Tethya muricyi Payne, Samaai & Gibbons, 2025

Payne, Robyn P., Samaai, Toufiek, Janson, Liesl, Kerwath, Sven E. & Gibbons, Mark J., 2025, Eleven new heteroscleromorph Demospongiae (Porifera), and a new record of the tetractinellid Ancorina corticata, from Walters Shoal, a shallow seamount on the Madagascar Ridge in the South West Indian Ocean (SWIO), Zootaxa 5575 (1), pp. 1-56 : 14-17

Tethya muricyi Payne, Samaai & Gibbons sp. nov.

urn:lsid:zoobank.org:act:28C01F6C-DBAF-4D85-A164-43A33F9B2AD9

Figure 5A–G , Table 3

Material examined. Holotype. SAMC-A096908 (cross-reference TS 2358 & WSL-INV94(30)): Walters Shoal Seamount, Grid WSL044 , Station ALG10976 , coll. RV Algoa , (33°14.0’ S; 43°55.5’ E) - (33°13.7’ S; 43°55.6’ E), 25–28 m depth, 02 June 2014 . Paratypes. SAMC-A096893 (cross-reference TS 2311 & WSL-INV50(2)), SAMC- A096896 (cross-reference TS 2327 & WSL-INV40): 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-A096899 (cross-reference TS 2337 & WSL-INV94(8)): Walters Shoal Seamount, Grid WSL044 , Station ALG10976 , coll. RV Algoa , (33°14.0’ S; 43°55.5’ E) - (33°13.7’ S; 43°55.6’ E), 25–28 m depth, 02 June 2014 . Additional material. TS 2349 ( WSL-INV94 (21)), TS 2352 ( WSLINV94 (24)): Walters Shoal Seamount, Grid WSL044, Station ALG10976, coll. RV Algoa , (33°14.0’ S; 43°55.5’ E) - (33°13.7’ S; 43°55.6’ E), 25–28 m depth, 02 June 2014. TS 2362 ( WSL-INV75 (3)), TS 2363 ( WSL-INV75 (4)), TS 2376 ( WSL-INV75 (17)): Walters Shoal Seamount, coll. RV Algoa , (33°11.2' S; 43°50.7' E), 29 m depth, 30 May 2014. TS 2420 ( WSL-INV24 (a)): Walters Shoal Seamount, Grid WSL021, Station ALG10953, coll. RV Algoa , (33°11.0’ S; 43°53.9’ E) - (33°11.0’ S; 43°52.9’ E), 43–53 m depth, 29 May 2014. TS 2430 ( WSL-INV119 (4)): Walters Shoal Seamount, coll. RV Algoa , (33°11.6' S; 43°50.5' E), 39 m depth, 05 June 2014. TS 2474 ( WSL-INV84 (3)), TS 2489 ( WSLINV84 (18)), TS 2493 ( WSL-INV84 (22)), TS 2496 ( WSL-INV84 (25)), TS 2498 ( WSLINV84 (27)): Walters Shoal Seamount, Grid WSL042, Station ALG10974, coll. RV Algoa , (33°11.2’ S; 43°51.0’ E) - (33°11.2’ S; 43°50.7’ E), 28–34 m depth, 02 June 2014. TS 2538 ( WSL-INV102 (4)): Walters Shoal Seamount, Grid WSL045, Station ALG10977, coll. RV Algoa , (33°13.8’ S; 43°56.1’ E) - (33°14.2’ S; 43°55.9’ E), 80 m depth, 02 June 2014.

Type locality. Walters Shoal Seamount , south of Madagascar on the Madagascar Ridge , Western Indian Ocean ( Fig. 1 ).

Description ( Fig. 5A ). Spherical to semi-spherical form. Length 1.6 cm and thickness 1.4 cm. Surface rough and fuzzy, but undulating and smooth in a couple of specimens. In other specimens, one (rarely two) oscules present on apex (~ 1 mm). Well-developed ectosome, ~ 1–2 mm thick, which is distinct but not separable from the choanosome. Texture tough, firm and dense. Not compressible, nor easily torn. Colour in life pale beige (with brown tinge) externally, olive green internally, with a white centre. In preservative, pale beige. Ectosome colour in life, and in preservative, white. Slightly sticky exudate present in a few specimens.

