Stylissa soestii sp. nov. Fig. 2 A–M Type Material. Holotype. NIOPor.3277.GA05, St George Island, south Goa, 15.11°N 73.77°E western Indian coast, SCUBA 9 m, coll. Anita M. George (AMG), 29 January 2020. Paratype. ZMAPor.17208, Hare Island, Gulf of Mannar, 9.19°N 79.08°E Tamil Nadu, southeast India, snorkelling 5 m, coll. AMG, 05 November 2000. Other material. NIOPor. 3277.GM03, Palk Bay, Palk Bay, 9.37°N 79.05°E Tamil Nadu, southeast India, snorkelling 3m; coll. Gowri, 09 May 2019. Etymology. Named after Dr Rob van Soest for his outstanding support to the author’s Indian sponge research, and for his monumental contribution to spongology as a whole. External morphology. Specimen erect, flabellate and planar with grooved surface; 10.8 cm width, 7 cm height and 5.2 cm thick (NIOPor.3277.GA05). Colour is reddish orange when alive (Fig. 2 A- in situ and 2B- ex situ) and grey when dried (Fig. 2C) (NIOPor.3277.GA05). The other two specimens (ZMAPor.17208, NIOPor.3277.GM03) also showed the same colour in situ and ex situ. The live specimens (holotype, paratype and the other material) are with smooth furrows while bits of the above dried specimens are rough in texture. Tough surface irregular and highly conulose. Conules 2 mm high. Oscules minute and abundantly scattered on the surface of collagenous membrane. Ostia are in the crests of the furrows. Skeleton. Choanosomal skeleton, irregular network, inseparable, matted and fibrous formed of irregular, straight and gently curved stout, stylote spicules, quite dense at some places and vacant in some areas (Fig. 2D). Extra-axial fibres arise from the axial part in an angle. The fibers are connected together in an ill-defined scalariform pattern. Extra-axial fibers in the surface look like toothbrush tips. Spicules. Megascleres. Styles of varied types (Figs 2 E–M): Five major types 1) Dominated, smooth, gently curved, stout styles (L: 421.9– 624.81 –785.16 µm, W: 10.65– 17.60 –26.37 µm; n=30) (Fig. 2E); 2) nearly straight, smooth, stout styles (L: 487.46– 532.1 –614.11 µm, W: 10.65– 23.94 –25.23 µm; n=14) (Fig. 2F); 3) abundant slender, smooth, and gently curved styles (L: 335.68– 500.09 –572.01 µm; W: 15.1– 11.13 –2.4 µm; n =25) (Fig. 2G); 4) abundant straight slender styles (L: 445.18– 545.20 –732.12 µm; W: 9.3– 10.5 –11.2 µm; n =25) (Fig. 2H); 5) hair/ thread-like flexuous and curved style (L: 315.27– 403.01 –720.9 µm; W: 7.59– 9.56 –14.95 µm; n=20) (Fig. 2I); and one minor type: 6) smooth slightly curved, centre-bulged, ‘pregnant-like’ strongyloxea (L:325.5– 441.93 – 544.42; W: 8.31– 14.07 –18.44 µm; n=7) (Fig. 2J). Also, few stout, strongyles (L:421.9–457.04–501.68 µm; W: 9.3–8.31–18 µm; n=3) (Fig. 2K) and thin oxeas (Fig. 2L) were probably contaminants or juvenile megascleres rarely found in this species. Both stout and slender styles have tapered tips with a blunt, rounded base; some have flattened, but rounded base. Some of the stout and slender styles (pregnant-like Fig. 2J) have an abrupt bend in the centre. A set of styles is shown in Fig. 2M. Distribution and Ecology. This species was found to be growing on rocky coral beds. The sponges were observed among turf algae on hard corals. The bright reddish orange colour is seen widely in St George Island, Goa. The region was dominated by reef fishes and gorgonians, Juncella juncea (Pallas, 1766). Remarks. Stylissa soestii sp. nov. is unique and differs from the type specimen (lectotype) of S. carteri (Dendy, 1889) collected from the Indian Ocean, Gulf of Mannar, by its varied types of styles, though the new species has the bright orange red colour that is similar to the other known species of Stylissa. Stylissa soestii sp. nov. possesses the major, curved stout styles (S. carteri: 400 x 21 µm, shorter than the new species), and gently curved slender, long styles (S. carteri: 1200 x 11 µm; longer than S. soestii sp. nov.). Additional types of styles include nearly straight, stout and slender styles, slender hair-like flexuous, and styles with a bulgy-centre. Moreover, when dried S. soestii sp. nov was grey while S. carteri remained dull reddish orange. Nevertheless, the irregular skeletal network of S. soestii sp. nov. with stylote spicules and no definite fibres matches that of S. carteri. The lectotype and paralectotype of S. carteri were examined by Alvarez & Hooper (2010), together with some other northern Australian species, and showed only a single type of styles (272–651 x 4–28 µm) with occasional strongylote modifications, differing from those of S. soestii sp.nov. Though the styles of S. flabelliformis (341–643 x 3–29 µm), redescribed from the Indonesian lectotype and paralectotype and abundant new material from northern Australia by Alvarez & Hooper (2010), also showed varied thickness – and thus closer to the new species – the absence of anisoxeas (255–596 x 6–27 µm), the presence of more than three types of styles in the new species from India, their respective morphologies, and their disjunct geographic distributions differentiate S. soestii sp. nov. from S. flabelliformis. Stylissa soestii sp. nov. also differs from S. massa from the Mergui Archipelago, Myanmar (Burma), the latter was grey or brown, massive, lobate and compressed and plumose while, S. soestii sp. nov. was bright reddish orange, soft and firm with a stout base, laminar, compressed and with grooved branches.

Published as part of George, Anita M., 2022, Tale of two species of Stylissa (Porifera: Demospongiae: Scopalinida) from the west and east coasts of India, pp. 72-80 in Zootaxa 5178 (1) on pages 74-76, DOI: 10.11646/zootaxa.5178.1.4, http://zenodo.org/record/7026027