Oscarella carmela Muricy & Pearse, 2004

Van, Rob W. M., Kaiser, Kirstie L. & Syoc, Robert Van, 2011, Sponges from Clipperton Island, East Pacific, Zootaxa 2839, pp. 1-46 : 8-9

Oscarella carmela Muricy & Pearse, 2004

( Figs 2 B–D)

Oscarella carmela Muricy & Pearse, 2004: 600 , Figs 2–4 .

Material examined. MNHN DCL 4050–A, Jean-Louis Etienne Expédition Clipperton 2004/5, station 42, 8 m, on dead corals, 31–01–2005, 1 specimen.

MNHN DCL 4051–A, Jean-Louis Etienne Expédition Clipperton 2005, station 43, 8 m, on dead corals, 31–01– 2005, 1 specimen.

Description. Soft encrustations on dead corals, with lobate upper surface. Lobes flattened in preservation, clearly demarcated by grooves surrounding slight round elevations of 1–2 mm diameter. The material consists of two separated encrustations on the same coral block ( Fig. 2 B), one 5 cm in widest expansion, the other 2 cm, closely together but apparently separated. Lobes in preserved condition only a few mm high.

Thin sections ( Figs 2 C–D) are 1.4 mm thick and show a strongly folded upper part and large lacunae just above the substrate, as is usual for the genus. Folds in the sections are approx. 0.5 mm in diameter, separating grooves 0.6 mm deep. These folds contain dense concentrations of rounded choanocyte chambers crowded around exhalant canals leading to the lacunae. Folds are covered by a thin pinacoderm. Choanocyte chambers ( Fig. 2 D), ovoid to rounded, 29–55 µm in diameter. Numerous embryos and pre-release larvae ( Fig. 2 C), size up to 350 µm in diameter, are crowded at the bottom of the grooves.

Ecology and distribution. Encrusting dead corals under overhangs and in crevices in shallow reef environment, 8 m; known from Île Clipperton and Central California.

Remarks. Species of this genus are distinguished based on features of the soft tissue, which means properly fixed material is a necessity. Our specimen was ‘postfixed’ after first having been kept in 75% alcohol for four years. Thus, the characters described above are somewhat suspect and may need to be revisited based on adequately fixed material (live material fixed in glutaraldehyde for two days). Notwithstanding this, we believe that the Clipperton material is closest to Oscarella carmela Muricy & Pearse, 2004 described from the Central California coast (Monterey Peninsula), where it encrusts rocks and artificial substrates. Many features of this species appear to conform with our material, including the size of the choanocyte chambers. Differences are subtle: slightly larger upper size of the choanocyte chambers (25–65 µm), larvae are slightly smaller (50–350 µm). A further indication that our material may be conspecific with O. carmela is the fact that this species is known to invade artificial structures, which is characteristic for species with great dispersal capabilities.

Further Oscarella species reported from the Pacific Ocean are: Oscarella tenuis Hentschel, 1909 described from Western Australia (along with O. membranacea Hentschel, 1909 ), and subsequently recorded from North East Australia ( Burton 1934) and an aquarium in Hawaii ( De Laubenfels 1954b). The latter specimen is described as papillate and very thin, choanocyte chambers 30 µm diameter. This is clearly smaller than the sizes found in our material. Likewise, O. stillans Bergquist & Kelly, 2004 from the Philippines, has much smaller choanocyte chambers. Oscarella lobularis ( Schmidt, 1862) was reported from the Pacific end of the Panama Canal ( Panama City, intertidal) by De Laubenfels (1936b). The only relevant descriptive information provided is the size of the choanocyte chambers, given as 25 µm. O. lobularis is a Mediterranean species, subsequently reported from many areas of the world, but these probably form a cryptic species complex ( Muricy & Díaz 2002). Recently, O. malakhovi was described from the NW Pacific ( Ereskovsky 2006). This has much smaller choanocyte chambers and its occurrence in cold water make it unlikely that this could be the same species.

Figures

FIGURE 2. A. Plakinastrella clippertonensis n. sp. habit of holotype, MNHN DCL 4042 – A. B – D. Oscarella carmela Muricy & Pearse, 2004, B. habit of specimen MNHN DCL 4050 – A, C – D. Oscarella carmela Muricy & Pearse, 2004, C. histological cross section showing basal lacunae and embryos, D. detail of the same showing choanocyte chambers separated by peripheral grooves.

FIGURE 3. Plakinastrella clippertonensis n. sp., spicules of holotype MNHN DCL 4042 – A. A. diods, B. microdiods, C. calthrops, D. triods, including ‘ microtriod’ (at right).

FIGURE 4. Paratimea globastrella n. sp., A. habit of holotype ZMA Por. 21202, B. thick section of skeleton showing dominance of globular silica bodies interpreted as modified asters, C. tylostyles, D. centrotylote oxeas, E. large globular aster, F. smaller globular asters showing various stages of aster-derived lobes and spines.