Sponges of the Guyana Shelf Author Van, Rob W. M. text Zootaxa 2017 1 1 225 journal article 37320 10.5281/zenodo.272951 e2c88f4c-3ac2-45f9-95e4-99b75561a081 1175-5326 272951 6D68A019-6F63-4AA4-A8B3-92D351F1F69B Mycale (Mycale) arenaria Hajdu & Desqueyroux-Faúndez, 1994 Figures 97 a–d, 98a–g Mycale fusca ; Solé-Cava et al. 1981 : 132 (Not: Esperella fusca Ridley & Dendy, 1886 ). Mycale arenosa Hajdu & Boury-Esnault, 1991 : 506 , figs 1–11 (Not: Mycale parasitica var. arenosa Hentschel, 1911 ). Mycale arenaria Hajdu & Desqueyroux-Faúndez, 1994 : 568 (Not: Moraes 2011: 146, no sigmas, surface skeleton is characteristic for subgenus Aegogropila ). Material examined. RMNH Por. 9994, Suriname , ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station F40, 7.0033°N 56.4417°W , depth 59 m , bottom sand, 6 May 1966 . Description. Irregularly massive sponge ( Fig. 97 a), encrusting and consolidating shell debris on soft bottom substratum. Size 4 x 4.5 x 2 cm. Surface smooth but irregularly grooved and lobate. Several oscular openings are present, flush with the surface, 2–4 mm in diameter. Consistency soft, cavernous, but resilient. Skeleton. ( Figs 97 b–d) The surface skeleton is a tangential layer of single intercrossing megascleres ( Fig. 97 b). Rosettes of the largest anisochela category ( Fig. 97 b) are common, approximately 150 µm in diameter, consisting of 20+ spicules. The surface membrane in between the megascleres is charged with with scattered sigmas and anisochelae ( Fig. 97 c), and very numerous trichodragmas and single raphides ( Fig. 97 d). The choanosomal skeleton consists of strong, plumose bundles of megascleres, which fan out in the subectosomal region carrying the surface skeleton. Megasclere bundles at the base approximately 1 mm in diameter, thinning out towards the surface where they comprise 3–7 spicules in cross section. Spicules. ( Figs 98 a–g) Styles, anisochelae, sigmas, trichodragmas. Styles ( Figs 98 a,a1), mycalostyles, fusiform, with faint constriction beneath the rounded heads, the opposite end sharply pointed, 468– 620 –744 x 12 – 15.4 –20 µm. Anisochelae I ( Fig. 98 b), robust, with short alae, 50– 55.9 –63 µm. Anisochelae III ( Fig. 98 c), spurred, with upper alae long, in a large size range, possibly divisible in a larger and a smaller size category, overall 16– 19.4 –24 µm. FIGURE 97. Mycale (Mycale) arenaria Hajdu & Desqueyroux-Faúndez, 1994 , a, habitus of RMNH Por. 9994 (scale bar = 1 cm), b–d, light microscopic images of the ectosomal skeleton, b, overview of showing subgenus Mycale skeleton and rosettes of anisochelae, c, two size categories of sigmas, d, two size categories of trichodragmas. Sigmas, thin, with slightly incurved apices, in two distinct size categories, (1) larger ( Fig. 98 d), very common, 32– 40.4 –53 µm, and (2) smaller ( Fig. 98 e), less common, 12– 13.2 –15 µm. Raphides in trichodragmas, extremely common, in two size categories, (1) larger ( Fig. 98 f), 61– 74.5 – 93 x 11 – 12.4 –15 µm (individual raphides ( Fig. 98 f1) less than 0.5 µm thick), and (2) smaller ( Fig. 98 g), 17– 26.1 – 33 x 9 – 10.8 –12 µm. Distribution and ecology. Guyana Shelf, SE Brazil , soft substratum, 3– 59 m . Remarks. The similarity to the Brazilian type material extensively described by Hajdu & Boury-Esnault (1991) and Hajdu & Desqueyrouz-Faúndez (1994) is convincing. However, there are a few differences: the type apparently has two categories of megascleres, which I cannot confirm from the present specimen; nevertheless the overall sizes given for the type are the same as for the present specimen. Hajdu & Boury-Esnault do not report the occurrence of two size categories of sigmas, but since these were fairly rare and very thin, it is possible that either category was overlooked. The presence of a rare anisochela II category of 40 µm is reported for the type , while in the present specimen there is at most a possible additional size category of anisochelae III of about 23–24 µm, which seems different from most other anisochelae by having wider alae. Finally, there is a distinct division into larger and smaller trichodragmas in the present specimen, not reported for the type material. In view of the considerable overall similarity of the present material and Hajdu & Boury-Esnault’s material, I consider them both the same species for the time being. Moraes’ (2011) record of this species is suspect as he did not mention sigmas and figured an Aegogropila surface skeleton. A closely related species is Mycale (Mycale) alagona Cedro, Hajdu & Correia, 2011 from SE Brazil . It shows the same general similarity with my specimen as with the type of M. (M.) arenaria (curved, short alae in anisochela I, dense aggregation of trichodragmas). Differences are three instead of two anisochelae categories and three size categories of sigmas.