Figures 113 a –b
Rhaphisia ambrosia De Laubenfels, 1936: 135.
Axinyssa ambrosia; Díaz et al. 1993: 289, figs 5, 10; Zea et al. 2013: 495, figs 1, 3A –C.
Material examined. RMNH Por. 9331, Guyana, ‘Luymes’ Guyana Shelf Expedition, station 65, 7.55°N 57.0833°W, depth 63 m, sandy bottom, 31 August 1970; RMNH Por. 9999, 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. Three lobate-digitate fragments ( Fig. 113 a), presumably the upper parts of sponges partially buried in the sand, and two parallel developed, elongate cylindrical specimens ( Fig. 113 a1). Size of digitate fragments 5–8 cm high, 2–4 cm in diameter, of cylindrical specimens 20 cm long, 2.5 cm in diameter. Color (alcohol) pale orange-beige. Surface irregular, but optically smooth, somewhat ridged and grooved. No apparent oscules. Consistency firm to hard.
Skeleton. No ectosomal specialization. The choanosomal skeleton is confused but shows arrangement of the spicules in tracts directed towards the surface.
Spicules. Oxeas only.
Oxeas ( Figs 113 b,b1) fusiform, sharply pointed, lightly curved, in a large size range, but not divisible in size categories, 618– 784 –954 x 16 – 25.2 –34 µm.
Distribution and ecology. Guyana Shelf, Florida, Curaçao, Jamaica, Colombia, reefs and sand, at 18–85 m depth (Gyana Shelf 34–65 m).
Remarks. The present specimens conform to the description of Axinyssa ambrosia as given by Díaz et al. (1993), who also assigned Dictyonella yumae Pulitzer-Finali, 1986 as a junior synonym. Subsequently, Zea et al. 2013 revised both species and concluded that there are small differences between the two and that they are distinct species. In their analysis they restricted the spicule sizes of Axinyssa ambrosia to 490–941 x 4.8–23.8 µm. The Guyana shelf material has slight larger and thicker oxeas (up to 954 x 34 µm), but these fall short of the sizes quoted by Zea et al. 2013 for Axinyssa yumae (up to 1121 x 37.4 µm). Although there are a few fusiform styles among the spicules of the present specimens, they are infrequent. In conclusion, the identity of the Guyana material is most likely to be A. ambrosia and not A. yumae.