Penares waltershoalensis Payne, Samaai & Gibbons 2025, sp. nov.

Penares waltershoalensis Payne, Samaai & Gibbons sp. nov. urn:lsid:zoobank.org:act: 58A654F1-3650-4C30-A957-2FAF574DE4FB Figure 4A–J, Table 2 Material examined. Holotype. SAMC-A096918 (cross-reference TS 2447 & WSL-INV74(13)): Walters Shoal Seamount, Grid WSL024, Station ALG10956, coll. RV Algoa, (33°08.8’ S; 43°49.1’ E) - (33°09.0’ S; 43°50.5’ E), 103–348 m depth, 29 May 2014. Paratypes. SAMC-A096887 (cross-reference TS 2300 & WSL-INV58), SAMC-A096890 (cross-reference TS 2307 & WSL-INV57(2)): Walters Shoal Seamount, Grid WSL022, Station ALG10954, coll. RV Algoa, (33°10.9’ S; 43°48.6’ E) - (33°11.2’ S; 43°50.2’ E), 72–170 m depth, 29 May 2014. SAMC-A096917 (cross-reference TS 2445 & WSL-INV74(11)): Walters Shoal Seamount, Grid WSL024, Station ALG10956, coll. RV Algoa, (33°08.8’ S; 43°49.1’ E) - (33°09.0’ S; 43°50.5’ E), 103–348 m depth, 29 May 2014. Additional material. TS 2314 (WSL-INV51): Walters Shoal Seamount, Grid WSL022, Station ALG10954, coll. RV Algoa, (33°10.9’ S; 43°48.6’ E) - (33°11.2’ S; 43°50.2’ E), 72–170 m depth, 29 May 2014. TS 2446 (WSL-INV74 (12)), TS 2451 (WSL-INV74 (17)), TS 2454 (WSL-INV74 (20)), TS 2548 (WSL-INV74 (30)), TS 2555 (WSL-INV74 (37)): Walters Shoal Seamount, Grid WSL024, Station ALG10956, coll. RV Algoa, (33°08.8’ S; 43°49.1’ E) - (33°09.0’ S; 43°50.5’ E), 103–348 m depth, 29 May 2014. Type locality. Walters Shoal Seamount, south of Madagascar on the Madagascar Ridge, Western Indian Ocean (Fig. 1). Description (Fig. 4A). Thickly encrusting form. Length 1.5 cm, width 1.7 cm and thickness 0.3 cm. Surface undulating but smooth with oscules (<1 mm) scattered randomly over the surface. Thin cortex (<1 mm) present, separable from the choanosome. Texture firm, tough, dense and leathery. Specimen not compressible, easily torn. Colour in life dull orange-brown externally and internally, pale olive green in preservative. Skeleton. Confused choanosomal skeleton, comprising of oxeas and microxeas arranged in a disorderly fashion (spicules distributed randomly), showing little tendency to form tracts (Fig. 4B). Larger oxeas sometimes aggregating in loose (somewhat radial) slanting bundles (~60–140 µm across). Dichotriaenes form subdermal skeleton, with cladome at surface and rhabdome inwards. Oxyasters abundant and scattered throughout. Ectosomal skeleton comprised of small oxeas, lying tangentially over dichotriaene clads, forming dense dermal crust ~200– 300 µm thick (Fig. 4C). Spiculation (Table 2). Megascleres. Oxeas, slightly curved, in three size classes: I) Large, 801 (703–999) × 27 (21–37) µm, n = 20 (Fig. 4D); II) medium, 393 (318–546) × 19 (15–22) µm, n = 25 (Fig. 4E); III) small, 143 (118–186) × 9 (7–12) µm, n = 20 (Fig. 4F). Dichotriaenes (Fig. 4G, H), with short rhabdomes, in two size classes: I) rhabdome not seen (~half the size of the cladome) [TS 2307 rhabdome, 134 (49–201) × 29 (20–39) µm, n = 6)], cladome 485 (381–579) µm, stout protoclads 101 (68–124) × 36 (28–49) µm, deuteroclads, often irregular at tips 141 (116–178) × 28 (20–39) µm, n = 20; II) rhabdome not seen (~half the size of the cladome) [TS 2307 rhabdome, 89 (40–133) × 24 (14–31) µm, n = 7)], cladome 338 (226–481) µm, thin protoclads 90 (75–108) × 20 (14–27) µm, deuteroclads terminating in sharp points 67 (28–123) × 14 (7–19) µm, n = 20. Microscleres. Microxeas (Fig. 4I), curved: 77 (63–99) × 6 (5–7) µm, n = 20. Acanthoxyasters with ~16 slender rays, hooked spines and sharply pointed tips: 9 (8–12) µm, n = 20 (Fig. 4J). Substratum, depth range and ecology. Ten specimens found on rocky substrata in two sleds, one consisting of predominantly bivalves and sponges, the other of biogenic debris and hydrozoans. Depth range: 72– 348 m. Etymology. Named for the type locality and known distribution of this species, Walters Shoal Seamount. Remarks. Sponges in the genus Penares are typically irregularly massive, cream, grey or black in live colouration, and are characterised by a thin cortex comprised of smooth microxeas or microrhabds, and short-shafted plagio-, dicho- or orthotriaenes (Sim-Smith & Kelly 2019). The genus Penares currently includes 44 valid species (de Voodg et al. 2024), which are found in temperate and tropical waters of the world, from the intertidal to depths of more than 1000 m (Sim-Smith & Kelly 2019). Only three species have been described from temperate southern Africa, the WIO, and the West and South Indian Shelf Provinces. Penares orthotriaena Burton, 1931 was recorded from the Natal and Delagoa ecoregions, whilst Penares schulzei (Dendy, 1905) and Penares intermedius (Dendy, 1905) were described from South India and Sri Lanka. Penares schulzei (Dendy, 1905) has been recorded in New Caledonia and New Zealand by Sim-Smith & Kelly (2019), expanding its range to the tropical southwestern Pacific and northern New Zealand ecoregion. These species will be compared with the present material. Penares orthotriaena Burton, 1931 described from the mouth of the uThukela