Placospongia ruetzleri, Van, Rob W. M., 2017

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225 : 173

Placospongia ruetzleri sp. nov.

Figures 108 a–g

Placospongia carinata sensu Little 1963: 56 , figs 25, 27; Hechtel 1965: 62 (in part, not specimens with spherasters);? Hechtel 1976: 241;? Coelho & Mello-Leitão 1978: pages unnumbered, figs 1–2; Pulitzer-Finali 1986: 100; Rua et al. 2006: 197; Muricy et al. 2011: 67 (Not: Geodia carinata Bowerbank, 1858 ).

Placospongia sp. 1 sensu Van Soest 2009: 11.

Material examined. Holotype RMNH Por. 9872, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station F46, 6.312°N 56.57°W, depth 25–29 m, bottom sand, 7 May 1966 .

Paratypes RMNH Por. 9951, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station F46, 6.312°N 56.57°W, depth 26–29 m, bottom sand, 7 May 1966 ; RMNH Por. 9871, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station F45, 6.4417°N 56.5467°W, depth 34 m, Van Veen grab, 7 May 1966 .

Description. ( Fig. 108 a) Thick crusts with surface divided into polygonal plates separated by pore grooves. Live color of specimens photographed on-deck by the CREOCEAN expedition in French Guyanan waters is redbrown, similar but slightly dulled in alcohol. No visible openings (the oscules and pores in the grooves are invisible due to the closure of the grooves). Size of holotype 5.5 x 4 x 3.5 cm, but the thickness in reality is about 4–5 mm, as it encloses a lump of shell debris. The paratypes are flat encrustations of 3–6 mm thickness. Consistency stony.

Skeleton. The surface has a thin veneer of acanthomicrorhabds overlying a 1.5 mm thick crust of selenasters, carried by subectosomal bundles of tylostyles of 300–500 µm in diameter. The choanosomal region is notably less spiculous, with spaces of 0.5–1 mm of tissue with only microscleres (acanthomicrorhabds and spirasters/ amphiasters) between the bundles of tylostyles. At the undersurface there is a further layer of selenasters and acanthomicrorhabds.

Spicules. ( Figs 108 b–f) Tylostyles, selenasters, spirasters, acanthomicrorhabds.

Tylostyles with prominent tyles and bluntly rounded opposite ends, straight and evenly thick along most of the shaft, gradually tapering until the rounded end, in two slightly overlapping size classes, (1) larger ( Figs 108 b,b1) 618– 856 – 1158 x 11 – 14.6 –19 µm, and (2) smaller ( Figs 108 c,c1) 324– 395 –479 x 6 – 8.7 –11 µm.

Selenasters ( Fig. 108 d) oval in shape with prominent hilus of 10–13 µm diameter, size (height x diameter) 66– 76.2 –82 x 51 – 59.7 –66 µm; juvenile stages ( Fig. 108 e) common, 34– 40.3 – 48 x 15 – 21.1 –27 µm.

Spirasters ( Figs 108 f), quite variable and irregular, the shaft with one or rarely two spiral turns; with rays provided with shorter and longer secondary rays and spines, with the longer rays concentrated at both ends and on the upper curve, with few spines and protrusions in the center region and on the lower curve; overall length also variable, 16– 21.7 –26 µm, thickness of the shaft where free of spines, 2–4 µm.

Acanthomicrorhabds ( Figs 108 g), variable in length and thickness, usually with one or one-and-a-half spiral turn, occasional with two turns, initial stage rough but not spined, size 7– 11.4 – 14 x 1 – 1.4 –2 µm.

Distribution and ecology. Guyana shelf, sandy bottom at 25–34 m; CREOCEAN specimens from French Guyana were from 83 m depth. Elsewhere, Florida, Jamaica, Grenada, Colombia, NE Brazil (the Brazilian records remain uncertain due to insufficient information), depth range 1–34 m, so the entire range is 1– 83 m.

Etymology. Named after Dr Klaus Rützler (Smithsonian Institution, Washington), to acknowledge his efforts in placospongiid taxonomy and for his important contributions to sponge biology in general.

Remarks. This species was already reviewed and described in Van Soest (2009) as Placospongia sp. 1. The Pacific holotype of P. carinata ( Bowerbank, 1858) and additional regional specimens were (re-)described by Becking (2013). The Central West Atlantic specimens previously assigned by various authors to P. carinata closely resemble the Pacific P. carinata , but as Van Soest (2009) pointed out there are several consistent differences which along with the geographic separation justify recognition at the species level. The principal difference is the shape of the spirasters/amphiasters, which is much more distinctly amphiaster-like with long rays at both upper and lower ends of the shaft in P. carinata , whereas these spicules are pronouncedly spiraster-like in the new Central West Atlantic species because rays tend to be lengthy only at the upper convex side of the arched microsclere. Less clear, but consistent differences are in the sizes of these spirasters/amphiasters (larger in P. carinata ), the megascleres (shorter in P. carinata ), and the selenasters (larger in P. carinata ).

All other well-established Central West Atlantic Placospongia species ( P. caribica Rützler, Piantoni, Van Soest & Díaz, 2014 , P. cristata Boury-Esnault, 1973 , and P. intermedia Sollas, 1888 ) possess ‘golfball’-shaped spherasters lacking in the present species.

Figures

FIGURE 108. Placospongia ruetzleri sp. nov., a, habitus of holotype 9872 (scale bar = 1 cm), b – g, SEM images of the spicules, b, large tylostyle, b 1, details of b, c, small tylostyle, c 1, details of c, d, selenaster, e, juvenile selenaster, f, spirasters, g, acanthomicrorhabds.