Stelletta

Cárdenas, Paco, Menegola, Carla, Rapp, Hans Tore & Díaz, Maria Cristina, 2009, Morphological description and DNA barcodes of shallow-water Tetractinellida (Porifera: Demospongiae) from Bocas del Toro, Panama, with description of a new species, Zootaxa 2276, pp. 1-39 : 20-22

Stelletta sp.

( Figure 10 )

Material. ZMBN 81643, Solarte lagoon (9° 18.35 N, 82° 10.39 W), on mangrove root, 1 m depth.

Additional material examined. Stelletta soteropolitana Cosme & Peixinho, 2007, UFBA-POR 500, holotype, Salvador, Bahia State, Brazil, <10 m.

Outer morphology ( Fig. 10 A–B). Massive, sub–globular sponge, 10 cm high, with a diameter of 9 cm. Surface color alive is dark–purple to whitish. Choanosome color is cream In ethanol, cortex and choanosome are grayish. One large oscule (diameter: 2 cm) with a contractile membrane is on the top surface. Under the oscule is a large cloaca (6 cm deep) with cribriporal exhalant apertures. Unconspicuous cribriporal pores are evenly distributed, each pore is 100–1000 µm large. Slightly–compressible, rugose surface with irregular ridges, grooves and knobs (2–7 mm high). Mussels and oysters are embedded in it. A second specimen was observed (but not collected): it was about twice the size of ZMBN 81643, with two oscules.

Skeleton ( Fig. 10 C–D). Dense radial bundles of plagiotriaenes and anatriaenes, especially near the surface. Their cladomes are often found at or beyond the surface of the sponge. There is a slightly differentiated cortex, not visible with the naked eye, except for the pigmentation. Bundles of megascleres are looser under the cortex and triaenes less abundant. Acanthotylasters, oxeas I and II are abundant throughout the sponge.

Spicules ( Fig. 10 E–G). Megascleres: (a) oxeas I, large, slightly bent or straight, length: 1080– 1236.3 – 1440 µm; width: 18– 24.4 –32 µm. (b) oxeas II ( Fig. 10 E), smaller, with very thinly pointed ends, almost whip–like, generally with a bend or a double bend, length: 303– 724.7 –1000 µm; width: 3– 9.5 –14 µm. (b) plagiotriaenes ( Fig. 10 F), with rare dichotriaenes, rhabdome can have a straight pointed or whip–like end, rhabdome length: 511– 850.9 –1056; rhabdome width: 13– 31.5 –39 µm; clad length: 50– 121.3 –152 µm. (c) anatriaenes ( Fig. 10 G), common but less frequent than plagiotriaenes, and rare dichoanatriaenes, with depressed apex, rhabdome length: 716– 1363.2 –2280 µm; rhabdome width: 8– 21.7 –29 µm; clad length: 38– 65.1 –91 µm. Microscleres: (d) acanthotylasters ( Fig. 10 H), 5–8 actines with scarce spines, actine is only slightly tylote, one single spine at the tip of each actine, diameter: 9– 13.5 –20 µm.

Habitat in the Bocas del Toro region. Mangrove roots, rare, 1 m depth.

Distribution. Panama (this study).

Remarks and discussion. This species appears to be rare in Bocas del Toro. We only sighted two specimens during our survey in 2007, both a few meters apart in Solarte lagoon. At this time, we only took a small piece from ZMBN 81643. In July 2009, both specimens were still there, but were slightly bigger and bleached ( Fig. 10 B). The bleaching could be due to shading from the algae growing around it, because when we finally collected ZMBN 81643 and kept it alive alone in an open tank, it started to gain back some purple colouration.

At present there are four known species of Stelletta with tylasters in the Caribbean ( S. fibrosa , S. variabilis , S. kallitetilla and S. pudica ) and three in Brazil ( S. anancora , S. beae Hajdu & Carvalho, 2003 and S. soteropolitana ). Of these, only the three Brazilian species share long clads (average of clad length> 100 µm) with our Bocas del Toro specimen. However, when compared with Stelletta sp., S. anancora has (i) only one category of oxeas, (ii) 2–3 triaene sizes, (iii) no anatriaenes and (iv) no dense accumulation of megascleres in its cortex; S. beae has (i) shorter plagiotriaenes (rhabdome length ca 490 µm) with longer clads (ca 200 µm), (ii) shorter anatriaenes with reduced clads (ca 23 µm), (iii) one size of oxea, and (iv) smaller acanthotylasters (ca 11 µm). When it comes to S. soteropolitana it has i) plagiotriaenes twice the size of those in Stelletta sp., ii) protriaenes and iii) no anatriaenes. As we have already shown for S. fibrosa , anatriaenes can be present or absent in the same species, and the missing anatriaenes in S. soteropolitana , at the present time, cannot be used to distinguish the species from our S. sp. The protriaenes found in S. soteropolitana could simply be plagiotriaenes that are more forward oriented. Also, it is important to stress that S. soteropolitana is described from a single specimen and therefore, we have no data on its intra-specific morphological variation, especially concerning spicule sizes. To conclude, we cannot exclude S. soteropolitana as being conspecific with our specimen but in our opinion more data is required to settle this matter.

Figures

FIGURE 10. Stelletta sp. [ZMBN 81643]: A. Specimen in situ on mangrove root, August 2007. Notice large oscule leading to a cloaca. Scale: 2 cm; B. Bleached specimen maintained alive in a tank, July 2009. Scale: 2 cm; C. Cross – section showing the skeletal architecture. Scale: 1 mm; D. Close-up of cross-section showing bundles of triaenes at the surface of the sponge. Scale: 1 mm; E. Oxea II. Scale: 100 µm; F. Plagiotriaenes. Scale: 100 µm; G. Anatriaene and tylaster. Scale: 20 µm; H. Tylaster. Scale: 4 µm.