Xestospongia dorigo Rocha & Moraes & Salani & Hajdu 2021, sp. nov.
Creators: name: Rocha, Lívia
name: Moraes, Fernando
name: Salani, Sula
name: Hajdu, Eduardo
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Demospongiae
Haplosclerida
Petrosiidae
Xestospongia
Xestospongia dorigo

description: Xestospongia dorigo sp. nov.   
(Fig. 1, 7; Tab. 7)  
 Holotype. Brazil, Alagoas State, MNRJ 15405, Francês Beach (9.76725º S, 35.83610º W, Marechal Deodoro), 2.9 m depth, Col. E. Hajdu, 2011.9.15. Paratypes (two specimens). Ceará State, MNRJ 20131, Boi Choco Beach (03.68753º S, 38.61034º W, Dois Coqueiros, Caucaia), 1 m depth, Col. A. Bispo & S. Salani, 2016.4.11. Alagoas State (type locality), MNRJ 21029, 2– 4 m depth, Col. A. Bispo, 2016.12.19.   
 Diagnosis. This is the only Tropical Western Atlantic Xestospongia with a cushion-shape, no projections, with relatively small oscula (2–3 mm diam.), and white to beige colour in vivo. Megascleres are oxeas with acerate, hastate and mucronate ends, 300–450/ 5–15 µm.   
 External morphology. Cushion-shaped, up to 12 cm in diameter (Fig. 7A–B). Surface smooth to the naked eye, irregular, without any marked projections, but rough to the touch. Rare, circular oscules (2–3 mm diam.). Consistency firm, slightly compressible, and fragile. Colour in vivo light yellowish-white (holotype), light grayish-brown (MNRJ 20131), or light yellowish-beige (MNRJ 21029), becoming a light shade of gray or beige after fixation.   
 Skeleton. Ectosomal, an isodyctial, isotropic reticulation (Fig. 7C) with uni- to paucispicular tracts (up to 63 µm thick), forming (sub)triangular meshes (65–195 µm wide). Choanosomal, similar, but denser than the ectosomal, tracts 30–90 µm thick, meshes 110–230 µm wide (Fig. 7D); aquiferous canals seen here and there (520–1,775 µm wide).   
 Spicules. Oxeas in a single size class, smooth, slightly curved, with hastate, acerate and mucronate edges: 294–369 (22)–445/ 5–10 (2)– 15 µm (Fig.7E–F; Tab.7).   
 Ecology. The species occurs in association with other sponge species, tunicates, ophiuroids and mollusks, between 1 and 4 m depth.   
 Etymology. The specific epithet is used as a noun in apposition, and honors Prof. Dr. Monica Dorigo Correia, prematurely deceased, a long-time collaborator and friend of the authors.   
 Type locality. Marechal Deodoro (Francês Beach), Alagoas State, Brazil. Additional distribution. Provisional Brazilian endemic, also known from Ceará State (Caucaia).   
 Taxonomic remarks. There are only 11 shallow and relatively shallow-water species of Xestospongia in the Tropical Western Atlantic (see Carvalho et al. 2016). These include X. deweerdtae, X. portoricensis Van Soest, 1980 and X. rampa de Laubenfels, 1934 (the latter deemed to be a junior synonym of X. muta by Zea 1987), which possess strongyles instead of oxeas as their megascleres; as well as X. bocatorensis Diaz et al., 2007, which possesses sigma microscleres. All four species are regarded quite distinct from X. dorigo sp. nov. Considerably smaller spicules than seen in X. dorigo sp. nov. differentiate X. menzeli Little, 1963 from our new species as well.   
 The remaining five species are X. arenosa van Soest & de Weerdt, 2001, X caminata Pulitzer-Finali, 1986, X. muta (Schmidt, 1870), X. purpurea Rützler, Piantoni, Van Soest & Diaz, 2014 and X. wiedenmayeri van Soest, 1980. Xestospongia arenosa was originally reported as comprising “clusters of short irregular tubes and closed digitations, and smaller fistules rising from a massive base, which is usually entirely covered by sediment, rubble and shells” (cf. Van Soest & de Weerdt 2001). Overall, this habit is notoriously distinct from the nearly flat, only thickly encrusting habit observed in X. dorigo sp. nov., which, furthermore possesses only rare, rather small (2–3 mm diam.) oscula, contrasting to the large oscula (up to 15 mm diam.) reported for X. arenosa (van Soest & de Weerdt 2001, Rützler et al. 2014, Silva & Zea 2017). Xestospongia caminata usually has a smooth surface and large (5–9 mm diam.) oscula, bearing megascleres of varied form, mostly oxeas, but ranging to styles and strongyles. Its megascleres were reported to be considerably smaller (200–280 µm, Pulitzer-Finali 1986) than those in X. dorigo sp. nov., but a subsequent record of the species by van Soest & de Weerdt (2001) found megascleres as large as 370 µm, thus approaching the size of spicules seen in the new species. However, we consider the sponge habit sufficiently characteristic to preclude their possile cospecificity, strenghtened by the fact that X. caminata is reported to be dark coloured in vivo, while X. dorigo sp. nov. is light-coloured. Xestospongia muta, known as the great-barrel sponge, is markedly distinct from the new species, even when quite young, for its purplish-rose colour in vivo. Besides, the strongyles present in the majority of Brazilian specimens studied, which on one side are only occasionally modified into strongyloxeas, and on the other are much stouter (with the means of spicule widths being around 18 µm), support differentiating the two species. Xestospongia purpurea, in addition to its distinctive spotted purple colour in vivo, has much stouter megascleres, thus appearing quite distinct from the new species too. Megasclere thickness is well known to be directly dependent on proximity from continental sources of silica in the wider Caribbean region (e.g. Zea 1987), and accordingly, this is a character to be looked at cautiously. In the case of X. purpurea, both records are from continental sites (Belize and Cartagena; respectively Rützler et al. 2014; Silva & Zea 2017), optimal surrogates for the confirmation of the species’ ability to produce thicker spicules. As X. dorigo sp. nov. also occurs in coastal and supposedly silica rich waters (Ceará and Alagoas States), we consider the distinctness of both species ability to build thick spicules to be of diagnostic importance. Lastly, X. wiedenmayeri approaches the new species considerably. Points of distinction are the presence of cylindrical projections and hollow fistules, the dark brownish-red colour in the fixative, and somewhat thicker oxeas of the latter species from Curaçao. Given the above comparisons, we are confident that X. dorigo sp. nov. is a new species.
description: Published as part of Rocha, Lívia, Moraes, Fernando, Salani, Sula & Hajdu, Eduardo, 2021, Taxonomy of Petrosiidae Van Soest, 1980 (Haplosclerida, Porifera) from Brazil, pp. 251-287 in Zootaxa 5004 (2) on pages 279-280, DOI: 10.11646/zootaxa.5004.2.2, http://zenodo.org/record/5677189