Diplopodospongia macquariensis Sim-Smith & Kelly, 2011, gen. nov.

Diplopodospongia macquariensis gen. nov. sp. nov.

(Fig. 1 H, 5 L–M)

Material examined. Holotype ―QM G331915: NIWA station TAN0803/89, Seamount 8, south of Macquarie Island, Macquarie Ridge (Australian EEZ), 55.381° S, 158.427° E, 504–637 m, 15 Apr 2008. Paratypes ―QM G331916: NIWA Stn TAN0803/102, Seamount 9 Hjort, south of Macquarie Island, Macquarie Ridge (Australian EEZ), 56.242° S, 158.462° E, 790–1025 m, 16 Apr 2008; QM G331917: NIWA Stn TAN0803/98, Seamount 9 Hjort, south of Macquarie Island, Macquarie Ridge (Australian EEZ), 56.246° S, 158.506° E. 676–750 m, 16 Apr 2008.

Type location. Seamount 8, south of Macquarie Island, Macquarie Ridge (Australian EEZ).

Distribution. Seamounts 8 and 9 in the Macquarie Ridge.

Description. Very thinly encrusting sponge, <1 mm thick, growing on dead coral or rock (Fig. 1 H). Surface smooth, soft and friable to the touch, no visible oscules; surface wrinkled. Colour in ethanol beige to light mustard brown.

Skeleton. Ectosome a dense layer of diplospinorhabds, which are generally vertically disposed. The choanosome consists of loose bundles of anisoxeas that emerge from the base to form rough brushes in the ectosome. Microscleres are scattered throughout the choanosome.

Megascleres (Fig. 5 L, Table 3)― Anisoxeas, straight, centrally thickened, centrally tylote; 442 (394–477) x 9 (7–11) µm.

Microscleres (Fig. 5 M, Table 3)― Diplospinorhabds, symmetrical, double-ended, with generally symmetrical ends that are separated by a short shaft. The base and apex are single spines, and the basal and apical whorls consist of four long smooth, bifurcate spines, separated by a smooth thick shaft. Protodiplospinorhabds were rare. Those that were found under light microscopy were linear, shaped like a bow-tie; 27 (20–31) µm long x 23 (20–27) µm wide.

Substrate, depth range, and ecology: Growing on the surface of oculinid corals between 500 and 1000 m.

Etymology. Named for the type location, the Macquarie Ridge.

Remarks. Diplopodospongia macquariensis gen. nov. sp. nov. is superficially quite similar to D. rara gen. nov. sp. nov. in the shape of the diplospinorhabds. However, there are several key differences that we believe are not ecophenotypic variations. The megascleres of D. macquariensis gen. nov. sp. nov. are considerably longer and different in shape; they are centrally thickened with polytylote or centrotylote swellings, and they are very straight, whereas those of D. rara gen. nov. sp. nov. are noticeably curved, almost sinuous. While the diplospinorhabds of D. macquariensis gen. nov. sp. nov. are similar in general style of ornamentation, the bifurcate spines are much longer, and the shaft shorter, making the spicule less compact. The apex and base are frequently only composed of a single robust spine, compared to three spines in D. rara gen. nov. sp. nov. The gross morphology and colouration of the two species also differs; D. rara gen. nov. sp. nov. is more thickly encrusting and white in ethanol, whereas D. macquariensis gen. nov. sp. nov. is more thinly encrusting and beige in ethanol.