Siphonodictyon occultum, Rützler, Klaus, Piantoni, Carla, Van, Rob W. M. & Díaz, Cristina, 2014

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 : 87-88

Siphonodictyon occultum new species

( Figures 4 e, 40)

Material. Holotype: USNM 1229127, Curlew Bank forereef cave, 18 m; C. Piantoni and M. Parrish col. 23 Aug 2012.

Diagnosis. Cryptic (cave-dwelling) Siphonodictyon with small (25 x 6 mm), gray, well-separated inhalant and exhalant siphons and dull-pointed oxeas approaching the shape of strongyles.

External morphology. Inhalant fistules and exhalant oscular tubes protrude from the rock surface, are well separated from each other and similar in size, 15–27 mm tall, 3–7 mm in diameter. The principal sponge body fills ovoid cavities and crevices, 2–5 mm below the substratum surface and extending at least 6 cm horizontally. Because the collected material was incomplete we could not determine endolithic extension precisely. Inhalant fistules are closed by a pore sieve at the top, the oscular tubes are fully open. The siphons are hard and brittle and gray to purplish in color, although they are in part covered by thinly encrusting coralline algae and sponges; the color becomes nearly white at the top, around the openings. The endolithic choanosome is also grayish white.

Skeleton structure. Oxeas in the siphons are arranged in a unispicular network. This pattern is maintained in the choanosome as well but, here and there, gives way to disorganized placement.

Spicules. Most are slightly bent oxeas with dull points, more or less approaching strongyles. Some are styloid, many have stepped or otherwise malformed points: 220–270 x 7–10 (249 x 9) µm.

Ecology. Only found in one cave on the forereef, 18 m.

Distribution. Belize.

Etymology. The species name refers to the cryptic occurrence of this species, occultus (Latin) = hidden.

Comments. Six species of Siphondictyon are known from the tropical Western Atlantic, that is, S. brevitubulatum Pang , S. cachacrouense Ruetzler , S. coralliphagum Ruetzler , S. ruetzleri (Calcinai, Cerrano & Bavestrello) , S. siphonum (de Laubenfels), and S. xamaycaense Pulitzer-Finali. This new sponge differs from all by the small size and solitary growth of the epilithic structures (fistules) and the relatively large size of almost strongylote oxeas. More study will be needed to determine whether this species is restricted to cave habitats.

Figures

FIGURE 4. In-situ photographs of new sponge species reported in this contribution (measurements in parentheses are picture widths): a, Wigginsia curlewensis (8 cm); b, Phorbas aurantiacus (10 cm); c, Myrmekioderma laminatum (12 cm); d, Niphates arenata (10 cm); e, Siphonodictyon occultum (10 cm); f, Xestospongia purpurea (8 cm); g, Aplysina sciophila (20 cm).