Oceanapia fistulosa ( Bowerbank, 1873 )

Calcinai, Barbara, Bavestrello, Giorgio, Bertolino, Marco, Pica, Daniela, Wagner, Daniel & Cerrano, Carlo, 2013, Sponges associated with octocorals in the Indo-Pacific, with the description of four new species, Zootaxa 3617 (1), pp. 1-61 : 54

Oceanapia fistulosa ( Bowerbank, 1873)

( Fig. 35 A–H)

Examined material. Sample Bugor 514: Indonesia, North Sulawesi, Bunaken Island, Pangalisang, 25 m, 11 September 2007.

Description. Massive sponge, with ovoid or spherical body; the sponge lives completely buried in the sediment, with only fistular chimneys above the substrate surface. Inhalant closed fistules with short, apical digitations; only fistules were collected; they are up to 17 cm high, with a diameter about 0.5–2 cm ( Fig. 35 A–C). In the area of the Bunaken National Park the fistules of this sponge were frequently observed covered by the octocoral Alertigorgia hoeksemai ( Fig. 35 A, C), which was obscuring the sponge below. The colour of the fistules is vivid pink ( Fig. 35 A), pale yellowish in ethanol ( Fig. 35 B).

Skeleton. Only the fistular skeleton was examined. The ectosome is a tangential reticulum of oxeas; the surface is microhispid due to groups of oxeas piercing it at the nodes ( Fig. 35 D). The ectosomal skeleton is supported by ascending tracts opening in irregular fans ( Fig. 35 E). The internal surface of the hollow fistules is supported by longitudinal, thick parallel tracts of oxeas ( Fig. 35 E). In the fistular areas covered by the octocoral, the sponge skeleton appears modified as the ascending tracts, opening in fans and supporting the tangential ectosomal skeleton, are not present ( Fig. 35 F).

Spicules. Oxeas of usual shape, in two size classes: oxeas I ( Fig. 35 G), 210 – (242.6 ± 12.9) – 260 x 10 – (10.9 ± 1.2) – 12.5 µm; oxeas II ( Fig. 35 H), 82.5 – (90.5 ± 5.6) – 102.5 x 3.5 – (4.5 ± 0.6) – 5 μm. Small and thin oxeas, probably growing forms, are also present.

Distribution and remarks. Australia ( Ridley 1884), Indonesia ( Topsent 1897) and Indian Ocean ( Dendy 1922 ). This species is very common in the Bunaken National Park ( Bavestrello et al. 2002; Cerrano et al. 2007).

Figures

FIGURE 35. Oceanapia fistulosa (Bowerbank, 1873). A, Sponge (black arrows) covered by Alertigorgia hoeksemai (white arrow) in situ; B, Magnification of the pinkish surface of the fistule free from the octocoral; C, Section of a sponge fistule (S) covered by the octocoral (O); D, Ectosome composed of a tangential reticulum of oxeas; E, Longitudinal section of a fistule showing longitudinal thick tracts of oxeas (black arrow) and tracts supporting the ectosome (white arrow); F, Section of a fistule of the sponge (S) covered by the octocoral (O); spicule bouquets not present, and the arrow indicates the boundary between the sponge ectosome and the medulla of the octocoral; G, Oxea I; H, Oxea II.