Sponges (Demospongiae, Poecilosclerida) from New Deep-sea Frontiers in the Southwestern Atlantic: New Species, New Combinations and Taxonomic Remarks on Echinostylinos

© 2024 Academia Sinica, Taiwan Open Access Sponges (Demospongiae, Poecilosclerida) from New Deep-sea Frontiers in the Southwestern Atlantic: New Species, New Combinations and Taxonomic Remarks on Echinostylinos Cristiana Castello-Branco1,2,* and Eduardo Hajdu2 1Smithsonian Institution, National Museum of Natural History, 10th and Constitution Ave NW, Washington, DC 20560-0163, United States of America *Correspondence: E-mail: [email protected] (Castello-Branco) 2Museu Nacional, Universidade Federal do Rio de Janeiro, Quinta da Boa Vista s/n, 20940-040, Rio de Janeiro, RJ, Brazil. E-mail: eduardo. [email protected] (Hajdu) urn:lsid:zoobank.org:pub:22347C6C-25A7-4C08-B837-6107A821DC44 Received 15 September 2022 / Accepted 9 September 2024 / Published 31 December 2024 Communicated by Benny K.K. Chan Echinostylinos comprises 11 species, among which a single, recently reported record for the South Atlantic. Here we propose two further new species from this ocean basin. Echinostylinos iatapiuna sp. nov. (2300‒3200 m depth, São Paulo Ridge) and Echinostylinos abyssalis sp. nov. (4008 m depth, São Paulo Ridge). The latter pushes the genus’ known distribution into the abyssal zone for the first time. The morphologic variation observed in the microscleres of Echinostylinos is briefly discussed, motivating our proposal to transfer Echinostylinos glomeris (Topsent, 1904, as Esperiopsis) to Abyssocladia, a stipitate or likely so, which compound with chelae of cleistochelae morphology to point to the latter genus as its best assignment. An identification key for Echinostylinos spp. is offered (now 13). In addition, a new species of Chondrocladia is described, namely Chondrocladia (Chondrocladia) trisigmata sp. nov. (3250–3270 m depth, south of the Vitória-Trindade seamounts’ chain). Finally, some biogeographic considerations are made about abyssal sponge records in the South Atlantic. Key words: Porifera, Shinkai, MD55, Abyssal fauna, Bathyal fauna, Manned submersible, South Atlantic, Carnivorous sponges Citation: Castello-Branco C, Hajdu E. 2024. Sponges (Demospongiae, Poecilosclerida) from new deep-sea frontiers in the southwestern Atlantic: new species, new combinations and taxonomic remarks on Echinostylinos. Zool Stud 63:46. doi:10.6620/ZS.2024.63-46. BACKGROUND The southwestern Atlantic is characterized by prominent topographical features such as the VitóriaTrindade seamounts chain, the São Paulo Ridge and the Rio Grande Rise. The Vitória-Trindade seamounts chain is located offshore Brazil’s eastern coast (off Espírito Santo state) and is characterized by a longitudinally oriented linear ridge, approximately 950 km long at the latitude of 20°30'S (Motoki et al. 2012). The Franco-Brazilian expedition “TAFF MD55/Brazil 1987” sampled along these seamounts on board the R/V ‘Marion Dufresne’ in depths of 15 to 5100 meters (Tavares 1999), and most of the Porifera collection of this expedition had been untouched until recently (Tabachnick et al. 2009; Castello-Branco et al. 2016). The São Paulo Ridge is about 350 km long at the latitude of 28–29°S, and is located between the São Paulo Plateau, and the Vema Channel (off S and SE Brazil). It comprises a linear submarine chain with about 220 km extension, and bathymetric range between 2000 and 4400 m depth (Bassetto et al. 2000; Goto et al. 2017; Perez et al. 2020). In 2013, a Japanese-Brazilian scientific research expedition, ‘Iata-Piuna’, onboard the JAMSTEC R/V ‘Yokosuka’, along with the manned submersible ‘Shinkai’, sampled along the São Paulo Zoological Studies 63:46 (2024) doi:10.6620/ZS.2024.63-46 1 © 2024 Academia Sinica, Taiwan Ridge and Rio Grande Rise, focused in the investigation of deep-sea ecosystems associated with geological and tectonic features in the area (Hajdu et al. 2017; Kitazato et al. 2017). Echinostylinos Topsent, 1927 is a cold-water genus (55–2500 m), known from the North Atlantic, Northwest and South Pacific, with 11 species described this far. Included in the family Phellodermidae van Soest & Hajdu, 2002 with Phelloderma Ridley & Dendy, 1886, both genera are differentiated especially by the morphology of their isochelae. Affinities of phellodermids and cladorhizids (Abyssocladia Lévi, 1964 - Cladorhizidae Dendy, 1922, carnivorous sponges) are gradually becoming clearer. Originally proposed as pertaining to the Mycalidae Lundbeck, 1905 (Lévi, 1964), Abyssocladia has been placed amidst cladorhizids (Asbestopluma Topsent, 1901, Chondrocladia Thompson, 1873, Cladorhiza Sars, 1872) since its inception (Lévi 1964; Koltun 1970). Anyhow, van Soest and Hajdu (2002) considered Abyssocladia to be a likely junior synonym of Phelloderma, classified in their newly proposed Phellodermidae, that also included Echinostylinos. This decision was based on an interpretation of the chelae of these sponges to be of arcuate morphology, thus prompting recognition of their affinities to the abandoned suborder Myxillina (Morrow and Cardenas 2015). Subsequent work by Vacelet (2006) observed that sigmancistras were present in all seven species known until then, and some showed evidence of carnivory. This led him to transfer Abyssocladia to Cladorhizidae, despite a belief that the latter family might be polyphyletic. Molecular data generated by Vargas et al. (2012) verified the monophyly of Cladorhizidae, provided Abyssocladia was left in it. While Cladorhizidae includes 15 genera currently (de Voogd et al. 2022), Phellodermidae is left with Echinostylinos and Phelloderma, whose affinities have not yet been verified by any independent data source. Göcke et al. (2016) found additional evidence of “myxilline” affinity in their newly described Phelloderma oxychaetoides Göcke, Hajdu & Janussen, 2016, which possessed oxychaetes of similar morphology to those observed in irrefutable “myxillines” such as Chaetodoryx Topsent, 1927. It seems thus that Phelloderma and consequently Phellodermidae, are best classified away from the Cladorhizidae. For now, the “true” affinities of Echinostylinos remain an open question. As currently understood, Echinostylinos is recognizable by the possession of (strongylo) style megascleres and microscleres that include arcuate isochelae and, most of the times, sigmas. Notwithstanding, the first record for the South Atlantic was made only recently from 1100‒1130 m depth at Campos Basin – E. brasiliensis Carvalho et al. 2016. This species bears tetradentate unguiferate isochelae as its only microscleres. With the above in mind, the main objectives of the present study were to describe two new South Atlantic species of Echinostylinos (including its first abyssal record) and one of Chondrocladia. In addition, two species formerly assigned to Echinostylinos are reassessed here, briefly redescribed, and transferred to Abyssocladia. An identification key for all known species of the former genus is proposed with updated comparative table, and a few considerations on its biogeography are advanced. MATERIALS AND METHODS The specimens studied are part of the Museu Nacional/UFRJ Porifera collection and they were part of two different expeditions. In the first of these, in 1987, MD-55 expedition with the R/V ‘Marion Dufresne’, specimens were dredged on the VitoriaTrindade seamounts (SE Brazil). In the other, in 2013, the Iata-Piuna expedition with the ‘Shinkai’ manned submersible and “R/V “Yokosuka”, specimens were collected by robotic arms on the São Paulo Ridge and Rio Grande Rise (SW Atlantic international waters; see Fig. 1). Specimens were studied following the standard procedures outlined in Hajdu et al. (2011). Morphometric data was obtained from 30 spicules, unless stated otherwise. Scanning electron microscopy pictures were taken on a JEOL JSM-6390LV Scanning Electron Microscope (SEM) of the Museu Nacional. Additional comparative material of Echinostylinos species from other Porifera collections were analyzed (Muséum National d’Historie Naturalle). Abbreviations used: MNHN ‒ Porifera collection, Muséum National d'Histoire Naturelle; MNRJ ‒ Porifera Collection, Museu Nacional/UFRJ, Rio de Janeiro, Brazil. RESULTS TAXONOMY Phylum Porifera Grant, 1836 Class Demospongiae Sollas, 1885 Subclass Heteroscleromorpha Cárdenas, Pérez & Boury-Esnault, 2012 Order Poecilosclerida Topsent, 1928 Family Phellodermidae van Soest & Hajdu, 2002 Genus Echinostylinos Topsent, 1927 Diagnosis: Anastomosing branches, erect bushes or semiglobular masses. Surface irregular or conulose. Skeleton of smaller ectosomal megascleres page 2 of 19Zoological Studies 63:46 (2024) © 2024 Academia Sinica, Taiwan (styles or subtylostyles) or assuming a partly erect and partly tangential position and larger choanosomal styles forming an axially condensed mass or a vague reticulation of tracts and single spicules. Microscleres arcuate chelae and sigmas (modified from van Soest and Hajdu 2002). Remarks: Diagnosis adapted to included styles as the smaller ectosomal megascleres. Echinostylinos iatapiuna sp. nov. (Fig. 2) urn:lsid:zoobank.org:act:838127E5-28EA-4812-AC34F123F61D9A61 Material examined: Holotype. MNRJ 17631, São Paulo ridge, Southwest Atlantic (Iata‒Piúna Expedition, ‘Shinkai’ submersible, Dive 156–1, YK13-04, st.02, -28.4033 / -40.9816), coll. H. Kitazato, depth 2300– 3300 m, 29.IV.2013. Diagnosis: Echinostylinos iatapiuna sp. nov. is the only Echinostylinos with a single category of megascleres (styles) and one category each of sigmas and spatulate arcuate tridentate isochelae larger than 60 µm. Description: Cushion-shaped, roundish and flattened like a cookie, 30 × 2.7 mm in area, 7 mm thick. Compressible, with irregular surface, color beige in ethanol (Fig. 2A). Skeleton: Ectosome and choanosome undifferentiated. Spongin abundant. Megascleres in unito paucispicular, inter-crossing, loose ascending tracts, further obscured by megascleres strewn in confusion. Sigmas scattered everywhere, and isochelae mainly in the ectosome (Fig. 2B). Spicules: Megascleres a single category of styles (Fig. 2C), smooth, straight to slightly curved, tapering gradually to acerate ends, 1100–1219–1350 × 20–24.8– 28 µm. Microscleres isochelae and sigmas. Tridentate Fig. 1. Map of the sampled region in the Southwestern Atlantic: A) Sampling locality of Echinostylinos iatapiuna sp. nov.; B) Sampling locality of Echinostylinos abyssalis sp. nov.; and C) Sampling locality of Chondrocladia (Chondrocladia) trisigmata sp. nov. N page 3 of 19Zoological Studies 63:46 (2024) © 2024 Academia Sinica, Taiwan Fig. 2. Holotype of Echinostylinos iatapiuna sp. nov. (MNRJ 17631). A, preserved specimen; B, transversal section of skeleton; C, styles: D, isochelaes; E, sigmas. Scale bars: A = 5 mm; B‒C = 100 µm; D‒E = 10 µm. page 4 of 19Zoological Studies 63:46 (2024) © 2024 Academia Sinica, Taiwan isochelae (Fig. 2D), with short, feebly developed spatulate teeth, 68–73.5–88 µm. Sigmas, smooth (Fig. 2E), C or S‒shaped, tapering gradually to both, asymmetrical apices, 60–71.1–88 µm. Distribution and Ecology: Known only from its type locality, at bathyal depths (2300–3300 m) in the São Paulo ridge (SW Atlantic). The holotype was sampled associated to corals (Solenosmilia spp.). Etymology: The specific epithet, iatapiuna, is proposed as a noun in apposition, and refers to the name of the oceanographic expedition in which this new species was collected. Remarks: The species appearing closest to Echinostylinos iatapiuna sp. nov. is E. schmidtii (Arnesen, 1903; type locality Norway, 500 m depth), sharing the same spicule categories, viz. one category each of styles, isochelae and sigmas. However, the dimensions of these are considerably different so that no doubt rests that both are separate valid species. The type of E. schmidtii is apparently lost (cf. Carvalho et al. 2016), but the original description of isochelae around 40, and sigmas around 20 µm long, sets it confidently apart from the new species’ 67‒88 µm long isochelae, and 60‒88 µm long sigmas. Additional species in Echinostylinos differ even further, both in terms of spicule categories present, as well as on morphometric aspects (see Table 2: a new version here of Table 8 in Carvalho et al. 2016). Comparison to the second new species proposed in the present study will be carried in the remarks to E. abyssalis sp. nov. (see below). Echinostylinos abyssalis sp. nov. (Fig. 3) urn:lsid:zoobank.org:act:E21D5BEE-CA32-4F83-BBF9B09979F8D0ED Material examined: