Hymedesmia (Stylopus) perlucida, 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 : 25

Hymedesmia (Stylopus) perlucida n. sp.

( Fig. 15 A–G)

Holotype material. MSNG 56264: sample Bugor 511: Indonesia, North Sulawesi, Nain Island, Jalan Masuk, 17 m, 9 September 2007.

Diagnosis. Hymedesmia (Stylopus) perlucida n. sp. is characterised by a single category of acanthostyles and by fusiform isotornotes.

Description. Very thin encrusting sponge (about <1 mm thick) growing on Paratelesto rosea ( Fig. 15 A–C); only the anthocodiae are free from sponge cover ( Fig. 15 C). The holotype covers a portion of a Paratelesto colony that is about 8 cm long ( Fig. 15 B). Surface is macroscopically smooth. The consistency is gelatinous. Transparent in situ ( Fig. 15 A) and in ethanol ( Fig. 15 B), so that the red colour of the octocoral is visible through the sponge tissue; white in dried state ( Fig. 15 C).

Skeleton. The ectosomal skeleton consists of confused plurispicular tracts and scattered tornotes. The choanosomal skeleton consists of single acanthostyles erect on the coral surface and paucispicular tracts of tornotes ( Fig. 15 D, E).

Spicules. Isotornotes straight, fusiform, gradually thinner towards the extremities ( Fig. 15 F), 147.5 – (156.5 ± 7.8) – 170 x 2.5 μm. Acanthostyles with small spines concentrated on the head and scarce along the shaft ( Fig. 15 G), 110 – (131.7 ± 14.7) – 155 x 2.5 – (3.3 ± 1) – 5 μm.

Remarks. Among the nine species of Hymedesmia (Stylopus) of the Indo-Pacific area (van Soest et al. 2011), those closest to this new species are H. (S.) parvispicula Burton & Rao, 1932 and H. (S.) australiensis ( Hentschel, 1911) , both of which also have tornotes and acanthostyles in a single category. The other known species differ in the larger size of the spicules: H. (S.) acerata ( Topsent, 1904) has tornotes of 460–480 μm, and acanthostyles of 140–380 μm; H. (S.) dendy Burton, 1930 has tornotes of 700 x 16 μm and tylostyles of 2 mm and acanthostyles of 120–240 μm; H. (S.) indivisa Topsent, 1928 has tylotes of 420–540 μm and acanthostyles of 210–595 μm; H. (S.) obtusa Topsent, 1904 has acanthostyles of 130–230 μm and polytylote tylotes of 280 μm. H. (S.) australis ( Bergquist & Fromont, 1988) , H. (S.) lissostyla ( Bergquist & Fromont, 1988) and H (S.) oculifera ( Hentshel, 1911) have two categories of acanthostyles.

In H. (S.) parvispicula tornotes vary in shape from strongylote to amphytylotes; their size is also bigger (210 x 3 μm). Hymedesmia (S.) australiensis differs from the new species especially in the shape of the tornotes, which are characterised by swollen extremities, and in their size (176 – 192 x 2 μm).

Etymology. Named after the transparent colour of living tissues.

Figures

FIGURE 15. Hymedesmia (Stylopus) perlucida n. sp. A, Sponge growing on Paratelesto rosea in situ; B, Holotype encrusting P. ro s e a; C, Close up of P. ro s e a showing the anthocodiae free from sponge; D, Choanosomal skeleton with paucispicular tracts of tornotes; E, Schematic diagram of the sponge skeleton standing to a couple of sclerites; F, Isotornote and close up of the tip; G, Acanthostyle with magnification of the head and tip.