Spirastrella cf. cunctatrix Schmidt, 1868

Calcinai, Barbara, Bavestrello, Giorgio, Bertolino, Marco, Pica, Daniela, Wagner, Daniel & Cerrano, Carlo, 2013, Sponges associated with octocorals in the Indo-Pacific, with the description of four new species, Zootaxa 3617 (1), pp. 1-61 : 9

Spirastrella cf. cunctatrix Schmidt, 1868

( Fig. 4 A–G)

Examined material. Sample HL 162: Vietnam, Hang Trai Island, Hang Du II Lake, 5 m, 26 April 2004.

Description. The sponge, about 1 mm thick, covers the basal stolons and the proximal portion of a colony of Carijoa riisei , as well as a bivalve shell (24 cm 2) where the octocoral colony is settled ( Fig. 4 A). The surface is smooth, slightly pink in ethanol, with evident subectosomal canals.

Skeleton. Spirasters II are concentrated in the ectosome forming a thick superficial crust ( Fig. 4 B). Choanosome with scattered spirasters I and II; tylostyles are grouped in multispicular tracts with tyles towards the substrate ( Fig. 4 C) and tips protruding beyond the surface.

Spicules. Straight tylostyles with hastate tips and generally rounded heads ( Fig. 4 D, G), 225 – (341.5 ± 66.9) – 450 x 5 – (8.5 ± 2.3) – 10 μm, with evident axial canal starting from the head. Spirasters in two categories: spirasters I large, with thick, slightly bent axis and conical large spines ( Fig. 4 E, G), 30.5 – (46.3 ± 6.9) – 60.5 x 5 – (7.5 ± 1.3) – 10 μm, numerous spicules have a straight and thin axis; spirasters II small, with spiralled axis or rabd-like with straight axis; numerous intermediate forms ( Fig. 4 F, G), 5 – (8.7 ± 1.4) – 12.5 μm.

Distribution and remarks. The spicule shape of the Vietnamese sample and the skeletal organisation are very similar to S. cunctatrix Schmidt, 1868 as described and illustrated by Rützler (2002) (see Fig. 5 : 223). The holotype has tylostyles with oval or rounded heads, 480 x 8 μm in length on average; small spirasters of 10 – 25 x 5 – 23 μm and large spirasters of 28 – 50 x 23 – 35 μm ( Rützler, 2002) slightly larger than those of the Vietnamese specimen. Spirastrella cunctatrix was originally described from the Mediterranean Sea, and later recorded also in the Indo- Pacific area (Mergui-Burma Archipelagos ( Carter 1887), Hong Kong (van Soest 1982), Madagascar ( Vacelet & Vasseur 1971), the Red Sea ( Lévi 1965), and Vietnam ( Azzini et al. 2007)) but its distribution has to be considered restricted to the Atlanto-Mediterranean area (van Soest et al. 2011). Further molecular studies could clarify its cryptogenic nature. The species was always described as a thin encrusting sponge, with the exception of the massive sponge record from the Red Sea ( Lévi 1965).

Figures

FIGURE 4. Spirastrella cf. cunctatrix Schmidt, 1868. A, Sponge encrusting Carijoa riisei on a bivalve shell; B, Spirasters II concentrated in a superficial crust; C, Tylostyles grouped in multispicular tracts and spirasters I and II scattered in the sponge tissue; D, Tylostyle; E, Spirasters I; F, Spirasters II; G, Tylostyle with spirasters I and II.

FIGURE 5. Batzella arauntiaca (Lévi, 1958). A, Sponge on Carijoa riisei in situ. B, Choanosomal skeleton of small bundles of strongyles; C, Straight and very thin strongyle, with close up of the tips.