Holotype. MNRJ 17633, São Paulo Ridge, Southwest Atlantic (Iata‒Piúna Expedition, Shinkai submersible, Dive 1333, -28.5133 / -41.6533), coll. H. Kitazato, depth 4008 m, 23.IV.2013. Diagnosis: The only Echinostylinos with two categories of megascleres differentiated only by width, and microscleres, which are solely tridentate arcuate isochelae (tending to unguiferate morphology). Description: Erect, perhaps semi-infundibuliform (half a funnel; but in situ image not very sharp, and collected specimens fragmented), fragile, largest fragment 75 mm long × 8 mm wide at the base, and 28 mm wide on apical region (Fig. 3B); smallest fragment 60 mm long × 4 mm wide at the base, and 29 mm wide on the apex. Compressible with irregular surface, color whitish in situ, beige in ethanol (Fig. 3A). Skeleton: Ectosome with thinner megascleres (styles II) in ascending bundles. Choanosome with thicker megascleres (styles I) in ascending, loose, paucito multispicular tracts, sometimes forming ill-defined multispicular tracts. Microscleres abound all around (Fig. 3B). Spicules: Megascleres are two categories of styles, both smooth and slightly curved, tapering gradually to acerate ends. Styles I, 572–781.8–854 × 17–19.7–24 µm (Fig. 3C); styles II, 446–497–582 × 7–10.6–12 µm (Fig. 3D). Microscleres, tridentate arcuate isochelae with pointy teeth, 29–32.5–36 µm (Fig. 3E). Distribution and Ecology: Known only from its type locality, at an abyssal depth (4008 m) in the São Paulo ridge (SW Atlantic). Holotype founded growing on consolidated bottom. Etymology: The specific epithet, abyssalis, is proposed as a noun in apposition, and refers to the type specimen’s depth zone of occurrence, the abyssal zone. Remarks: Echinostylinos abyssalis sp. nov. is distinguished among its congeners as the sole species bearing two categories of styles (differentiated by width), and a single category of microscleres, namely tridentate, somewhat unguiferate, arcuate isochelae. When compared to other Echinostylinos spp., E. brasiliensis (also from the SW Atlantic) appears the closest. However, E. brasiliensis presents only one category of megascleres and also of isochelae. With isochelae even smaller (22–28 µm) than those in the new species (29–36 µm). When compared to the other new species described above, E. abyssalis sp. nov. presents two categories of megascleres and only one of isochelae, while E. iatapiuna sp. nov. presents only one category of megascleres and isochelae plus sigmas. Regarding the isochelae shapes, E. abyssalis sp. nov. presents somewhat unguiferate alae, while in E. iatapiuna sp. nov. is spatulate. Additional species of Echinostylinos differ in terms of spicule categories present, and on morphometric aspects. Family Cladorhizidae Dendy, 1922 Genus Chondrocladia Thomson, 1873 Diagnosis: Cladorhizidae with anchorate isochelae (Lee et al. 2012). Subgenus Chondrocladia (Chondrocladia) Thomson, 1873 Diagnosis: Chondrocladia without a layer of special spicules (spear-like tylostyles or trochirhabds), lacking special rostriform (snoutlike) subtylostyles in filaments or terminal balls, and without planar vanes formed of evenly spaced upright branches (Lee et al. 2012). page 5 of 19Zoological Studies 63:46 (2024) © 2024 Academia Sinica, Taiwan Fig. 3. Holotype of Echinostylinos abyssalis sp. nov. (MNRJ 17633). A, specimen in situ; B, specimen in ethanol; C, styles I; D, styles II; E, transversal section of skeleton; F, isochelae. Scale bars: B = 10 mm; C, D = 100 µm; E = 500 µm; F = 5 µm. page 6 of 19Zoological Studies 63:46 (2024) © 2024 Academia Sinica, Taiwan Chondrocladia (Chondrocladia) trisigmata sp. nov. (Fig. 4) urn:lsid:zoobank.org:act:ABEFBD2A-55AC-4051-B5FE50E7FA873FFF Material examined: Holotype. MNRJ 16000, continental rise to the south of the Vitória-Trindade seamounts’ chain, off SE Brazil, Southwest Atlantic (R/ V ‘Marion Dufresne’ MD-55 Expedition, Stn. 8 CP17, -21.134 / -38.4349), collection method: dredge, 3250– 3270 m depth, coll. N. Boury-Esnault, 11.V.1987. Diagnosis: The only Chondrocladia (Chondrocladia) species with three categories of sigmas. Description: Massive, rounded; smooth surface with scattered circular structures. No