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

AscoleuceTa parallela sp. nov.

( Figs 13, 14; Table 7)

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

Etymology: Fortheparallelchoanocytetubes(Latin = parallelus).

Diagnosis: Ascoleuceta subspherical to vasiform, with a single osculum. Cortex with very large and small triactines. Below the cortex, two choanocyte tubes fuse and run in parallel towards the atrium. Choanocyte tubes with small tetractines and some small triactines. Atrial skeleton composed mostly of small triactines, few very large triactines, and rare small and large tetractines. Boomerang spicules can be present.

Type material: Holotype, SAMA S1915, GAB, 33°20 ʹ 13″S, 130°15 ʹ 27″E, depth: 189 m, coll. GABRP, site IN2015 _ C02_395, 15 December 2015. GoogleMaps

Colour: Beige in ethanol ( Fig. 13A).

Morphology and anatomy: Sponge massive, sof, subspherical to vasiform, formed by regular and tightly anastomosed tubes surrounded by a continuous and smooth thin cortex ( Fig. 13A). Te osculum is apical, without ornamentations. Frequently, two inhalant tubes fuse and run as a single tube towards the atrium ( Fig. 13B), such that the tubes run in parallel, leaving empty spaces among them near the atrium. Te atrium is similar to a long and large tube, sinuous and covered by pinacocytes. Aquiferous system solenoid. Te choanocyte tubes are full of larvae ( Fig. 13B).

Te cortex is composed of large and small triactines ( Fig. 13C). Te choanocyte tubes have small triactines and tetractines, but tetractines are more abundant. Te apical actine of the tetractines are directed towards the lumen of the choanosomal tubes ( Fig. 13D). Te atrial skeleton has small triactines and a few large triactines, similar to those of the cortex ( Fig. 13E). Rare small tetractines are also found. Large tetractines were easily found in the spicule slides. Teir location in the sponge was not determined; however, in one section two of these spicules were found near the atrium. Triactines without one actine, i.e. diactines with a boomerang shape, were rare, such that they were not considered to be a separate category.

Spicules ( Table 7)

Large triactines: Regular (equiangular and equiradiate). Actines are conical, with sharp tips ( Fig. 14A). Te size of these spicules is very variable. Size: 420.5 (±119.3)/36.5 (±8.9) µm.

Large tetractines: Regular (equiangular and equiradiate). Actines are conical, with sharp tips ( Fig. 14B). Te size of these spicules is very variable. Size: basal, 265.8 (±44.7)/18.0 (±5.4) µm; apical, 229.7 (±38.2)/18.9 (±3.8) µm.

Small triactines: Regular (equiangular and equiradiate), but a few sagital spicules were also found. Actines are cylindrical, with blunt tips ( Fig. 14C). Size: 128.8 (±19.8)/8.2 (±1.2) µm.

Small tetractines: Regular (equiangular and equiradiate), but a few sagital were also found. Actines are cylindrical, with blunt tips ( Fig. 14D). Te apical actine is very thin (needle-like) and sharp, curved or straight but frequently undulated. It is smooth ( Fig. 14D). Size: basal, 131.9 (±14.6)/8.3 (±0.7) µm; apical, 79.7 (±24.1)/3.6 (±1.0) µm.

Geographical distribution: Currently known from only the type locality in the GAB.

Ecology: Tis species was found at a depth of 189 m on the edge of the continental shelf (in fine sand and silt).

Remarks: Ascoleuceta parallela is very similar to the other species of Ascoleuceta found in the GAB; however, this was the only species in which large tetractines (possibly from the atrial skeleton) were found in addition to boomerang spicules, i.e. triactines that have lost one of their actines. Tis species had conspicuous parallel tubes; however, as the sponge was reproducing, we cannot be sure whether the organization of the tubes is the result of reproduction. Considering these characters, this new species is differentiated from all other species of Ascoleuceta .

Curiously, boomerang spicules were also found in Leucascus boomerang , which draws atention to this type of spicule being present in at least two different genera of Calcinea from the GAB. Some species of Rowella also have pygmy triactines with one reduced actine, described as ‘V-shaped’ by Lopes and Klautau (2023). Grantessa boomerang ( Dendy, 1893) (Calcaronea) also contains boomerang spicules in its skeleton. Dendy (1893) considered them to be bent diactines, whereas in Ascoleuceta parallela , Leucascus boomerang , and Rowella spp. boomerang spicules are modified triactines with one reduced actine.