Fig. 6
Named after the type locality, Ilheu de Cima.
Holotype
ZMA Por. 07282, Cape Verde Islands, SW of Ilheu Rombos, SE of Ilheu de Cima, depth 165 m, hard bottom with yellow calcareous sand, coll. R. W.M. Van Soest, CANCAP 7 Expedition stat. 030/05, 14.95°N 24.65°W, