Radiella sclera, Ekins & Erpenbeck & Wörheide & Hooper, 2023

Ekins, Merrick, Erpenbeck, Dirk, Wörheide, Gert & Hooper, John N. A., 2023, Deep Water Polymastiidae (Porifera, Polymastiida) from the South West Pacific, Zootaxa 5369 (1), pp. 57-88 : 65-69

Radiella sclera sp. nov. Ekins, Erpenbeck & Hooper

urn:lsid:zoobank.org:act:735298BB-B9BA-4A42-A972-12779E97830A

Figures 1 & 5 , Table 3

Type material: Holotype QM G316333 , Lord Howe Plateau , Pacific Ocean Seamounts, Australia, -34.2315, 162.6765, 515–700 m, Sherman Sled, Coll. NORFANZ expedition on RV Tangaroa , 85-014, MF336, 26/V/2003.

Etymology: named for its texture, sclera L., hard f.

Diagnosis: A very hard Radiella species anchored to rock by choanosomal tracts of tylostyle forming root like processes. The sponge lacks a fringe and a purely radial skeleton, having instead a multilayered complex choanosomal skeleton.

TABLE 3. (Continued)

Morphology: The sponge is a hard incompressible, cream coloured low flat to convex cushion 23.5 mm in dimeter and 4.53 mm in height ( Fig. 5 A ). The sponge was presumably attached to some hard substrate (possibly sunken pumice), as stain marks are apparent on the lower surface and the base of spicule bouquets emerge from the body to form root-like processes ( Fig. 5 B ). There were no apparent papillae or oscular structures present on the upper surface. In cross section the choanosome is cream in colour, whilst the dense spicule ectosome is colourless ( Fig. 5 B ). The surface of the ectosome is cream in colour, but this is most likely due to sediment.

Skeleton: The ectosomal skeleton is a dense palisade of principal styles arising from bouquets formed in the choanosome ( Fig. 5 D ). The choanosome is a confused array of the two smaller sizes of tylostyles, often in small bundles of the intermediate sized tylostyles ( Fig. 5 C ). Bouquets of the principal styles originate exterior to the underside of the sponge body where they function as root-like anchoring processes. These bouquets radiate up through the choanosome all the way up to the ectosome ( Fig. 5 C, D ). The principal tylostyles that form the bouquets on the upper ectosome are also the same spicules that form the radial thin lower ectosomal skeleton ( Fig. 5 C ), which ascends on the periphery to form another bouquet ( Fig. 5 D ). The small and intermediate tylostyles are present throughout the choanosome.

Spicules: The megascleres are composed of three overlapping sizes of tylostyles, which all represent a gradation. As the tylostyles increase in length, they also proportionally decrease in width. The two smaller sizes of tylostyles are much thicker towards the point, whilst the largest tylostyles are slightly thicker towards the head. Principal tylostyles are 913–(1140)–1450 × 12.0–(18.8)–30.0 μm, n=46 ( Fig. 5 E, F ). The intermediate tylostyles are 557– (744)–980 × 8.4–(13.9)–21.4 μm, n=34 ( Fig. 5 G, H ), whilst the small tylostyles are 245–(416)–554 × 5.4–(11.0)– 15.7 μm, n=47 ( Fig 5 I ).

Distribution: Known only from seamounts in the Lord Howe Plateau, bathyl depths.

Ecology: Attached to a hard substrate, most likely rocks

Molecular data: no unambiguous 28S-C region barcode could be generated from this species.

Remarks: This new species lacks the very large fringing styles that are normally obvious in species of the genus Radiella . This species differs from S. australis Lévi, 1993 in being much larger, lighter in colour, with a harder, denser and incompressible texture. Furthermore, our new species lacks the purely radial skeleton found in S. australis , but has a multilayered complex choanosomal skeleton instead. It also lacks the large fringe tylostyles as well as the raphides found in the New Caledonian specimens.

Figures

FIGURE 1. Distribution of the specimens of species described herein as they were collected during the expeditions.

FIGURE 5. Radiella sclera sp. nov. Holotype QM G316333. A–B. Upper and lower surfaces of the preserved holotype. C–D. Light micrographs of sections through the radial thin ectosomal skeleton (C), and bouquets of tylostyles in the ectosome (D). E. Principal tylostyle. F. Enlarged view of principal tylostyle. G. Intermediate tylostyle. H. Enlarged view of intermediate tylostyle. I. Small tylostyle.