Plakinastrella stinapa, Van Soest & Meesters & Becking, 2014

Van Soest, Rob W. M., Meesters, Erik H. W. G. & Becking, Leontine E., 2014, Deep-water sponges (Porifera) from Bonaire and Klein Curaçao, Southern Caribbean, Zootaxa 3878 (5), pp. 401-443 : 405-406

Plakinastrella stinapa new species

Figures 2a–e , 3a–e

Material examined. Holotype: RMNH Por. 9252, Caribbean Netherlands, Bonaire, locality ‘ Cargill’ (Dive 4), 12.08°N 68.2938°W, depth 242 m, on a limestone rockwall, coll. L.E. Becking & E. Meesters, field nr. BON4/ BDR049 , 31 May 2013.

Description. Encrusting (1–2 cm thick) with 30–35 slightly elevated oscules scattered over the smooth surface. In situ size approximately 15 x 10 cm, of which 7 small fragments were collected the largest of which is 5 x 2.5 x 1 cm ( Figs. 2a,b ). Color green-grey alive, chocolate-brown in preservation. Consistency firm and crumbly.

Skeleton. A dense mass of diods and triods arranged around the aquiferous system. At the surface the skeleton is alveolar consisting of rounded meshes of approximately 50–60 µm diameter surrounded by a dense mass of small diods ( Fig. 2c ). Choanosome densely packed with bundles of diods mixed with triods and calthrops, the latter of which carry the tangential crust. There are some small subdermal cavities. In the overall spiculation diods dominate, but there is a relatively large proportion of large calthrops ( Fig. 2d ).

Spicules. Calthrops, diods, triods.

Calthrops ( Fig. 3a, b ) are abundant and large, 200– 457 – 700 µm in overall diameter of the cladome, with actines 110– 299 –500 x 15– 35 – 50 µm, usually slightly inequiactinal.

Diods centrotylote, some crooked in the middle, arbitrarily divisible in two size classes ( Fig. 3c, d ): smaller, generally angularly curved, 20– 36 –72 x 1.5– 2.65 – 3.5 µm, and larger, 75– 123 –170 x 3– 8 – 10 µm.

Triods ( Fig. 3e ) 15– 68 – 125 µm in overall diameter of the cladome, with conical actines 5– 35 –70 x 2.5– 4.5 – 10 µm, either equiactinal or with one relatively long actine.

Ecology and distribution. One specimen collected on carbonate rock wall in the upper dysphotic zone at Bonaire.

Etymology. Named after STINAPA (Sti chting Na tionale Pa rken) Bonaire, a non-governmental not-for-profit organization that manages and actively conserves the Bonaire National Marine Park.

Remarks. Of the twelve accepted species of Plakinastrella listed in Van Soest et al. 2014, only three species are recorded from the whole of the Central West Atlantic, including the Greater Caribbean, Carolinian and Brazilian waters. These are Plakinastrella onkodes Uliczka, 1929 , P. microspiculifera Moraes & Muricy, 2003 , and P. globularis Domingos et al., 2013 . Our new species differs from all three by the relatively giant calthrops: actines up to 500 x 50 µm against up to 152 x 26 µm in P. onkodes (cf. Zea 1987) only up to 45 x 9 µm in P. microspiculifera and 24–53 µm in P. globularis . The latter species is from approximately the same depth (90–170 m, off the northeast coast of Brazil).

Elsewhere, only Mediterranean P. copiosa Schulze, 1880 has rather similar large calthrops, up to 320 x 30–35 µm (measurements by Topsent 1895). This species also has ‘giant’ diods up to 600–700 x 30–33 µm, which sets it clearly apart from our new species. Its colour is indicated as white or pale yellow. Another species with the combination of giant calthrops (200–400 x 20–30 µm) and giant diods (800–1100 x 15–40 µm) is Philippine P. polysclera Lévi & Lévi, 1989 , but this has also giant triods with actines up to 900 x 50 µm. Its colour is described as rosy-ochraceous. Finally, P. trunculifera Topsent, 1927 has calthrops actines up to 190 x 23 µm and diods up to 455 x 15 µm, and thus differs clearly in these dimensions from our new species, while it is white-pale yellow in colour.

Figures

FIGURE 2. Plakinastrella stinapa n. sp., holotype RMNH Por. 9252, a. habit of holotype in situ on limestone rockwall W of Bonaire, b. preserved fragments, c. light microscope image of surface skeleton, d. light microscope overview of the spicule complement.

FIGURE 3. Plakinastrella stinapa n. sp., holotype RMNH Por. 9252, SEM images of the spicules, a. overview, b. calthrops, c. large diods, d. small diods, d1. enlarged small diod, e. triods, e1. enlarged triod.