Ascoleuceta gabensis, Klautau & Lopes & Tavares & Rizzieri & Sorokin & Fromont & Goudie & Crowther & McCormack & George & Wahab, 2025

AscoleuceTa gabensis sp. nov.

( Figs 9, 10; Table 5)

Zoobank registration: urn:lsid:zoobank.org:act:

Etymology: From the type locality, the GAB.

Diagnosis: Ascoleuceta with a globular body and single osculum. Cortex with large triactines and small triactines. Choanocyte tubes with few huge triactines and many small triactines and tetractines. Atrialskeletoncomposedofsmalltriactinesandfewlargetriactines.

Type material: Holotype, SAMA S1917, GAB, 33°20 ʹ 13″S, 130°15 ʹ 27″E, depth: 189 m, coll. GABRP, site IN2015 _ C02_395, 15 December 2015 GoogleMaps . Paratype, SAMA S1875, GAB, 34°16 ʹ 33″S, 132°41 ʹ 29″E, depth: 209 m, coll. GABRP, site IN2015 _C02_179, 7 December 2015 GoogleMaps .

Additional material examined: SAMA S1880, GAB, 34°16 ʹ 33″S, 132°41 ʹ 29″E, depth: 209 m, coll. GABRP, site IN2015 _ C02_179, 7 December 2015 GoogleMaps . SAMA S1934, GAB, 33°22 ʹ 00″S, 130°44 ʹ 08″E, depth: 198 m, coll. GABRP, site IN2015 _ C02_398, 15 December 2015 GoogleMaps .

Colour: Beige in ethanol ( Fig. 9A).

Morphology and anatomy: Sponge globular to subglobular, with single and simple apical osculum. Te cortex is formed by irregular and tightly anastomosed tubes ( Fig. 9A–C). In the choanosome, tubes are larger and run almost parallel to each other, hence the anastomosis is not evident ( Fig. 9B). Te atrium resembles a tube. Aquiferous system solenoid.

Te inhalant canals do not have any ornamentation or have few trichoxeas (e.g. SAMA S1880; Fig. 9C). Te cortical skeleton is composed of large and small triactines ( Fig. 9C), and the choanosome has large and small triactines and also tetractines. Te atrial skeleton is composed mostly of small triactines, but large triactines are also present ( Fig. 9D). Te small triactines are, in fact, two different types of spicules, conical or cylindrical. Tetractines are always cylindrical.

Spicules ( Table 5)

Large triactines: Regular (equiangular and equiradiate) or sagital. Actines are conical, with blunt tips ( Fig. 10A). Frequently, they have at least one actine undulated or bent in the specimen SAMA S1875. Size: 486.0 (±101.2)/52.8 (±10.7) µm.

Small conical triactines: Regular (equiangular and equiradiate). Actines are conical, with blunt to rounded tips ( Fig. 10B). Size: 189.4 (±36.4)/18.1 (±3.5) µm.

Small cylindrical triactines: Regular (equiangular and equiradiate) or sagital. Actines are cylindrical, with blunt to rounded tips ( Fig. 10C). Size: 135.0 (±20.1)/9.1 (±1.1) µm.

Small tetractines: Regular (equiangular and equiradiate) or sagital. Actines are cylindrical, with blunt to rounded tips ( Fig. 10D). Te apical actine is very thin (needle-like), sharp, smooth, and, frequently, undulated ( Fig. 10E). Size: basal, 135.8 (±15.4)/9.1 (±1.0) µm; apical, 96.5 (±22.5)/4.5 (±0.6) µm.

Geographical distribution: Currently known from three localities in the GAB.

Ecology: Tis species was found in depths ranging from 189 to 209 m on the edge of the continental shelf (in fine sand and silt).

Taxonomic remarks: Tere are currently only two species of Ascoleuceta : Ascoleuceta compressa , the type species of the genus, originally described from Abrolhos Island ( Australia) and Ascoleuceta oentricosa ( Carter, 1886) , a species from Port Phillip Heads ( Australia). Ascoleuceta gabensis can be differentiated from both mainly by the shape of the actines of the small triactines and tetractines, which are conical in the known species and cylindrical in the new one, and by the absence of tetractines in the atrial skeleton. In addition, the larger triactines have much longer actines in the new species (512.4/53.8 µm, in comparison to 204.4/36.5 µm in Ascoleuceta compressa and 274.6/53.7 µm in Ascoleuceta oentricosa ; Cavalcanti et al. 2013). Other differences are also present, such as the presence of microdiactines in Ascoleuceta oentricosa .

Te specimen SAMA S1917, collected in December 2015, is full of embryos and larvae. Cavalcanti et al. (2013) mentioned the presence of reproductive elements in the holotype of Ascoleuceta oentricosa , collected in April 2002 at 59 m depth.