Hamacantha (Vomerula) novacula Ekins & Baker & Hooper 2023, sp. nov.
Creators: name: Ekins, Merrick
name: Baker, Soraya
name: Hooper, John N. A.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Demospongiae
Merliida
Hamacanthidae
Hamacantha
Hamacantha novacula

description: Hamacantha (Vomerula) novacula sp. nov. Ekins & Hooper
Figures 1, 3, Tables 1, 2
urn:lsid:zoobank.org:act: 49DB7D5B-D49D-4494-B476-65B74F0ABFFD
Material examined: Holotype, QM G337915, Seamount, ridge near summit of South Recorder Guyot Seamount, Queensland, Australia, -25.13, 154.9983, 880–1100 m, Rock dredge, TMD-22MNF-SS 2012-V07, Coll. Greg Webb on RV Southern Surveyor, 8/XII/2012. Paratype, QM G326453, Cascade Seamount, Tasmania, Australia, -43.8613, 150.4286, 800–1000 m, SS 0207-066-029, Coll. A. Williams and M. Schlacher on RV Southern Surveyor, SS 02/ 2007, 9/IV/2007. Paratype, QM G324761, Andy’s Hill, Tasmania, Australia, -44.175, 146.98833, 881–1154 m, Sled— Benthic, Solenosmilia habitat, SS 01/97, Coll. T. Koslov, on RV Southern Surveyor, 29/I/1997.
Etymology: L. novacula, f. shaving knife, in reference to the extra sharp fimbriae of the large diancistras.
Description: The holotype is a fragile, lace-like, encrusting sponge, attached to a rock (Fig. 3A). It was originally 45 mm long, 25 mm wide and 2 mm in height. It has a smooth velvety surface, with no remaining obvious oscules. The aquiferous are clearly visible through the transparent ectosome. The prevalent circular ostia form rows on the surface (Figs. 3A,B). They are 0.3 mm in diameter, often with protective sharp tips from the styles and (Fig. 3 B, C). The areas between the ostia are visible as semitransparent lines where the spicules are not clustered, giving the appearance of a suburban street network (Fig. 3A). The sponge is white and translucent on deck and after preservation. The paratype QM G326453 is also growing on a rock, but paratype QM G324761 is growing on on Solenosmilia variabilis.
Skeleton: The ectosomal skeleton is composed of tangential styles, arranged in a multispicular reticulated pattern around the circular ostia. The supportive styles from the choanosome pass through the ectosomal layer to provide a protective perimeter around the ostia. The small diancistras (II) sometimes occur in the very thin (2 µm) ectosomal layer, where the randomly sparsely scattered styles occur between the ostia. The choanosomal skeleton consists of bundles of ascending twisting columns of styles supporting the ectosomal layer and penetrating through the ectosome to produce the hispid surface (Fig. 3C). Both diancistras occur in these waisted twisted columns (Fig. 3C).
Spicules: The megascleres are styles, which are abundant, fusiform, straight, sharply pointed, and thickest in the centre (Fig. 3I). The blunt end is much narrower than the middle and has a rounded style end (see Table 1 for measurements). The large diancistras (I) are common, twisted at about 70 o, the thin sharp fimbriae are very short on the inner shaft on a raised support. The fimbriae on the corresponding face of the hook is easily twice as long. Both faces have such an obvious sharp blade, with the appearance of a razor blade inserted into a razor blade holder (Fig. 3D). The smaller diancistras (II) are also common, they have sharp opposing alae with a reverse barb, thus resembling a fishhook (Fig 3F). An example of the reverse barb missing on some of the smaller diacistras was found on one of the specimens (QM G326453) (Fig. 3H). Rare examples were found of ‘teeth’ on the smaller diancistras on one of the specimens (QM G324761) (Fig. 3G). The small diancistras only have a small shaft twist of approximately 15 o (Fig. 3F). The sigmas are rare, thin and have a similar C shape to the small diancistras (Fig. 3E). One of the paratypes (QM G324761) also had tylostyles and subtylostyles, but these could not be found in the section and are considered non-native.
Remarks: The new species H. (V.) novacula sp. nov. is very similar to the closely related species of H. (V.) acerata and H. (V.) umisachii. It differs from these two species most obviously be the shape of the large diancistras. This is also the main difference between H. (V.) acerata and H. (V.) umisachii. The shape and arrangement of the fimbriae is unique for the different species and consistent within the new species. The smaller diancistras (II) of the new species are similar in shape and the presence of a reverse barb is also similar to those of H. (V.) acerata and H. (V.) umisachii. The diancistras (II) of the new species are generally larger and lack the additional formations around the centre of the diancistras that usually occur in H. (V.) acerata (Fig. 2C). The sigmas are larger in the new species and in H. (V.) umisachii compared to H. (V.) acerata. The styles in the new species are longer and more tapering at the tyle end than those of H. (V.) umisachii and H. (V.) acerata.
description: Published as part of Ekins, Merrick, Baker, Soraya & Hooper, John N. A., 2023, First records of Hamacantha species from seamounts off eastern Australia (Porifera, Demospongiae, Merliida), with description of four new species, pp. 382-400 in Zootaxa 5318 (3) on pages 385-388, DOI: 10.11646/zootaxa.5318.3.4, http://zenodo.org/record/8166946