Robspongia vociva, Klautau & Lopes & Tavares & Rizzieri & Sorokin & Fromont & Goudie & Crowther & McCormack & George & Wahab, 2025

Robspongia vociva View in CoL gen. nov., sp. nov.

( Figs 5, 6; Table 3)

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

Etymology: From Latin oocious, meaning void, to reinforce the absence of spicules in the choanosome and atrium.

Diagnosis: Robspongia with fusiform microdiactines, triactines, and tetractines, most of them parasagital. Cells with brown inclusions are present.

Type material: Holotype, SAMA S1859, GAB, 35°02 ʹ 17″S, 134°05 ʹ 42″E, depth: 221 m, coll. GABRP, site IN2015 _ C02_128, 4 December 2015. GoogleMaps

Colour: Brown in ethanol ( Fig. 5A).

Morphology and anatomy: Tere are several specimens of this species. Sponge delicate, individual tube tapering from the top to the base, but not forming a peduncle ( Fig. 5A). Te osculum is single and apical without a crown ( Fig. 5B). Te holotype, which is 7.5 cm high, has a very thin body wall ( 0.08 cm thick) when compared with the central cavity ( 0.5 cm wide). Asconoid aquiferous system ( Fig. 5C). Cells with brown inclusions are present.

Te skeleton is composed of cortical tangential triactines and tetractines that project their long apical actines into the choanosome, frequently reaching the central cavity, which is hispid in consequence ( Fig. 5C, D). Tere are also few tangential microdiactines ( Fig. 5E). Tere is no other kind of skeleton.

Spicules ( Table 3)

Microdiactine: Fusiform, with sharp tips, straight or bent in one tip, smooth ( Fig. 5E). Size: 48.3 (±8.5)/1.0 (±0.1) µm.

Triactine: Frequently parasagital (equiangular but with a longer unpaired actine); however, regular (equiangular and equiradiate) spicules can also be found. In the parasagital spicules, one of the paired actines is frequently shorter than the other. Te longest paired actine was always measured. Actines are cylindrical, with sharp or blunt tips ( Fig. 6A). Size: paired actine, 212.2 (±38.1)/13.4 (±1.0) µm; unpaired actine, 280.7 (±74.3)/13.4 (±1.4) µm.

Tetractine: Frequently parasagital (equiangular but with a longer unpaired actine), although regular (equiangular and equiradiate) spicules can also be found. Te basal actines are straight, but they can also be curved. Tey are cylindrical and sharp or blunt ( Fig. 6B). Te apical actine is cylindrical, smooth, and sharp, very long, frequently curved, but sometimes straight ( Fig. 6C). It is common to find undulated apical actines. Size: paired actine, 246.5 (±31.8)/20.2 (±4.8) µm; unpaired actine, 322.6 (±77.6)/21.6 (±5.8) µm; apical actine, 662.7 (±148.6)/21.1 (±1.7) µm.

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

Ecology: Tis species was found at a depth of 221 m on the edge of the continental shelf (in fine sand and silt).

Taxonomic remarks: Robspongia is morphologically very similar to Soleneiscus Borojević, Boury-Esnault, Manuel & Vacelet, 2002 , and in the C-LSU phylogeny they are sister groups, although with very low support (bootstrap = 62%). Te main difference between the new genus and Soleneiscus is in the organization of the body. Soleneiscus has several ascon tubes growing from stolon-like tubes or tubes are ramified, whereas in the new genus the body is a single tube.

Robspongia oocioa formed a highly supported clade (bootstrap = 100%) with a specimen from Tasmania identified as Ascandra sp. by Voigt et al. (2012, 2018; QM G323326). Te analysis of pictures of that specimen (supplementary material of the paper by Voigt et al. 2012) indicated that it is also solitary and brown in ethanol and has large tetractines, with the apical actine penetrating the atrium. It is possible that it represents the same species described here. Te specimen from Tasmania was collected at 195.8 m depth. Another specimen, also deposited at the Queensland Museum (QM G326171) and collected in Tasmania, but with depth ranging from 370 to 410 m, which was analysed by pictures, is likewise probably Robspongia oocioa .

Ascandra minchini Borojević, 1966 View in CoL is the only species of Ascandra View in CoL formed by a single tube. Considering its morphology, Ascandra minchini View in CoL is probably a species of Robspongia View in CoL , hence we reallocate it to the new genus Robspongia View in CoL . It is interesting to highlight that Robspongia minchini comb. nov. has microdiactines at the outer surface, as does Robspongia oocioa . Both species can be differentiated from each other mainly by the shape of the microdiactines, which are fusiform in the new species and with a protuberance in the middle, and by the thickness of all the spicule categories, which are always thicker in Robspongia minchini comb. nov. [microdiactines, 120–150/5–10 µm; triactines, 150–350/10–25 µm; tetractines (basal), 200– 400/15–40 µm; apical, 400–800/30–40 µm].