Erylus rhabdocoronatus, Van, Rob W. M., 2017

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225 : 88-90

Erylus rhabdocoronatus sp. nov.

Figures 55 a–g

Material examined. Holotype RMNH Por 9339, French Guyana, ‘Luymes’ Guyana Shelf Expedition, station 14, 6.7333°N 52.75°W, depth 76 m, bottom muddy calcareous sand, 26 August 1970 .

Examined for comparison. Slide of the holotype of Erylus alleni De Laubenfels, 1934 , USNM 22268 , from Puerto Rico, 68–171 m.

Description. A fragment of a finger-shaped sponge ( Fig 55 a), 2.5 cm high and 8 mm in diameter. Color in alcohol beige, both inside and outside. Surface optically smooth, but microhispid due to being overgrown by a thinly encrusting Spirastrella (see below); no apparent openings. Consistency firm, but fragile.

Skeleton. The usual surface skeleton is present consisting of a layer of partially overlapping aspidasters covered by a dense mass of microrhabds and carried by the cladomes of subcortical orthotriaenes. Choanosomal skeleton a largely confused mass of oxeas and a few triaenes, with bundles of oxeas traversing the choanosome.

Spicules. ( Figs 55 b–g) Oxeas, plagiotriaenes, microrhabds, aspidasters, two categories of oxyasters.

Oxeas ( Figs 55 b,b1), fusiform, curved, with sharp points, 261– 513 –648 x 14 – 21.1 –29 µm.

Ortho/plagiotriaenes ( Fig. 55 c), short-shafted; rhabdomes 204– 309 –378 x 9 – 15.3 –24 µm, cladomes 305– 371 –450 µm; cladi 163– 206 –224 x 9 – 11.6 –21 µm.

Microrhabds ( Figs 55 d,d1), curved, centrotylote, all are provided with rounded ends bearing a crown of conical spines ( Fig. 55 d1); sizes 36– 48 – 57 x 2.5– 4.1 –6 µm.

Aspidasters ( Figs 55 e,e1), oval, thin, provided with rather spaced out rosettes, 138– 148 –159 x 89 – 94 –102 µm.

Large oxyasters ( Figs 55 f), with almost smooth rays, only occasional spines, variable diameters, 19– 52 –60 µm, ray number 3–6.

Small oxyasters ( Fig. 55 g), with much more rays, but also with few spines; diameters 12– 14.6 –21 µm, ray number 9–14.

Distribution and ecology. Guyana Shelf, sandy bottom at 76 m depth.

Etymology. The name reflects the crown of blunt spines on the apices of all the microrhabds.

Remarks. The new species differs from the closest species, E. alleni De Laubenfels (1934) in the following features—based on a comparison with a slide made from the holotype USNM 22268 and spicule measurements—(1) the aspidasters are larger (138–159 x 89 –102 µm in the present species vs. 70–114 x 30–81 µm in E. alleni (curiously De Laubenfels gives only 70 x 35 µm); (2) the microrhabds do not have the crown of spines and are on average shorter; (3) oxeas are approximately half as thick in E. alleni ; (4) the euaster sizes given by De Laubenfels are half the diameter (30 µm and 7 µm) of those of the new species, but re-measurement yielded sizes on average similar in both species. Perhaps De Laubenfels gave measurements of the rays. However, the shape of the rays of the larger euasters differs clearly in E. alleni by being thinner and curved or slightly flexuous, not rigid like in E. rhabdocoronatus sp. nov.

Mothes et al. (1999) redescribed E. alleni and also assigned several specimens along the Brazilian coast to that species. Spicules of one of the specimens were depicted in their fig. 4 and these images appear close to those of E. rhabdocoronatus sp. nov., especially the euasters, but there are no spines on the ends of the microrhabds, and the shape of the aspidaster is subtly broader. The larger oxyasters in Mothes et al. ’s E. alleni are dissimilar to those seen in the slide of the holotype of E. alleni examined here.

Van Soest & Stentoft (1988) (p. 17) reported Erylus transiens from 100 m off Barbados, which does not conform to Weltner’s (1882) description of that species (perhaps it is E. corneus Boury-Esnault, 1973 ). These authors suggested E. transiens sensu Sollas (1888) and E. alleni were synonyms. According to Mothes et al. (1999: 375), followed by Muricy et al. (2011: 44), the two species differ in the possession of one ( E. transiens ) vs. two categories of oxyasters.

The decoration of the microrhabds with crowns of spines is intermediate between entirely smooth microrhabds and those that are spined all over such as in Erylus granularis Topsent, 1904 from the Azores and Erylus soesti Mothes & Lerner, 2001 from Brazil.

Figures

FIGURE 55. Erylus rhabdocoronatus sp. nov., a, habitus of holotype RMNH Por. 9339 (scale bar = 1 cm), b – g, SEM images of spicules, b, oxea, b 1, details of b, c, orthotriaene, d, microrhabd, d 1, enlarged microrhabd to show crowns of spines on the apices, e, aspidaster, e 1, detail of surface of aspidaster, f, large oxyasters, g, small oxyaster.