and Umvoti Rivers (Natal ecoregion) at a depth of 64 m, is a massive sponge possessing orthotriaenes with a straight rhabdome, biangulate microstrongyla and tylasters (see Fig. 1 in Burton (1931)). Lévi (1964) recorded the species from Mozambique. However, Lévi's sample (see Fig. 7 in Lévi (1964)) lacks orthotriaenes, biangulate microstrongyla, and tylasters present in the holotype. Lévi's sample is more similar to the undescribed new species described here, based on the spicule complement in Fig. 7, although Lévi (1964) provides little information. Penares intermedius (Dendy, 1905) collected in waters 182 m deep, 12 miles off the coast of Galle, Sri Lanka (Dendy 1905), is an irregularly branched and shortly stalked nodose sponge, spreading more or less horizontally, and rounded at the extremities. Pulitzer-Finali (1993) identified a specimen from North Kenya Banks, Kenya (110 m) as P. intermedius, noting the presence of short-shafted triaenes, large oxeas and smooth oxyasters similar to those observed in the holotype. Pulitzer-Finali (1993) found that smaller oxeas had a continuous graduation between the smaller oxeas, with a size range from 75–410 µm. Dendy (1905) also said that, “ varying very much in size; averaging, say, about 0.18 millim. by 0.01 millim, but ranging from about a third of these dimensions through intermediate sizes to the large forms. Thomas (1984) identified a specimen collected from Sri Lanka as Penares intermedius (Dendy, 1905). Thomas noted “minutely spined or not” oxyasters in his specimen. Dendy (1905) and Pulitzer-Finali (1993) did not mention minutely spined oxyasters, which may be due to the fact that the spines may only be visible with a scanning electron microscope. This could explains the (slightly larger) ‘smooth’ oxyasters given in the original description of P. intermedius (Dendy, 1905) when viewed through a light microscope. However, we cannot confirm this, as we have not studied the holotype of P. intermedius. The comparative spicule dimensions for the specimens of Dendy (1905), Pulitzer-Finali (1993) and Thomas (1984) are as follows: Penares intermedius (Dendy, 1905) originally described as Plakinastrella intermedia (oxeas: I) 1200 × 37 µm, II) 180 x 10 µm; dichotriaenes: rhabdome 370 × 55 µm, with protoclads 92 × 55 µm; oxyasters: 25 µm) and further records of this species by Pulitzer-Finali (1993) (oxeas: I) 1000–1500 x 33–62 µm, II) 75–410 × 5.5–22 µm; dichotriaenes: rhabdome 190 µm, protoclads 95 µm, deuteroclads 160 µm; Oxyasters: 12–23 µm) and Thomas (1984) (oxeas: I) 790 x 30 µm, II) 190 × 6–12 µm; dichotriaenes: protoclads 80 × 50 µm, deuteroclads 280 × 5 µm; oxyasters: 18 µm). Although Dendy (1905) only described one size class of dichotriaenes for P. intermedius (Table 2), he does make note of ‘slenderer’ forms which he suggests are not fully developed. In addition, while providing two size classes of oxeas, he notes a large size range (Table 2). Our specimen has a clear size separation between the oxeas and has heavily spined oxyasters that are much smaller than those of P. intermedius (Table 2). The thinly encrusting form, spicule dimensions and spined oxyasters of the new species described here differ substantially from the holotype of P. intermedius (Plate I, Fig. 4; Plate II, Fig. 2 in Dendy (1905)) and the Kenyan specimen (Pulitzer-Finali 1993). Dendy (1905) reported a second species, Penares schulzei (Dendy, 1905), off the coast of Galle, Sri Lanka, in the same locality and station as Penares intermedius. Burton (1959) proposed that Plakinastrella (now Penares) schulzei (Dendy, 1905) is conspecific with P. intermedius, based on similarities in the figures drawn (see Plate II, Figs. 2 & 3 in Dendy (1905)) and a re-examination of the holotypes. This suggestion was accepted by Thomas (1984), but ignored by Pulitzer-Finali (1993). Burton (1959) recorded the species from Zanzibar at depths ranging from 75 to 165 m. Lévi & Lévi (1983) and Sim-Smith & Kelly (2019) regarded Penares schulzei as a valid species. This is based on specimens collected from New Caledonia and New Zealand, respectively. Penares schulzei and P. intermedius continue to be identified separately in the World Porifera Database (de Voogd et al. 2024). The specimen described by Lévi & Lévi (1983) had smooth oxyasters with 6–8 actines and a diameter of 20–30 µm. The holotype has short-shafted dichotriaenes (Dendy, 1905 Plate II, Fig. 3) resembling calthrops with a total diameter of 680 µm. Similar to Penares intermedius, Lévi & Lévi (1983) may not have been able to determine if the oxyasters are lightly spined because they observed the spicules under a light microscope. However, we cannot confirm this, as we have not studied the holotype of P. schulzei. The New Zealand specimen (NIWA 75616) (Sim-Smith & Kelly 2019) has spined oxyasters and a noticeable size separation between the oxeas and microxeas, which differs from the holotype of Penares schulzei. Thomas (1984) found spined oxyasters in a specimen that he identified as