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(Topsent, 1898)

Species Overview

Spiroxya levispira (Topsent, 1898) is an excavating sponge with peculiar and characteristic microscleres, known from southern deep water habitats. Recently, specimens were found off the W coast of Scotland in relatively shallow coldwater corals (82-168 m).

Taxonomic Description

Colour: pale beige.
Shape, size, surface and consistency: Excavating sponge, with exclusively alpha-habit, papillae inconspicuous, flush with the surface, 2-4 mm in diameter, giving access to relatively large ellipsoid cavities, up to approximately 10 mm diameter, filled with pale coloured, off-white or beige, soft tissue.
Spicules: Two size-classes of oxeas, spiral microstrongyles and acanthomicrorhabds. Oxeas I: fusiform, sharply pointed, 186 - 330 x 9-12 µm; oxeas II, anisoxeote, with one end usually rounded or blunt, the other end sharply pointed, 126- 169.0-198 x 4-5 µm; spiral microstrongyles, smooth or faintly microspined, large size variation, 15-138 x 5-6 µm; acanthomicrorhabds, straight, amphiaster-like, usually centrotylote or spined most prominently in the middle, 9 -15 x 1-2 µm).
Skeleton: Radiate arrangement of megascleres at the surface of papillae, with tracts of oxeas lining the cavities and with confused arrangement of spicules in the soft interior mass. Smaller oxeas are concentrated in the surface, larger oxeas in the cavities.
Ecology: Excavating dead Lophelia and Madrepora corals at 82-762 m depth in Scottish waters, elsewhere 5-2165 m. The shallow record is from Mediterranean cave habitats (Pouliquen, 1972), which are known to contain a deepwater fauna.
Etymology: named for the spiral microscleres which appear smooth ('levis') at low magnification (but are often microspined)
Type specimen information: The type specimen is in the Monaco Museum.

Remarks

The species is predominantly reported from southern European localities, Azores, Madeira, Morocco and the western Mediterranean (Topsent, 1898, 1904; Johnson, 1899; Boury-Esnault et al., 1994; Pouliquen, 1972; Rosell & Uriz, 2002; Longo et al., 2005). The species was recently reported from Rockall Bank deepwater coral reefs, in the ocean west of Ireland (Van Soest et al., 2007) and from Mingulay cold water reefs off the coast of W Scotland. Most of the reported specimens show closely similar spicular characters. The Madeira specimen of Johnson (1899 as Scantilla spiralis) was not fully described, but the figures provided by this author make it likely that they concern the same species. A second species of Spiroxya, S. heteroclita Topsent, 1896 is recorded from deep water Lophelia reefs west and south of Ireland (Stephens, 1915; Beuck et al., 2007). This species differs clearly from S. levispira in possessing spirally spined straight strongyles, lacking acanthomicrorhabds, and having oxeas up to 900 µm (Rützler, 2002b).
Source: van Soest & Beglinger, 2009.

Spiroxya levispira