Thorecta cincta Boury-Esnault 1973, new combination

Thorecta cincta (Boury-Esnault, 1973), new combination

(Figs. 2–3)

Cacospongia cincta Boury-Esnault, 1973: 290; Hechtel, 1976: 252; Santos et al., 2002: 397. Scalarispongia cincta, Muricy et al., 2011: 63.

Material examined. Holotype MNHN. LBIM.D.NBE 1017 (fragment deposited in UFRJPOR 3434), Off Recife city (8º19’S – 34º39’W), Pernambuco State, Brazil, 75 m depth, Calypso sta. 23, 21 Nov 1961 (Fig. 1).

Diagnosis. Thorecta pear-shaped, with conulose surface, one large apical oscule and many small oscula forming a sub-equatorial belt.

External Morphology (Fig. 2 A–D). Habit massive, pear-shaped to ficiform, 10.5 cm high by 7.5 cm maximum width. Color is purplish-brown in vivo, becoming dark brown in ethanol. The surface is irregularly conulose, with blunt, folded conules up to 2 mm in height and 2–4 mm apart. The tips of the conules are finely rugose due to the extremities of fiber clusters that protrude slightly beyond the surface. Grooves are present between some of the conules. The surface is thick, detachable, coriaceous. There is one large oscule at the top of the sponge and a sub-equatorial belt of smaller oscula. The consistency is firm and slightly compressible.

Skeleton (Fig. 3 A–E). Dermal armour regular, granular, 340 µm thick (Fig. 3 A). Choanosome cavernous. A regular ladder-like network of concentrically laminated primary and secondary fibers forms the choanosomal skeleton (Fig. 3 C). Near the surface the fibers are thinner and the reticulation is less dense, with rounded meshes (Fig. 3 B). Primary fibers are axially cored by small amounts of debris, and may form fascicles (Fig. 3 D). These fibers are uncored in the internal part of skeleton, where a granular pith can be observed. The secondary fibers are uncored and connect the primary fibers in right angles (Fig. 3 E). Primary fibers 50–77–110 µm in diameter (n = 10) and secondary fibers 30–47–70 µm in diameter (n = 10). The meshes are mostly rectangular, but a few are circular or ovoid: 50–224–470 by 50–164–320 µm.

Bathymetry. The specimen was collected at 75 m depth.

Geographical distribution. Endemic from Brazil: Off Recife, Pernambuco State.

Remarks. This specimen was originally allocated in the genus Cacospongia, based on the presence of cored primary fibers and uncored secondary fibers (Boury-Esnault, 1973). Later, it was transferred to Scalarispongia based on Cook & Bergquist (2000) due its regular fiber skeleton (Muricy et al., 2011; van Soest et al., 2016). In this study, we show that this sponge has in fact an armoured dermal layer of foreign debris not mentioned in the original description, which, together with the cored primary fibers, uncored secondary fibers and rectangular meshes makes it fit better in the genus Thorecta sensu Cook & Bergquist (2002).

The genus Thorecta is distributed mostly in the Indo-Pacific. To date, only Thorecta atlantica was recorded from the Tropical Western Atlantic Ocean (Santos et al., 2010), and it has distinctive characteristics when compared with Thorecta cincta n. comb.: the former has surface smooth or rugose, with closely-spaced irregular openings, large oscule with a large atrium, hard consistency, thicker fibers (up to 300 µm in width) and larger meshes (up to 2400 µm in diameter), whereas the latter is fig- or pear-shaped, has a conulose surface with rugose conules, a single apical oscule without atrium, a sub-equatorial belt of smaller oscules, thinner fibers (up to 110 µm) and smaller meshes (up to 470 µm).