Leucascus polynesiensis Lopes, Pérez & Klautau, 2024, sp. nov.

Leucascus polynesiensis sp. nov. (Figs 9, 10; Table 4) Zoobank registration: urn:lsid:zoobank.org:act: 6735AAAE-487B-4DF8-97A0-EC2A03CED440. Type species: Leucascus simplex Dendy, 1892. Synonyms: Leucascus simplex Dendy, 1892 — Klautau et al. 2013: 454, Klautau et al. 2020: 277. Leucetta chagosensis Dendy, 1913 — Hall et al. 2013: 500. Calcarea sp — Pérez et al. 2016: 304. Diagnosis: Beige Leucascus with subspherical cormus. Skeleton composed of slightly conical and sharp triactines and tetractines. Triactines are the most abundant spicules in the cortex and choanosome. In the atrium, tetractines are the most abundant. Apical actine of the tetractines needle-like always covered with short spines. Etymology: For its area of occurrence, i.e. French Polynesia. Type locality: Hakaheteau cave, Ua Pou, Marquesas, French Polynesia. Type material: Holotype: French Polynesia, Marquesas Islands, Ua Pou: UFRJPOR 7520, Hakaheteau cave (9°23.7 ʹ S, 140°07.7 ʹ W), 10 m depth, 23.i.2012, coll. T. Pérez, field number MQ24- GR-TP05. Paratype: French Polynesia, Society Islands, Tahiti Island: UFRJPOR 6451 = MNHN-IP-2018-22, Station ST12 (17°31.3 ʹ S, 149°33.4 ʹ W), 10 m depth, 23.iii.2009, coll. C. Débitus. Other material examined: Marquesas Islands: UFRJPOR 6456 = MNHN-IP-2018-27, Station MHO05, Hiva Oa (9°42.553 ʹ S, 139°01.18 ʹ W), 15 m depth, 8.ix.2009, coll. C. Débitus, field number P167. UFRJPOR 7518, Matautu cave, Fatu Hiva (10°28.3 ʹ S, 138°40.6 ʹ W), 25 m depth, 17.xii.2012, coll. T. Pérez, field number MQ15-GR-TP04. Society Islands: UFRJPOR 6458 = MNHN-IP-2018-29, Station M01, Moorea (17°29.681 ʹ S, 149°51.717 ʹ W), 8 m depth, 0. xii.2010, coll. C. Débitus, field number P221. UFRJPOR 8919 = MNHN-IP-2018-60, Station ST52, Tahiti, (17°47.147 ʹ S, 149°25,359 ʹ W), 30 m depth, 21.iv.2013, coll. S. Petek, field number P480˗ST52. UFRJPOR 8921 = MNHN-IP-2018-62, Station ST27, Tahiti (17°46.642 ʹ S, 149°24.236 ʹ W), 20 m depth, 12.iv.2013, coll. S. Petek, field number P480˗ST27. . 2018 Voogd De and Soest Van From * Colour: Light beige in life and in ethanol (Fig. 9A–C). Description: Sponge subspherical with one or two apical oscula surrounded by a membrane, sometimes more than one ‘sphere’ connected (Fig. 9A–C). A smooth cortical membrane covers the tubes (Fig. 9D). Anastomosis tight and regular. Atrium surrounded by endopinacoderm, with evident excurrent canals. Aquiferous system solenoid. Skeleton of the cortex and tubes composed mainly of triactines and few tetractines. Tubes predominantly smooth, but occasionally tetractines project their apical actines into the lumen (Fig. 9E). Atrial skeleton composed of few triactines and abundant tetractines (Fig. 9F). Spicules (Fig.10; Table 4) Triactines: Regular to subregular. Actines slightly conical, with sharp tips (Fig.10A). Size(UFRJPOR 7520): 107.0 (±14.7)/9.8 (±1.0) µm. Tetractines: Regular to subregular. Actines slightly conical, with sharp tips (Fig. 10B, C). The apical actine is very thin (needle-like), cylindrical and sharp, almost entirely covered with short spines (Fig. 10C). Size (UFRJPOR 7520): 106.0 (±8.7)/9.4 (±1.0) µm (basal); 76.9 (±22.0)/4.9 (±0.4) (apical) µm. Ecology: This species was collected inside and outside underwater caves. Recorded depth range: 8 to 10 m (Klautau et al. 2020; present study). Geographical distribution: Society Islands (Klautau et al. 2020) and Marquesas Archipelago (Hall et al. 2013, Klautau et al. 2020; present study), French Polynesia. Ecoregions: Society Islands and Marquesas. Remarks: The specimens analysed are morphologically very similar to those described by Klautau et al. (2020), also from French Polynesia. The identification of the specimens from that work as Leucascus simplex was, in our opinion, incorrect. According to Dendy (1892) and Cavalcanti et al. (2013), the skeleton of Leucascus simplex is composed of abundant triactines and rare tetractines, while in the specimens from French Polynesia, tetractines are not rare and are even more abundant than the triactines in the atrial skeleton. Hence, we consider the French Polynesian specimens, described in the present work and by Klautau et al. (2020), as a new species. Moreover, we propose that the records of Leucascus simplex in French Polynesia belong to the new species Leucascus polynesiensis. Besides Leucascus simplex and Leucascus polynesiensis sp. nov., other Leucascus with only one category of triactines and tetractines are Leucascus flavus, Leucascus neocaledonicus, and Leucascus roseus Lanna et al., 2007. The cormus of Leucascus neocaledonicus is amorphous, lobate, and folded, while the new species is almost spherical. Besides, Leucascus neocaledonicus has conical actines, while they are slightly conical in Leucascus polynesiensis sp. nov., and the new species has more tetractines than triactines in the atrial skeleton, while in Leucascus neocaledoni c us triactines are more abundant. The length of the spicules is very similar between the two species; however, they are thicker in Leucascus neocaledonicus [triactines: 102.9 (±21.4)/14.2 (±3.1) µm; tetractines: 103.2 (±12.6)/14.1 (±2.1) µm (basal); 45.2 (±3.0)/4.4 (±0.1) µm (apical; Cavalcanti et al. 2013)] than in Leucascus polynesiensis sp. nov. [triactines: 107.0 (±14.7)/9.8 (±1.0) µm; tetractines: 106.0 (±8.7)/9.4 (±1.0) µm (basal); 76.9 (±22.0)/4.9 (±0.4) µm (apical)]. Like in Leucascus polynesiensis sp. nov., tetractines are more abundant in the atrial region of Leucascus roseus. Nevertheless, Leucascus roseus is pink alive, and the actines of its spicules are cylindrical and blunt, differing from the beige colour and slightly conical and sharp spicules of Leucascus polynesiensis sp. nov .. Considering the spicules size, Leucascus roseus has relatively smaller and thinner spicules [triactines: 92.5 (±11.6)/7.3 (±1.5) µm; tetractines: 92.7 (±8.4)/7.3 (±0.9) µm (basal); 51.2 (±14.2)/3.3 (±0.9) µm (apical; Lanna et al. 2007)] when compared to Leucascus polynesiensis sp. nov .. Leucascus flavus is the most similar species to Leucascus polynesiensis sp. nov .. However, Leucascus flavus is yellow alive, amorphous, and lobate, while the new species is beige and subspherical. Besides, triactines and tetractines are present in the same proportion in the choanosome of Leucascus flavus, while in Leucascus polynesiensis sp. nov. triactines are more abundant. Leucascus flavus and Leucascus polynesiensis sp. nov. are also closely related in the C-LSU phylogenetic tree: they are sistertaxa with high support value (BS = 100%), but recovered in distinct clades.