Spirastrella mollis Verrill, 1907

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 : 38-39

Spirastrella mollis Verrill, 1907

( Figure 21 )

Synonymy and references. Spirastrella cunctatrix Schmidt, 1868 : Wiedenmayer (1977): 162, fig. 161, pl 33: 8; Spirastrella mollis Verrill, 1907 : Rützler (1986): 122, pl. 33, color pl. 4.14. Spirastrella hartmani Boury-Esnault, Klautau, Bézac, Wulff & Solé-Cava, 1999: 48 , figs. 2A, 4A, B, E.

Material. USNM 1228963, Carrie Bow Cay back reef, near reef rest, underside of Acropora palmata coral rubble. 0.3 m; K. Ruetzler col. 23 Apr 1974. USNM 1228964, Carrie Bow Cay South reef, Acropora palmata coral plates in exposed zone behind reef crest, 1 m; K. Ruetzler col. 6 Mar 2006. USNM 1228965, 1228966, Carrie Bow Cay South reef, Acropora palmata coral plates in behind reef crest, 1 m; K. Ruetzler col. 13 Mar 0 9. USNM 1228967, Carrie Bow Cay West, under concrete dock, 0.5 m; K. Ruetzler col. 18 Aug 2012.

Comparative material examined: USNM 30487 Spirastrella mollis Verrill, Little Bay cave, Harrington Sound, Bermuda, 5 m; W. Sterrer col. 24 Jan 1980; USNM 31914 Spirastrella mollis Verrill, Burchalls Cove cave, Bermuda, 17 m; C. Cardellina col. Jun 1981.

Additional material (examined in the field (09-17), not preserved: Twin Cays, Sponge Haven, undercut on mangrove peat, 1 m; M. C. Diaz col. 8 Sep 2009.

External morphology. Fleshy crusts, up to 10 mm thick, covering 5–40 cm 2 of the substratum. The surface is rough to the touch and, under water when undisturbed, shows vein-like swellings of exhalant canals leading toward the elevated oscula. Oscula, 1–4 mm diameter. Color in life salmon, pinkish red to ochre, to dull reddish brown.

Skeleton tructure. Tracts of tylostyles lead from the substratum to the sponge surface where they may protrude in brushes. Spirasters are forming a cortex as well as a dense layer at the base; in the choanosome in between they are loosely scattered.

Spicules. Tylostyles straight, most with slightly oblong, ovoid heads, some heads subterminal: 235–520 x 4–15 (396 x 11) Μm; spirasters I, with an axis bent once or twice, with strong spines at the ends and on the convex side of the bends: 20–50 (39) Μm; spirasters II, small structures with generally just one axial bend, with bifid (branched) and multifid spines at either end and on the convex side of the axis, a few amphiasters or transitions toward that state: 5–11 (9) Μm.

Ecology. Common on the lower surfaces of platy coral rubble, in crevices and caves of the forereef, and on ceilings of mangrove-peat undercuts; 0.3– 25 m.

Distribution. Bermuda, Bahamas, and Caribbean.

Comments. From its outside color and morphology, and its ecology, this sponge resembles (and was oftentimes confused with) Spirastrella cunctatrix , a Mediterranean species. However, Boury-Esnault et al. (1999) recognized, in addition to biogeographical distance, differences in spiculation, mainly the absence of complex spination on the smallest spirasters present in S. mollis ; therefore, these authors introduced a new species, S. hartmani , mainly because they did not have access to sufficient material of S. mollis from the type locality, Bermuda.

Figures

FIGURE 21. Spirastrella mollis, spicules (SEM): a, tylostyles; b, spirasters I; c, spirasters II / amphiasters.