projections seen. Specimen in fragments (Fig. 4A), the biggest one 12 × 12 mm in area and 5 mm thick. Compressible consistence, rough and easy to tear. Color beige in ethanol. Skeleton: Ectosomal skeleton with a layer of organic material, megascleres type II and microscleres arranged irregularly. Choanosomal skeleton with an irregular reticulation of megascleres just below the ectosome, and ascending tracts of styles I with microscleres randomly scattered in the body fragment analyzed. Spicules: Megascleres are two size categories of styles. Styles I (Fig. 4C), smooth, fusiform, one end rounded and the other tapering gradually, conical or hastate; 1287–2126.9–3318 × 19–32.8–50 µm. Styles II (Fig. 4D), smooth, straight with one end rounded and the other hastate to conical; 378–1000.7–1232 × 14–18.6–22 µm. Microscleres are two categories of anchorate isochelae, and three categories of sigmas. Isochelae I (Fig. 4E), smooth, long shafted, tridentate with pointy alae, 65–82.2–98 µm long. Isochelae II (Fig. 4F), smooth tridentate with pointy alae, 37–42–50 µm long. Sigmas I (Fig. 4G), slender, tapering gradually to sharp ends, 77–90.5–96 µm long. Sigmas II (Fig. 4H), similar to sigmas I, but shorter, 22–28.2–36 µm long. Sigmas III (Fig. 4I), C-shaped, markedly fusiform, with central part bearing lateral fimbria-like expansions, 9.6–10.8–13 µm long. Distribution and Ecology: Known only from its type locality, the continental rise to the south of the Vitória-Trindade seamounts chain region (SW Atlantic), at 3250–3270 m depth. Etymology: The specific epithet, trisigmata, is used as a noun in apposition, and refers to the three categories of sigmas present in the new species, a distinguishing feature within its subgenus. Remarks: Although these fragments, at first look, do not look like a carnivorous sponge, the specimen was dredged in 1984 on board of the R/ V ‘Marion Dufresne’, it is very common to receive damaged specimens or even only fragments. After careful analyzes of its peculiarities on the surface, plus skeleton and spicule set, we were convinced of its classification. Chondrocladia (Chondrocladia) presents 34 valid species distributed worldwide (Ekins et al. 2020; de Voogd et al. 2022). The new species differs from its congeners by the presence of three categories of sigmas (see comparative table including data from all species from every other subgenus, table 10 in Ekins et al. 2020). Chodrocladia (C.) antarctica Hentschel, 1914 and C. (C.) concrescens (Schmidt, 1880) (sensu Hestetun et al. 2016b) were originally reported with two categories each of styles, isochelae and sigmas, however, both species do not present a third category of sigmas (similar to the sigmoid isochelae of Monanchora arbuscula), an apomorphy of the new species. Further distinctness is apparent from a detailed analysis of spicules’ shape and micrometries. Both formerly known species have sigmas that can reach considerably larger dimensions (143–165 µm, and 69–97 µm, respectively; cf. Göcke and Janussen 2013; Topsent 1920). In the case of C. (C.) concrescens, isochelae I can also be much larger (110–130 µm) and have six teeth, while isochelae II differ markedly in their bird-cage shape plus four to six teeth (Topsent 1920, fig. 3b; Hestetun et al. 2016b, fig. 7D). New taxonomic combinations In order to clarify some questions pointed in other studies related to Echinostylinos species (e.g., see Carvalho et al. 2016; Vacelet and Kelly 2022), taxonomic revisions are needed and two new combinations are proposed below: Genus Echinostylinos Topsent, 1927 Echinostylinos lingua new comb. (Koltun, 1970) Mycalopsis lingua Koltun, 1970: 207; Fig. 21; Plate VIII, 3. Type Material: Holotype, ZIRAS 16399, Zoological Institute of the Russian Academy of Sciences, Northwestern Pacific, Kurile-Kamchatka Trench area, off Shikotan Island (Station 5641, R/V “Vityaz”), 472–479 m depth (not studied here). Diagnosis: Species characterized by the presence of only one category of megascleres (styles) 550–870 × 13–16 µm. Microscleres are palmate isochelae in two categories, and sigmas. Isochelae I with 44–55 µm and II with 18–32 µm. Sigmas, 77–148 µm (Koltun, 1970). Remarks: Carvalho