Plakinastrella clippertonensis, VAN SOEST, KAISER & VAN SYOC, 2011

Cruz-Barraza, José Antonio, Vega, Cristina & Carballo, José Luis, 2014, Taxonomy of family Plakinidae (Porifera: Homoscleromorpha) from eastern Pacific coral reefs, through morphology and cox 1 and cob mtDNA data, Zoological Journal of the Linnean Society 171 (2), pp. 254-276 : 269-270

PLAKINASTRELLA CLIPPERTONENSIS VAN SOEST, KAISER & VAN SYOC, 2011 ( FIGS 2F , 7 )

Material examined

LEB-ICML-UNAM-2034, Clipperton Island, 10°17′30″N, 109°14′59″W, 14 m depth, 28.ii.2005 .

Description

Encrusting to cushion-shaped sponge (0.5 mm to up to 1 cm thick), covering an area of 8.4 × 3.5 cm. The surface is smooth to the naked eye, but rugose under the stereoscope. It also possesses homogeneously distributed subectosomal spaces ( Fig. 2F ). Oscula are circularshaped and slightly elevated from the surface, measuring 0.2 to 0.5 mm in diameter. The consistency is compressible but fragile. The colour is beige in preserved specimens.

Spicules: diods, triods, and calthrops. Diods are thin, widening to the middle shaft where there are one or two short bends ( Fig. 7A ). Diods are in a wide size range; they measure 10–(44.8)–70 μm long and 0.25–(1.35)– 2.5 μm wide. Triods rays are mostly equidistant, thin but irregularly straight, sometimes with one ray smaller than the other two ( Fig. 7B ). The rays measure 3.75– 25 μm long; [total spicule length 7.25–(13.43)–42.5 μm]. Calthrops can be equidistant or with one longer ray ( Fig. 7C ). The rays measure 3.75–22.5 μm long [total spicule length 7.5–(25.19)–42.5 μm].

Skeleton: the ectosomal skeleton consists of a tangential alveolar layer (20–30 μm in thickness) of spicule tracts (mainly diods), forming rounded meshes of 20– 90 μm in diameter ( Fig. 7D ). The choanosomal skeleton is a dense structure formed mainly by diods, triods, and rare small calthrops. which form an irregular to alveolar pattern, with meshes of 30 to 55 μm in diameter ( Fig. 7E ). Choanosomal spaces are very abundant and vary from 70 to 500 μm in diameter.

Ecology and distribution

The species was described from Clipperton Island on dead corals in deep reef habitat (55 m) ( van Soest et al., 2011). In the present study it was found on the same island under rock and corals at 14 m depth .

Remarks

The species was recently described by van Soest et al. (2011). Our specimen agrees in general aspects with the original description, although subtle differences are present.

The specimen described by van Soest et al., 2011, is cake-shaped, 1 cm thick; although we only analysed a small fragment, our specimen was cushion-shaped and about 1 cm thick ( Fig. 2F ). The original description also mentioned the skeleton as dense mass of diods and triods arranged around the aquiferous system, which is similar to our specimen ( Fig. 7E ), although we also found a not well-defined alveolar pattern in some sections of the sponge body. The ectosomal alveolar skeleton is similar too, although with rounded meshes slightly smaller in our specimens (50–100 μm vs. 20–90 μm, respectively). Diods and triods present a very similar size (diods: 4–75 μm in original description vs. 10–70 μm in our specimen; triod ray: 3.75– 25 μm vs. 5–33 μm, respectively). However, simple calthrops are smaller than in our specimen (9–15 μm vs. 3.75–22.5 μm, respectively). In general, calthrops are very rare and only 12 were measured in the original description; we found a large number of spicules and a substantial range of measurements. To date, only two specimens of this species have been described. When more specimens are described, it will probably be possible to establish clearly the limits and ranges of spicule sizes.

Figures

Figure 2. External morphologies of plakinid species from the eastern Pacific. A, B, Plakina muricyae sp. nov. C, i, Plakina paradilopha sp. nov.; ii, Plakina muricyae sp. nov. D, Plakortis clarionensis sp. nov. E, Plakortis albicans Cruz-Barraza & Carballo, 2005. F, Plakinastrella clippertonensis van Soest et al., 2011.

Figure 7. Scanning electron microscopy images of spicules and skeletal structure of Plakinastrella clippertonensis van Soest et al., 2011. A, diods. B, triods. C, simple calthrops. D, tangential view of the ectosome. E, transversal view of the choanosome.