Chondropsis subtilis, Calcinai, Barbara, Bavestrello, Giorgio, Bertolino, Marco, Pica, Daniela, Wagner, Daniel & Cerrano, Carlo, 2013

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 : 12-14

Chondropsis subtilis n. sp.

( Fig. 6 A–H) ( Tab. 3 )

Holotype material. MSNG 56260: sample Bugor 504: Indonesia, North Sulawesi, Manado Tua Island, Negeri, 15 m, September 2007.

Paratype material. MSNG 56261: sample Siladen Village: Indonesia, North Sulawesi, Siladen Island, 10 m, October 2008.

Comparative material: Chondropsis wilsoni Dendy, 1895 holotype material BMNH, 1902.10.18.155-156-157 (three slides).

Diagnosis. Chondropsis subtilis is characterised by a surface that is covered by a reticulated pattern of fine sand, a main skeleton of longitudinal, ascending tracts of sand, strongyles and foreign spicules embedded in spongin; spicules are thin strongyles (2 µm) as megascleres and small sigmas as microscleres.

Description. The sponge (holotype) encrusts a colony of Carijoa riisei as a pellicle up to 0.5 mm thick ( Fig. 6 A, B), leaving only the polyp openings free. The holotype occurs on several branches of the coral, up to 14 cm long ( Fig. 6 C). The paratype occurs on several inter-crossing branches of C. riisei covered by numerous other epibionts (bryozoans, vermetids, foraminifera). Consistency soft and compressible. Surface microconulose due to protruding choanosomal bundles; in some portions of the sponge surface sand and spicules create a fine network ( Fig. 6 D). In the paratype the surface is collapsed, the conules are more prominent and the sponge surface is strongly shaggy. The colour is pink salmon in situ ( Fig. 6 A, B), whitish in ethanol ( Fig. 6 C).

Skeleton. Ectosomal skeleton of scattered, tangential strongyles, sand and abundant foreign spicules. A regular network of polygonal to circular meshes, about 100 µm in diameter, is evident on the sponge surface ( Fig. 6 D); in some parts of the sponge, the surface consists of an homogeneous layer of sand, foreign spicules and strongyles ( Fig. 6 E) and the regular pattern of sand is not evident. Choanosomal skeleton of longitudinal, ascending tracts of spongin (70–125 µm in diameter), embedded sand grains, strongyles and foreign spicules connected by debris and transverse strongyles; they sometimes branch dichotomously reaching the ectosome ( Fig. 6 F). Strongyles from the longitudinal tracts extend beyond the surface thus making it microhispid ( Fig. 6 F).

Spicules. Abundant strongyles, straight and very thin, ( Fig. 6 G), with a central black canal, 142.5 – 180 x 2 µm. Sigmas ( Fig. 6 H) “C” shaped very thin, abundant and “S” shaped rare, 13.5 – 18.5 μm. Refer to Tab. 3 for complete measurements.

Remarks. The in situ photograph of the holotype shows a massive sponge with scattered oscules close to the colony of Carijoa riisei ( Fig. 6 B) and spreading over the octocoral. The massive sponge has the same colour as the epibiontic one described above. They also share similar surface features. We collected only the epibiontic portion but it is very likely that the species is also able to grow in a massive form.

All species of Chondropsis have been described from the Indo-Pacific (van Soest et al. 2011). Among these, the species with spicular complement similar to C. subtilis n. sp. (strongyles and sigmas as the unique type of microscleres) are C. ceratosus Kirkpatrick, 1900 , C. chaliniformis Lendenfeld, 1889 , C. columnifera Dendy, 1895 , C. confoederata ( Lamarck, 1814) , C. kirkii ( Bowerbank, 1841) , C. lamella ( Vacelet, Vasseur & Leví, 1976) and C. wilsoni Dendy, 1895 . Chondropsis australis ( Dendy, 1896) differs in having isochelae in addition to sigmas. The remaining species lack microscleres. Chondropsis ceratosus , C. chaliniformis and C. columnifera differ from the new species mainly in having larger sigmas (30–50 μm, 30 μm and 35 μm respectively). Chondropsis kirkii has very small sigmas (5 μm). Chondropsis lamella differs in having two size categories of sigmas (25–30 μm and 12 μm).

The examination of the holotype of C. wilsoni reveals that it differs from the new species in having: i) strongyles or tylotes, with irregular extremities, as megascleres (180 x 2.5 μm), ii) the distribution on the surface of small, scattered exogenous material, without a sandy dermal reticulation, and iii) tracts of strongyles in the choanosome being perpendicular to the surface without tangential, connecting strongyles; these tracts of spicules end in tufts. Chondropsis confoederata differs in having flexuous or bent strongyles (140 – 160 x 1 – 3 μm) and a choanosomal skeleton of spongin fibres without clear orientation.

Etymology. Named after the latin “ subtilis ”, meaning thin; referring to its very thin strongyles.

Figures

FIGURE 6. Chondropsis subtilis n. sp. A – B, Living sponge encrusting Carijoa riisei in situ. Note in B the pink massive sponge close to C. riisei might be the holotype of this species; C, Holotype encrusting several branches of C. riisei; D, Sand and spicules creating a fine and regular network on the sponge surface; E, Sponge surface showing a homogeneous layer of sand, foreign spicules and strongyles; F, Choanosomal skeleton of ascending tracts of spongin, embedded with sand grains, strongyles and foreign spicules; G, Straight and very thin strongyle; H, Very thin sigmas.

Tables

TABLE 3. Spicule dimensions in µm of Chondropsis subtilis n. sp.

	Strongyles	Sigmas
Holotype MSNG 56260	142.5 – (160.4 ± 6) – 170 x 2	13.5 – (15.3 ± 1.3) – 18.5
Paratype MSNG 56261	152.5 – (166.9 ± 6.5) – 180 x 2	13.5 – (15 ± 10.9) – 16.5