et al. (2016) considered the species Esperiopsis lingua (Koltun, 1970) as an page 7 of 19Zoological Studies 63:46 (2024) © 2024 Academia Sinica, Taiwan Fig. 4. Holotype of Chondrocladia (Chondrocladia) trisigmata sp. nov. (MNRJ 16000). A, preserved specimen (fragments); B, transversal section of skeleton; C, styles I: D, styles II; E, six isochelae I and one isochela II facing one of them; F, isochelae II; G, sigmas I; H, sigma II; I, sigmas III. Scale bars: A, H = 5 mm; B, D = 100 µm; C = 500 µm; E, G = 10 µm; F, I = 2 µm. page 8 of 19Zoological Studies 63:46 (2024) © 2024 Academia Sinica, Taiwan Echinostylinos species in their comparative table, although they did not formally propose the new combination, which is done here. Genus Abyssocladia Lévi, 1964 Diagnosis: Cladorhizidae most often pedunculate, carrying a disk-shaped or flabelliform body with a radial architecture, in other cases pinnate or branching. Microscleres are a combination of abyssochelae, cleistochelae, arcuate chelae and/or sigmancistras, but not placochelae (Hestetun et al. 2016). Abyssocladia glomeris new comb. (Topsent, 1904) (Fig. 5) Esperiopsis glomeris Topsent, 1904: 213, pl. XVII, fig. 3. Camptisocale glomeris (Topsent, 1904). Topsent (1927: 7). Material examined: Schizotype (slides presently re-examined). MNHN DT 1000, off Terceira, Azores, NE Atlantic (stn 866, S.A.S. Le Prince de Monaco; 38.8806 / -27.3847), 599 m depth, coll. S.A.S. Le Prince de Monaco, R/V ‘Princesse Alice’,02.VIII.1897. Diagnosis: The only species of Abyssocladia with two categories of styles, 1400–1500 × 17–20 µm and 900–1000 × 7–8 µm, and only arcuate isochelae as microscleres (46–60 µm), often of abyssochelae morphology. Brief Redescription (adapted from Topsent, 1904): The specimen is a whitish, elongated fragment, 20 mm long × 4 mm thick, without support; with soft consistency, smooth surface, and without distinct openings. The schizotype consists of a couple of slides with spicule dissociations and skeletal fragments. Skeleton: Ectosome with tangential and compact bundles of styles II. Choanosome with styles I forming multispicular tracts. Microscleres abundant and randomly distributed (Fig. 5A; modified of Topsent 1904). Spicules: Megascleres, styles in two categories. Styles I (Fig. 5A), smooth and straight sometimes slightly curved. Styles II (Fig. 5B), smooth and straight. According to Topsent (1904): styles I: 1400–1500 × 17–20 µm; styles II: 900–1000 × 7–8 µm. Microscleres, arcuate isochelae (Fig. 5C, D) with alae of both extremities ranging from totally separated to strongly interwoven as in abyssochelae: 46–60 µm (measures confirmed by the authors). Distribution: Known only from its type locality, NE Atlantic, Azores, 599 m depth (Topsent, 1904). Remarks: We propose the transfer of Echinostylinos glomeris (Topsent, 1904) to Abyssocladia Lévi, 1964 on account of its habit, skeleton and spicules, which appear more related to the latter genus, than to Echinostylinos or Phelloderma. The species originally described as Esperiopsis glomeris was transferred to Echinostylinos by van Soest and Hajdu (2002). Their rationale for the transfer actually supports our proposition, since they highlighted the skeletal similarity to Echinostylinos, but recognized the morphology of the isochelae in glomeris seemed to contradict this view, an observation they underestimated as likely of specific value only. Isochelae alone do not allow recognition of Abyssocladia spp. in many cases, but the typical branching shape and habit encourage us to transfer Esperiopsis glomeris to Abyssocladia. On other Echinostylinos During the process of review of the genus to describe the new species, considerations were taken regarding some known species of Echinostylinos: Carvalho et al. (2016) discussed the possibility of a E. shimushirensis and E. tubiformis be synonymous. Here, we tabulated their morphological characteristics and habitat information based on their descriptions available (Fig. 6; Table 1). Previous studies had discussed about spicule shape and classification of Echinostylinos species (Carvalho et al. 2016; Vacelet and Kelly 2022), we re-analyzed the type material of Echinostylinos