Euplectella sanctipauli Castello-Branco &amp; Collins &amp; Hajdu 2020, sp. nov.
Creators: name: Castello-Branco, Cristiana
name: Collins, Allen G.
name: Hajdu, Eduardo
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Hexactinellida
Lyssacinosida
Euplectellidae
Euplectella
Euplectella sanctipauli

description: <i>Euplectella sanctipauli</i> sp. nov. (Figs. 4 and 5) Type Material Holotype. MNRJ 17630, São Paulo Ridge, Southwest Atlantic (‘Shinkai’ submersible Dive 1337—sample 5(1), Iata Piúna Expedition, 28 24 <i>′</i> 11.88 <i>″</i> S / 40 58 <i>′</i> 53.76 <i>″</i> W), 4,061 m depth, coll. E.P. Frazão, 29.IV.2013 LSID: urn:lsid:zoobank.org:act:8688B44F-7CAC-4A5B-8EBE-07400366CA9C Diagnosis Only known <i>Euplectella</i> without sieve-plate. Principal skeleton composed by long, smooth stauractins, choanosomal hexactins and pentactins, dermalia/atrialia as hexactins with reduced sword-shaped distal ray with low proclined scales, or reduced as a tubercle (pentactins). Basalia as anchorate spicules with spined shaft and eight teeth on the head. Microscleres: <b>fl</b> oricomes, graphiocomes and hemioxyhexasters. EXTERNAL MORPHOLOGY. The sponge consists of a delicate, thin-walled tube (Fig. 4) bearing a conspicuous surface reticulation, with dispersed oscula up to 4 mm in diameter, and basalia in a single tuft. Holotype (only specimen available), 137 mm long (including 34 mm long basalia/prostalia), 32 mm in maximum diameter. SKELETON AND SPICULES (Figs. 4 and 5). Principalia mostly stauractins with rays 2.4–5.9 mm long, 12–17 µm in diameter (<i>n</i> = 4), and elongated or rounded ends. Choanosomal spicules long, smooth hexactins (1.1–5.1 mm long rays (<i>n</i> = 10), elongated or rounded ends) and pentactins (3.8 – 7.6 mm long rays (<i>n</i> = 5), rounded ends). Dermalia and atrialia hexactins with a reduced and sword-shaped distal ray with low proclined scales (0.2–0.3 mm long), and tangential rays with elongated and rounded ends (0.3–0.4 mm long); pentactins with distal ray reduced as a tubercle, and smooth tangential rays (1.9–2.1 mm long; <i>n</i> = 2). Basalia composed of anchorate spicules with spiny shafts, and anchors with eight teeth. The largest spicule (broken) was 8.5 mm long. Microscleres are <b>fl</b> oricomes, graphiocomes and hemioxyhexasters. Floricomes with spined rays, and eight teeth on secondary rays, this last in number of 10–12 in each primary ray; diameter 110–130 µm, primary rosette 10–17 µm diameter. Graphiocomes observed with secondary rays always broken (68–85 µm long), primary rosette 10–14 µm diameter. Hemioxyhexasters (95–118 µm in diameter, <i>n</i> = 4) with two or three unbranched rays (45–50 µm in diameter); branched rays divide 7–10 µm from the origin and have secondary rays of length 10–20 µm (<i>n</i> = 4). (Fig. 5F). DISTRIBUTION AND ECOLOGY. Known only from its type locality, São Paulo Ridge (Southwest Atlantic; 4,061 m depth). The single specimen was collected from soft sediment, apparently the sole megafauna in several meters of terrain, and seemingly devoid of any macro-epibionts. ETYMOLOGY. The speci <b>fi</b> c epithet is used as a noun in apposition, derived from the species having been found at the São Paulo Ridge (deep SW Atlantic). Remarks <i>Euplectella</i> comprises 18 species around the world (<i>Reiswig &amp; Kelly, 2018</i>), classi <b>fi</b> ed by <i>Tabachnick &amp; Collins (2008)</i> into four main groups recognizable on the basis of the architecture of their principal skeleton: (1) mainly stauractins, (2) mainly hexactins with a reduced proximal ray and some stauractins, (3) pentactins and some hexactins and (4) stauractins, hexactins, hexactins with reduced proximal ray, hexactins with two reduced rays, tauactins and diactins. <i>Euplectella sanctipauli</i> sp. nov. should be included in the <b>fi</b> rst group, in addition to <i>E. aspergillum</i> Owen (1841), <i>E. curvistellata</i> Ijima (1901), <i>E. gibbsa</i> Tabachnick &amp; Collins (2008), <i>E. marshalli</i> Ijima (1895), <i>E. oweni</i> Herklots &amp; Marshall (1868), <i>E. paratetractina</i> Tabachnick, Janussen &amp; Menschenina (2008) and <i>E. simplex</i> Schulze (1896). The present species appears most similar to <i>E. aspergillum</i>, <i>E. gibbsa</i> and <i>E. simplex</i>, but differs from all of them by its possession of anchorate basalia with eight teeth, choanosomal hexactins and pentactins, and dermalia and atrialia including hexactins with a reduced and sword-shaped distal ray, as well as additional pentactins with distal ray reduced as a tubercle. In addition, <i>E. aspergillum</i> differs in having anchorate basalia with six teeth, and diactins; <i>E. gibbsa</i> differs in having anchorate basalia with four teeth, choanosomal tauactins and diactins; and <i>E. simplex</i> differs by its triactins and diactins. To date, this is the only <i>Euplectella</i> species without a sieve-plate, which clearly establishes <i>E</i>. <i>sanctipauli</i> sp. nov. as a new species.
description: Published as part of <i>Castello-Branco, Cristiana, Collins, Allen G. &amp; Hajdu, Eduardo, 2020, A collection of hexactinellids (Porifera) from the deep South Atlantic and North Pacific: new genus, new species and new records, pp. e 9431 in PeerJ 8</i> on pages 7-10, DOI: 10.7717/peerj.9431, http://zenodo.org/record/4624210
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