Plakinastrella onkodes Uliczka, 1929

Gómez, Patricia & Calderón-Gutiérrez, Fernando, 2020, Anchialine cave-dwelling sponge fauna (Porifera) from La Quebrada, Mexico with the description of the first Mexican stygobiont sponges, Zootaxa 4803 (1), pp. 125-151 : 145-147

Plakinastrella onkodes Uliczka, 1929

Fig. 13 , Table II.

Synonymy and other records. Plakinastrella onkodes Uliczka, 1929:60 ; Zea 1987:227; Gómez 2002:68; Rützler et al. 2014:13; Calderón-Gutiérrez et al. 2018:10, S3 Table.

Material examined. CNPGG‒1549, CNPGG‒2329, Cenote S-1, La Quebrada anchialine cave, Cozumel , Quin- tana Roo, Mexico (20°26’16.75’’N, 86°59’47.44’’W). Depth 5.6 m, October 23, 2015; coll. F. Calderón-Gutiérrez and German Yáñez.

Description. Small cushion-shaped or irregular specimens, 5‒10 mm high, 6‒8 mm wide; color orange when alive dark brown when in alcohol ( Fig. 13a ). Surface smooth to the eye, slightly wavy, with small star-shaped furrows with contracted central oscules. Consistency firm, only slightly compressible.

Skeleton. ( Fig. 13 b, d ) The ectosomal skeleton is a reticulation of tracts which are packed by small diods (diactinal spicules) in all directions; other diods perpendicular to surface are disposed in a palisade-like arrangement. Altogether, conforming round meshes at the subsurface layer. Choanosomal skeleton dense and confused, spicules of all types in all directions.

Spicules. (Figs. c, e) Diods with a central kink in two or three size categories, 19‒171.6 × <1‒6.5 µm, slim triods 13‒34.6 × 1.3‒2.7 µm (base of rays), and calthrops 15.2‒41.6 × 2.8‒7.8 µm (base of rays) (Table II).

Geographic distribution. All through the Greater Caribbean.

Ecology. Plakinastrella onkodes is commonly found from coral reefs, up to 20 m deep. It has been also found inhabiting marine caves in the Bahamas and Belize ( Slattery et al. 2013, Rützler et al. 2014), and at the anchialine caves La Quebrada and El Aerolito, Cozumel ( Calderón-Gutiérrez et al. 2018). No individuals fell inside the transects of the quantitative survey, indicating a low population size ( Calderón-Gutiérrez et al. 2018).

Remarks. Apparently, spicule sizes of P. onkodes can vary within a wide range of sizes. In the material studied, diods are within the range dimensions except with Zea’s measurements (Table II). Triod sizes are according with Uliczka (1929) and Pulitzer-Finali (1986), but smaller than those from Zea (1987) and Rützler et al. (2014). The calthrops are smaller in size within the material studied than those of the quoted authors. However, the differences in size are most probably owed to the differences in environmental conditions. Two more Plakinastrella species have been reported from marine caves, P. microspiculifera Moraes & Muricy, 2003 from Brazil ( Moraes 2011); and P. copiosa Schulze, 1880 from the Mediterranean ( Pouliquen 1972), not similar to the present species.

Figures

FIGURE 13. Plakinastrella onkodes Uliczka, 1929. a) CNPGG‒1496 habitus (ethanol); b) choanosomal skeleton (cross sec- tion, LM); c) triod and calthrops; d) ectosome in the upper flank; (LM); e) diods (LM).