gorgonopsis, here redescribed below: Echinostylinos gorgonopsis Lévi, 1993 (Fig. 7) Abyssocladia mucronata Vacelet, 2020: 269; Figs. 7–8. Material examined: Holotype. Echinostylinos gorgonopsis Lévi, 1993 MNHN DCL 3612, New Caledonia, SW Pacific (BIOCAL 74; st. CP 45, ‘l'ORSTOM’ campaign; -23.1717 / 167.7163), 950– 1000 m depth, coll. R/V 'Jean Charcot'. Diagnosis: The only species of Abyssocladia with anisoxeas (525–650 × 4–5 µm) and tornotes (250–370 × 4–5 µm) as megascleres, and abyssochelae as its sole microscleres (30–50 µm). Brief redescription (based on the holotype and Lévi (1993) description): Sponge, erect, arborescent, 14 cm long × 12 cm wide, with a short and cylindrical stalk (ca. 2 cm, broken). Most branches at the same plane, with 3–7 successive dichotomies. Irregular surface, rough to the touch, with small projections (lobes), giving the impression of a slight annealing, and with numerous circular openings at the apical branches. Sponge yellow to ocre in ethanol (modified from Lévi page 9 of 19Zoological Studies 63:46 (2024) © 2024 Academia Sinica, Taiwan is impressive how much the morphology of the chela varies among species attributed to Echinostylinos, even after the above genus transfers argued for. Two obvious groups appear recognizable. Species with markedly curved, slender, unguiferate chelae with quite small heads include E. brasiliensis and E. mycaloides. Species with markedly curved, stout, seemingly spatulate chelae with small, compressed heads, include E. lingua new comb., E. reticulatus (type species), E. shimushirensis, E. stylophora and E. tubiformis. Standard tridentate spatuliferous chelae might suggest evolutionary proximity between E. iatapiuna sp. nov. and E. patriciae, but the chelae of the later need a more detailed study of their micromorphology under SEM before further inference of its affinities can be built. Echinostylinos hirsutus (reduced sigmoidchelae), and E. abyssalis sp. nov. (tridentate arcuate chelae with pointy alae) do not seem to belong in any obvious similarity cluster of isochelae morphology in this genus. The chelae of E. schmidti are too roughly drawn to allow any inference of affinities, and its type specimen appears to be lost, thus preventing any further conclusions (H.T. Rapp, in litt.; cf. Carvalho et al. 2016). The possibility that E. shimushirensis and E. tubiformis might be synonymous was already commented by Carvalho et al. (2016). We prefer to keep both separate and valid on account of a series of characters, reinforced by their known occurrences 7600 km apart from each other. The habits and the morphology of the sigmas as well, differ between both species (Fig. 6; Table 1). Echinostylinos shimushirensis (holotype, ZIRAS 10693) has a massive body, narrowed basally, with low conules abundantly spread at the surface; and a smaller category of u-shaped sigmas approaching the flagellate condition. Echinostylinos tubiformis (holotype, MNHN DCL 3611), on the other hand, is an erect sponge, gradually widening away from the base, and its sigmas are morphologically different from E. shimushirensis’ smaller category, which is c-shaped. Biogeographic considerations Only one Echinostylinos had been recorded from the South Atlantic until now, E. brasiliensis Carvalho, Lopes, Cosme & Hajdu, 2016. This number has raised to three after the proposition of two new species in the present study. The new species described above include samples with depth records between 2000 and 4008 meters deep in the Southwestern Atlantic. Most species of Echinostylinos were recorded from the bathyal zone, with the exception of E. patriciae, that is from the mesophotic (55–110 m) and E. abyssalis sp. nov., from the abyssal (4008 m). Surprisingly, species richness is a little higher in the Atlantic (seven spp) than the Pacific (five spp). No species has been recorded from the Indian Ocean yet. Latitudinally, there are two Boreal and ten Temperate species. Among the later, three are Subtropical. In terms of bathymetry, the Pacific holds the shallowest record (55 m, E. patriciae), while the Atlantic holds the deepest (4008 m, E. abyssalis sp. nov.). The deepest Pacific record is that of