Hamacantha (Vomerula) jeanvaceleti Castello-Branco & Hajdu 2018, sp. nov.
Creators: name: Castello-Branco, Cristiana
name: Hajdu, Eduardo
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Demospongiae
Poecilosclerida
Hamacanthidae
Hamacantha
Hamacantha jeanvaceleti

description: Hamacantha (Vomerula) jeanvaceleti sp. nov.
Fig. 2
Holotype. MNRJ 21424, Rio Grande Rise, SW Atlantic (PROERG, ERG 17-L2; - 31.5656 S / - 34.2850 W), about 2200‒1600; coll. R.V. ‘ Marion Dufresne’, 2011.07.0 8.
Paratypes. MNRJ 21423, 21425, Rio Grande Rise, SW Atlantic (PROERG, ERG 61‒L2, ‒ 33.5747 S / ‒ 31.0970 W), 1245‒ 1165 m depth, coll. R.V. ‘ Marion Dufresne’, 2011.07.15.
Comparative Material. Hamacantha (Vomerula) atoxa Lévi, 1993 — MNHN DCL 3595 (Holotype), BIOCAL 48 (‒ 20.5108 S / 166.8383 E, New Caledonia), 440 m depth.
Hamacantha (Vomerula) forcipulata Lévi, 1993 — MNHN DCL 3596 (Holotype), BIOCAL 128 (‒ 20.51667 S / 166.84167 E, New Caledonia), 440‒460 m depth.
Hamacantha (Vomerula) integra Topsent, 1904 — MNHN DT 1068 (Holotype), Yacht ‘Princesse Alice’ stn. 587 (38°36'40" N / ‒ 27°17'15"W, Azores), 793 m depth, coll. Albert I Prince of Monaco, 19.VII.1895 (begin date).
Diagnosis. This is the only species of Hamacantha (Vomerula) with styles and two categories of diancistras, the smaller ones cyrtancistra-like.
Description. Specimens thin and delicate, encrusting, holotype 12.5 x 6 mm in area, and 1‒4 mm thick (Fig. 2A). Surface smooth, slightly velvety to the touch, oscula not visible. Consistency very soft and fragile. Colour alive not recorded, transparent to off white in ethanol.
Skeleton. Ectosomal skeleton a loose tangential reticulation of styles. Choanosome cavernous, with abundant tracts of megascleres whose endings support the ectosome (Fig. 2B).
Spicules (Table 1). Megascleres styles (Fig. 2C), fusiform, straight to slightly curved, tapering gradually, 398‒453.5‒524 x 10 ‒10.8‒12 µm. Microscleres: diancistras in two categories. Diancistras I (Fig. 2D), straight to contorted, fimbriae and notches not well marked, hooks each about 1/4 the total length, 194‒235.9‒281 µm long. Diancistras II, cyrtancistra-like in shape, (Fig. 2E) stouter, smooth, with hooks well marked, 29‒48‒62 µm long.
Distribution and ecology. Known only from its type locality, the Rio Grande Rise (SW Atlantic), between 1165 and 2200 m depth.
Etymology. The species is named in honour of Dr Jean Vacelet, whom, among many other endeavours, markedly contributed to our knowledge of cave, as well as deep-sea sponge biodiversity.
Remarks. Subgenus Hamacantha (Vomerula) includes 18 valid species worldwide (Table 2). Most of them (11) are recorded from the Atlantic/Mediterranean: H. (V.) agassizi Topsent, 1920, H. (V.) azorica Topsent, 1904, H. (V.) bowerbanki Lundbeck, 1902, H. (V.) carteri Topsent, 1904, H. (V.) esperioides (Ridley & Dendy, 1886), H. (V.) falcula (Bowerbank, 1874), H. (V.) integra Topsent, 1904, H. (V.) megancistra Pulitzer-Finali, 1978, H. (V.) microxifera Lopes & Hajdu, 2004, H. (V.) tenda (Schmidt, 1880), and H. (V.) tibicen (Schmidt, 1880). The latter was deemed unrecognizable by van Soest (1984). Among all Atlantic species of Hamacantha (Vomerula), the new species is most similar to H. (V.) carteri and H. (V.) esperioides. Hamacantha (V.) jeanvaceleti sp. nov. is closer to them because they share two categories of diancistras. But both species present styles bigger than in H. (V.) jeanvaceleti sp. nov., aside sigmas, which are absent in the new species. Another important point of distinction is the morphology of the second category of diancistras, as none of these species possess nearly perfectly c-shaped diancistras as the new species does. The latter are remindful of the cyrtancistras of Pozziella Topsent, 1896, differing only in their much smaller size in comparison to those present in Pozziela, which made us decide to name them as diancistras. The only species with diancistras of similar morphology are H. (V.) acerata Lévi, 1993 (New Caledonia) and H. (Zygherpe) desmacelloides Hajdu et al. 2015 (Peru). The former species presents diancistras and sigmas, the smaller diancistras (termed sigmancistras by Lévi, 1993) somewhat similar to the smaller diancistras in the new species, for their deep curve, pronounced hooks, but variously marked notches, from obvious to indistinct. Hamacantha (Z.) desmacelloides differs in many aspects from the new species, partly reflected in its classification in another subgenus. As regards its diancistras, the same ‘pronounced hook—indistinct notch’ aspect is present, albeit in much larger diancistras (148‒217 µm), which, on top of this, are only shallow-curved, organized in rosettes, and likely not homologous to the smaller diancistras in the new species.
description: Published as part of Castello-Branco, Cristiana & Hajdu, Eduardo, 2018, Two new Hamacantha (Vomerula) from the Rio Grande Rise (SW Atlantic) (Hamacanthidae, Porifera), pp. 69-77 in Zootaxa 4466 (1) on pages 70-72, DOI: 10.11646/zootaxa.4466.1.8, http://zenodo.org/record/1442116