Clathria (Thalysias) curacaoensis Arndt 1927

Clathria (Thalysias) curacaoensis (Arndt, 1927)

Figures 93 a–k

Clathria copiosa var. curacaoensis Arndt, 1927: 148, pl. I fig. 3, text-fig. 9.

Aulospongus schoenus De Laubenfels, 1936: 100, pl. 13 fig. 4.

Rhaphidophlus schoenus; Van Soest 1984: 112, p. VIII figs1–4, text-fig. 44.

Clathria (Thalysias) curacaoensis; Zea et al. 2014: 407, figs 4–6, pl. I figs C–E, with further synonyms.

Material examined. RMNH Por. 9944, Guyana, ‘Luymes’ Guyana Shelf Expedition, station 63, 7.5833°N 57.0667°W, depth 71 m, sandy bottom, 31 August 1970.

Description. (Fig. 93 a) Encrusting on calcareous debris, with optically smooth, but microconulose surface. Color in alcohol red-brown. No apparent oscules. Lateral size about 3 x 1.5 cm, thickness 0.5–2 mm. Consistency soft.

Skeleton. (Fig. 93 b) The choanosomal skeleton consists of spongin-enforced plumose spicule tracts, 50–100 µm in diameter, cored by 4–10 styles. Tracts sparingly echinated by acanthostyles. Near the surface the tracts fan out to form bouquets consting of various sizes of subtylostyles, the larger supporting the smaller in the bouquets. Microscleres spread throughout the skeleton.

Spicules. (Figs 93 c–k) Styles, subtylostyles, peculiar T-shaped subtylostyles, acanthostyles, palmate isochelae, toxas.

Styles (Figs 93 c,c1), curved, smooth, but occasionally with very faint microspines on the head, in a wide size range, 198– 369 –497 x 7.5– 12.3 –17 µm.

Subtylostyles (Figs 93 d–f), straight, smooth, with faintly swollen heads consistently provided with a few spines, occasionally heavily spined, in three arbitrarily distinguished size categories (may be slightly overlapping), (1) largest (Figs 93 d,d1), 291– 378 –462 x 4 – 6.1 –9 µm, (2) middle-sized (Figs 93 e,e1), 135– 206 –286 x 3 – 3.3 –4 µm, and (3) smallest (Figs 93 f,f1), 98– 112 –141 x 1.5– 1.7 –2 µm.

T-shaped tylostyles (Figs 93 g,g1–g3), probably abnormally developed versions of the smallest subtylostyles, but the frequency is high enough (about 5%) to consider them worth describing and imaging; the heads are swollen to the extent that they appear to have multiple heads, each swelling with spines of its own; size similar to the smallest category of subtylostyles, 90– 99 –114 x 1.5– 2.2 –3 µm.

Acanthostyles (Fig. 93 h), short, stubby, with the part of the shaft just below the spined head characteristically free or almost free of spines, 39– 54 – 73 x 3.5– 5.6 –6.5 µm.

Palmate isochelae (Figs 93 i–j) in two size and shape categories, (1) larger (fig. 93i), normal shaped, with short alae and long free shaft, 12– 13.3 –15.5 µm, and (2) tiny twisted chelae (Figs 93 j,j1), 4– 5.7 –6.5 µm.

Toxas (Fig. 93 k), thin, shallow-curved, with straight legs, in a large size range 62– 121 –179 µm.

Distribution and ecology. Guyana shelf, throughout the Caribbean, Carolina region, encrusting various hard objects, at 3–71 m depth (previously to 35 m).

Remarks. The specimen described above keys out as C. (T.) curacaoensis in Zea et al. ’s (2014) key and also conforms in most aspects to Arndt’s holotype and Zea’s specimens and his review. The only noteworthy difference is the presence in the Guyana shelf specimen of three-four categories of subtylostyles, including a considerable number of abnormally developed spicules of the smallest category. For the time being, these are considered as variability of a widespread species. The present specimen extends the depth occurrence of this shallow-water species from 35 to 71 m.