E. mycaloides (2265 m). The shallowest Atlantic record is that of E. schmidti (500 m). The new records proposed here contemplate the South Atlantic lower bathyal province (Watling et al. 2013), Chondrocladia (C) trisigmata sp. nov. and E. iatapiuna sp. nov.; and the Brazilian abyssal province, E. abyssalis sp. nov. The entire South Atlantic comprises only seven records to depths deeper than 4000 m. Among those, two are glass-sponges (Euplectella sanctipauli Castello-Branco, Collins & Hajdu, 2020 and Holascus stellatus Schulze, 1887) and five are demosponges (Cladorhiza inversa Ridley & Dendy, 1886, Chondrocladia (C.) levii Cristobo, Urgorri & Rios, 2005, Chondrocladia (C.) nicolae Cristobo, Urgorri & Rios, 2005, Chondrocladia (C.) vaceleti Cristobo, Urgorri & Rios, 2005, and E. abyssalis n. sp.). Concerning the last group, four of them were sampled in only one expedition in the Southeastern Atlantic (all belong in Cladorhizidae). This reflects how premature it is to advance any reasonable estimate of sponge diversity in South Atlantic’s bathyal and abyssal zones. Records are simply too sparse to allow any meaningful inference of species accumulation curves. CONCLUSIONS The present study adds two new species to Echinostylinos, transfers a species of Esperiopsis into this latter genus, but also proposes the transfer of one species formerly classified in Echinostylinos, to Abyssocladia, thus increasing the number of known species in Echinostylinos from 11 to 13 valid species and from 38 to 39 species in Abyssocladia. Additionally, a new species of Chondroncladia (Chondrocladia) is described here, increasing the number of known species in the subgenus from 34 to 35. The genus Echinostylinos was formerly known from a depth range of 55–2500 m (Carvalho et al. 2016), but both new species described here came from deeper zones, with E. abyssalis sp. nov. pushing the genus’ known deepest record into the abyssal, at 4008 m depth. As highlighted above, the genus demands an integrative taxonomic revision in order to verify its monophyly, which is challenged among other aspects, page 16 of 19Zoological Studies 63:46 (2024) © 2024 Academia Sinica, Taiwan by the marked disparity of isochelae morphologies seen in its species. Furthermore, given the finding of the new species reported above, their relative aggregation in the SW Atlantic, and the incompleteness of the inventory of South Atlantic’s deep-sea biota as a whole, it is to be expected that new species will come up with continued exploratory investigations in this area. The recent finding of an hexactinellid sponge garden in the Rio Grande rise (Hajdu et al. 2017) is a strong support for this claim. If an entire habitat can hide shallower than 1000 m depth, tiny little creatures deeper than 3000– 4000 m can surely do it much better. Acknowledgments: The authours are deeply thankful to CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior), CNPQ (Conselho Nacional de Desenvolvimento Científico e Tecnológico), FAPERJ (Carlos Chagas Filho Rio de Janeiro Research Support Foundation) and Smithsonian Institution, Peter Buck Fellowship Program for the provision of grants and/ or fellowships. The authors are grateful to Dr. Jose Angel Alvarez Perez, Dr. Paulo Sumida, Dr. Hiroshi Kitasato and the whole staff of the R/V ‘Yokosuka’ and ‘Shinkai’ for all the specimens supplied (Iata Piúna expedition), Dr. Nicole Boury-Esnault for allowing the repatriation of the collection gathered off SE Brazil in 1987 during the MD55 R/V ‘Marion Dufresne” expedition, Dr. Isabelle Domart-Coulon for her kind reception and granting the access of CCB to the MNHN Porifera collection, and Dr. Alexander Ereskovsky who cordially analyzed and supplied some fragments of E. shimushirensis from Koltun’s collection located at the Zoological Institute of the Russian Academy of Sciences (St. Petersburg, Russia). Authors are thankful also to Camila Messias and Beatriz C.A. Cordeiro for SEM operation at the former Center for Scanning Electron Microscopy of Museu Nacional/UFRJ. Authors’ contributions: CCB performed the species description, discussion and draft the manuscript. 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