Skeleton ( Fig. 5B ). Choanosomal skeleton radial, comprising compact anisostrongyloxea and (aniso)strongyle (rare) tracts (~200 µm across) radiating from the centre of the sponge, often penetrating the ectosome as expanding dermal brushes, with megascleres piercing the sponge surface. Somewhat confused interstitial anisostrongyloxeas fill the space around the main megasclere bundles. Microscleres are common in the inner choanosome between the tracts. Thick, discernible ectosome (>1000 µm) comprised of small radial bouquets (~400–600 µm across) of megascleres embedded within this region, which pierce the sponge surface. Megasters (represented by spherasters) and micrasters are densely packed in ectosome, somewhat entering the upper regions of the choanosome, with the former decreasing in size from the sponge surface, inwards.

Spiculation ( Table 3 ). Megascleres. Primary and auxiliary anisostrongyloxeas, smooth, straight, thickest centrally, with reduced, somewhat elongate apices, often distally hastate, with no easily discernible size classes (continuous) and large size range: 639 (293–1280) × 11 (6–23) µm, n = 20 ( Fig. 5C ). Strongyles to anisostrongyles, relatively rare, smooth, straight, thickest centrally, often fusiform, with no easily discernible size class: 1020 (596– 1249) × 17 (9–25) µm, n = 20 ( Fig. 5D ). Microscleres. Megasters - spherasters with ~15 rays: 41 (21–56) µm, n = 20 ( Fig. 5E ). Micrasters - tylasters with ~11 terminally spined rays: 13 (10–15) µm, n = 20 ( Fig. 5F ); Spheroxyasters with ~8 rays: 6 (5–8) µm, n = 20 ( Fig. 5G ).

Substratum, depth range and ecology. Seventeen specimens found on rocky substratum in five sleds, in the lobster trap and during one dive. This species is found in association with tube worms, bivalves and algae in the form of epifauna. Depth range: 25– 170 m.

Etymology. The name ‘muricyi’ was given in honour of Dr Guilherme Muricy for his important contribution to the taxonomy, ecology and diversity of Brazilian sponges.

Remarks. The present material conforms well to Tethya Lamarck, 1815 , as diagnosed by a spherical form, well-developed, distinct ectosome and main skeleton formed by radiating strongyloxea bundles ( Sarà 2002). It is not conspecific with the nine species of Tethya that have been recorded from the WIO and South Africa: Tethya globostellata Lendenfeld, 1897 ; Tethya japonica Sollas, 1888 ; Tethya magna Kirkpatrick, 1903 ; Tethya parvistella ( Baer, 1906) ; Tethya peracuta ( Topsent, 1918) ; Tethya robusta ( Bowerbank, 1873) ; Tethya samaaii Ribeiro & Muricy, 2011 ; Tethya seychellensis ( Wright, 1881) and Tethya stellagrandis ( Dendy, 1916) (see Comparative measurements Table 3 ; de Voogd et al. 2024).

Tethya globostellata Lendenfeld, 1897 (anisostrongyloxeas: 1000–2100 × 24–32 µm; styles: 400–500 × 14– 16 µm; amphistrongyles: 1000–1500 × 33 µm; oxyasters: 60–100 µm; strongylasters: 9–12 µm) and T. parvistella ( Baer, 1906) (anisostrongyloxeas: 718–1342 × 3–18 µm; amphistrongyles: 841–1100 × 14–18 µm; spherasters: 33–59 µm; tylasters: I) 7 µm, II) 11 µm) somewhat resembles the present material. However, Tethya japonica and Tethya parvistella lack spheroxyasters, whereas Tethya globostellata , Tethya magna Kirkpatrick, 1903 , Tethya peracuta ( Topsent, 1918) , Tethya robusta , Tethya samaaii , Tethya seychellensis and Tethya stellagrandis have medium to large spheroxyasters, unlike the small spheroxyasters found in Tethya muricyi sp. nov. ( Table 3 ).

Figures

FIGURE 1. A) Map showing the location of Walters Shoal Seamount (red circle) within the bathymetric context of the Western Indian Ocean region (generated using QGIS v.2.6.1; available: qgis.osgeo.org/en/site/). B) Bathymetric map of Walters Shoal Seamount (generated using Surfer 9; Golden Software, available: www.goldensoftware.com). C) Bathymetric map of Walters Shoal Seamount (generated using Surfer 9; Golden Software, available: www.goldensoftware.com), with sled (S), dive (D) and lobster trap (LT) sampling locations.

FIGURE 5. External morphology, skeletal architecture and spicule complement of Tethya muricyi sp. nov. A—Lab photograph of whole-body image of preserved Holotype specimen. B—Skeletal architecture on transverse view showing radial architecture and scattered spherasters in choanosome. Spicule complement—C—Anisostrongyloxea. D—Strongyle. E—Spherasters. F— Tylaster. G—Spheroxyasters. Scale bars on figure.