Stelletta anasteria, Esteves & Muricy, 2005

Esteves, Eduardo L. & Muricy, Guilherme, 2005, A new species of Stelletta (Demospongiae, Astrophorida) without microscleres from Abrolhos Archipelago, northeastern Brazil, Zootaxa 1006 (1), pp. 43-52 : 45-48

Stelletta anasteria sp. nov.

( Figs. 2 , 3 , Table 1)

Holotype. Brazil, Bahia state, Abrolhos archipelago: MNRJ 6710 , north coast of Santa Barbara Island , 2 m depth, under a boulder, E. L. Esteves coll., 24/X/2002.

Paratypes. Brazil, Bahia state, Abrolhos archipelago: MNRJ 6699 , north coast of Santa Barbara Island , 1 m depth, under a boulder, E. L. Esteves coll., 24/X/2002 ; MNRJ 6713 , north coast of Santa Barbara Island , 2 m depth, under a boulder, E. L. Esteves coll., 24/X/2002 .

Diagnosis. Stelletta without microscleres, and with plagiotriaenes, anatriaenes and oxeas less than 590 m long. Clads of plagiotriaenes smaller than 70 m long and those of anatriaenes smaller than 20 m long. Anatriaenes with ill­formed and/or additional clads along the rhabdome are common.

Description ( Fig. 2A ). Thickly encrusting to sub­spherical sponge, 1.1 x 1.3 cm wide and 0.5 cm high to 1.4 x 1.9 cm wide and 0.8 cm high. Color pale beige in life and after fixation, both externally and internally. Oscules not evident. Sediment, mollusc valves and sea urchin spines are embedded in the surface of the body. Surface even, smooth or rough due to the presence of incorporated sediment debris. Consistency rather firm, slightly compressible.

Internal anatomy. Ectosome with a distinct collagenous cortex (78–136 m thick). Oxeas rarely pierce the ectosome ( Fig. 2B ). Small subdermal cavities (63–160 m in diameter) are abundant just below the cortex. Choanosomal skeleton formed by oxeas and anatriaenes disorganized at the inner part of the body, with ascending tracts of oxeas, anatriaenes and plagiotriaenes near the cortex ( Fig. 2B–C ). Spherulous cells dispersed in great abundance throughout the choanosome, but absent in the cortex ( Fig. 2D ).

Spicules ( Fig. 3 , Table 1). Plagiotriaenes with straigth rhabdome, thickest underneath the cladome, sharply pointed: 210­360­491/2­6­ 9 m; cladome 23­58­ 95 m wide, with robust conical clads ( Fig. 3A ): 10­34­63/2­5­ 8 m. Anatriaenes with the rhabdome straigth or slightly curved, conical or with a regular thickness along the shaft, sharply or abruptly pointed: 202­401­509/2­4­ 5 m; cladome 11­19­ 25 m wide, with short clads ( Fig. 3B ): 5­11­ 16 m long. Anatriaenes with ill­formed and/or additional clads between the middle part of the rhabdome and the cladome are common. Oxeas fusiform, straigth or slightly curved, tappering gradually to sharp points ( Fig. 3C ): 242­449­559/2­5­ 8 m. Microscleres absent.

Ecology. Stelleta anasteria sp. nov. is rare in Abrolhos archipelago. The three specimens were found under large boulders at the north coast of Santa Barbara Island from 1 to 2 m depth. One specimen was encrusted by an ascidian ( Fig. 2A ).

Distribution. Provisionally endemic from Abrolhos archipelago, Bahia state, Brazil.

Etymology. The name anasteria refers to the absence of asters.

Figures

FIGURE 2. Stelletta anasteria sp. nov. A, preserved specimen (holotype MNRJ 6170; an ascidian is attached to the surface in the upper right portion of the specimen); B, cortex and periphery of the choanosome in cross section; C, choanosome in cross section; D, spherulous cells near the cortex (co — cortex; sc — subdermal cavity).

FIGURE 3. Stelletta anasteria sp. nov. Spicules: A, plagiotriaenes; B, anatriaenes; C, oxeas.