Stelletta solidissima ( Wilson, 1902 )

Rützler, Klaus, Piantoni, Carla, Van, Rob W. M. & Díaz, Cristina, 2014, Diversity of sponges (Porifera) from cryptic habitats on the Belize barrier reef near Carrie Bow Cay, Zootaxa 3805 (1), pp. 1-129 : 20-22

Stelletta solidissima ( Wilson, 1902)

( Figure 10 )

Synonymy and references. Coppatias solidissima Wilson, 1902: 387 . Stelletta Schmidt, 1862 : Uriz (2002a): 110, fig 1.

Material. USNM 1228912, Carrie Bow Cay forereef slope, underside of coral rock, 30 m; K. Ruetzler col. 26 Apr 1974. USNM 1228913, Carrie Bow Cay North channel, under coral rock, 6 m; K. Ruetzler col. 23 May 1979. USNM 1228914, Carrie Bow Cay South reef, Acropora palmata coral plates in exposed zone behind reef crest, 1 m; K. Ruetzler col. 6 Mar 2006.

Additional Material Examined: USNM 7659 (holotype) Coppatias solidissima Wilson, 1902 : Coral bottom, Sail Rock, off St. Thomas ( U. S. Virgin Islands), 36– 41 m.

External morphology. Thin cushions covering up to 70 cm 2, up to 6 mm thick. Firm consistency, smoothlooking surface but rough to the touch; oscula (1–3.5 mm), irregularly dispersed, alternating with groups of small pores (ostia). Color light to medium gray.

Skeleton structure. Large oxeas in radial position near the surface (including some very rare triaenes), some disorganized, particularly deeper in the choanosome. Asters are concentrated in the ectosome, microxeas dispersed throughout the body.

Spicules. Large oxeas, curved and with sharp tips, a few are strongyloxeote modifications. Smaller oxeas (but not in a different size class) may be double-bent in opposite directions. Oxea sizes: 630–1450 x 8–49 (1104 x 37) µm; rare pro- and orthotriaenes (only found in specimen USNM 1228913): 540–700 x 80 –158 µm (overall length x width), 23–79 µm, length of clads (n=6); microxeas, stout, thickest in the center and with rounded points, some approaching strongyles; microspined, except some have smooth center portion (about 15–20% of the length may be smooth): 55– 90 x 3–5 (73 x 6) µm; microspined strongylasters, with small center and stout, spiny rays: 8–10 (8) µm; microspined oxyasters, with slender, pointed rays: 4–8 (7) µm.

Ecology. Cryptic, on the lower surface of coral rock, 1–30 m; the holotype of this species was dredged from coral bottom, 36– 41 m.

Distribution. Caribbean (so far only from U. S. Virgin Islands and Belize).

Comments. Uriz (2002a) and the World Porifera Database (van Soest et al., 2013b) consider this species to belong to Stelletta , based on the original describer’s observation that triaene spicules were seen among the cortical oxeas. Upon reexamination of Wilson’s type material we could not detect triaenes, nor were any found in the present specimens except in one (USNM 1228913), indicating that this spicule type is rare in the species. Nevertheless, the genus transfer seems appropriate. The original description mentions “smooth” microxeas, but we could determine that they were microspined, just like the ones in our specimens. A similar species, Melophlus hajdui , was described by Moraes (2011) from oceanic islands off Brazil; it seems to lack triaenes (hence, assignment to Melophlus ) and differs by the shorter and thinner oxeas and by microxeas that are evenly microspined over their entire lengths.

It is possible that, owing to the presence of microspined rhabds, this species needs to be transferred to Ecionemia or Stellettinopsis (see Kelly & Sim-Smith, 2012). However, we prefer to reserve this action for a more comprehensive revision because earlier work, lacking access to SEM, may not have been able to discern the various degrees of microspination in relevant species.

Figures

FIGURE 10. Stelletta solidissima, spicules (SEM): a, oxeas; b, triaenes; c, microspined microxeas; microspined strongylasters and oxyasters.