n=10) ( Fig. 4 H). Tylasters ( Fig. 4 F–H) with robust and almost isodiametric rays, distal end spined and expanded, 6–8– 9 m (n=10).

Distribution and ecology. Endemic from Abrolhos Archipelago, Brazil, found so far only in Siriba Island. Tethya cyanae sp. nov. occurs in the intertidal zone, on the undersurfaces of boulders, and it is a very rare species. Filamentous algae was found associated to the skeleton, similarly to Tethya seychellensis from the Caribbean ( Gaino & Sarà 1994).

Etymology. The name cyanae refers to the blue colour of this species.

Remarks. Seven species share with T. cyanae sp. nov. the presence of oxyasters in the choanosome: T. simi Sarà et al., 2000 , T. magna Kirkpatrick, 1904 , T. viridis Baer, 1905 , T. seychellensis sensu Bergquist & Kelly­Borges (1991) , T. actinia de Laubenfels, 1950, T. ingalli Bowerbank, 1872 , and T. multifida ( Carter, 1882) . However, only T. seychellensis sensu Bergquist & Kelly­Borges (1991) also has microoxyasters as the new species. The specimens described by Bergquist & Kelly­Borges (from New Guinea, Australia and Jamaica) are yellow, and its megasclere bundles are branched and project beyond the surface. None of these features were observed in the new species which, in addition, is the only known species of Tethya with blue colour.

Figures

FIGURE 4. Tethya cyanae sp. nov. A, preserved holotype (MNRJ 6723); B, architecture of the ectosome and choanosome; C, strongyloxea; D, spheraster; E, spheraster and tylaster; F, oxyaster and tylaster; G, tylaster; H, microoxyaster and tylasters. B – C, LM; D – H, SEM.