Hamacantha (Vomerula) levii, Ekins & Baker & Hooper, 2023

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, Zootaxa 5318 (3), pp. 382-400 : 395-397

Hamacantha (Vomerula) levii sp. nov. Ekins & Hooper

Figs 1 , 6 , Table 2

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Material examined: Holotype: QM G339187, Mellish Seamount, Coral Sea, Queensland, Australia, -17.4895, 155.88233, 983 m, Rock dredge, Keratoisis habitat, Station 14, IN2019_ V 04, iv50, Coll. J. Horowitz on RV Investigator , 14/VIII/2019.

Etymology: Named for Claude L é vi, who described many deep-water sponge species from the South Pacific.

Description: The holotype is a round, thin specimen 12 mm in diameter at its widest ( Fig. 6 A, B ). It is only 1 mm in height and encrusting on the base of the stem of a dead Keratoisis sp. It has a rough surface due to the protruding tangential styles. The preserved sponge has folds on the upper surface ( Fig. 6B ), most likely as the sponge was of a greater height underwater (possibly 2–4 mm in height) that collapsed once out of the water. The sponge has no apparent oscula, although it is possible there were oscules terminal in what could be conules of several millimetres in height, but these may have been destroyed in collection by the rock dredge. As is usual with this genus there are numerous scattered ostia 0.5 mm in diameter, that are obvious on the surface ( Fig. 6C ). The sponge is white on deck and in preservative, although highly translucent when preserved in ethanol.

Skeleton: The ectosomal skeleton consists of a tangential layer of styles, often surrounding the apparently randomly scattered ostia of 0.3–0.5 mm in diameter ( Fig. 6D ). The choanosomal skeleton was not obvious but consisted of the usual supporting bundles of styles typical for this genus

Spicules: The megascleres are styles, which are abundant, fusiform, straight, sharply pointed and thickest in the centre ( Fig. 6H, I ). The blunt end is much narrower than the middle and has a rounded style end. They measure 337–(410)–574 x 6.7–(10.4)–14.7 μm, n=29. The large diancistras (I) are not common, with the shaft twisted less than 45 o, the thin sharp fimbriae run the entire length of the inner surface except around the notch ( Fig. 6E ). These measure 102–(108)–119 x 5.9–(8.3)–10.5 μm, n=12. The medium sized elongated diancistras (II) are common, with the shaft twisted greater than 90 o, and have large equal, almost touching elongated fimbriae ( Fig. 6F ). These are less than half the size of the diancistras (I), and measure 28.8–(46.6)–66.1 x 1.2–(2.1)–3.1 μm, n=42. The small diancistras (III) are not common, with the shaft twisted greater than 90 o ( Fig. 6G ). These have large equal alae with almost touching curvaceous fimbriae. These small diancistras are approximately half as smaller than the intermediate-sized diancistras (II) again, measuring 21.4–(23.6)–26.3 x 1.0–(1.3)–1.5 μm, n=10.

Remarks; Hamacantha (V.) levii sp. nov. joins several of the Hamacantha species with three different size classes of diancistras, some of which (e.g. H. (V.) bowerbanki Lundbeck, 1902 and H. (V.) falcula ( Bowerbank, 1874)) have toxas ( Table 2 ). This new species lacks toxas and in spicule composition is closest to H. (V.) atoxa Lévi, 1993 , but it differs from H. (V.) atoxa in its colouration and the size difference and shape of the large diancistras. The smaller two size classes of diancistras are similar in dimensions to those of H. (V.) atoxa , but differ substantially in their shape and are twisted, which is not reported in H. (V.) atoxa .

Figures

FIGURE 1. Sampling sites of Hamacantha species described in this study.

FIGURE 6. Hamacantha (Vomerula) levii sp. nov. A. Holotype QM G339187 fixed on the stem of a dead Keratoisis. B. Closeup of the fixed sponge. C. Lower level of the ectosome showing the folding, where the old supporting bundles of styles have fallen. D. Lower surface of the ectosome showing the tangential ectosomal styles and the embedded diancistras. E. Large diancistras (I). F. Intermediate diancistras (II). G. Small diancistras (III). H. Style. I. Magnified ends of the style depicted in H.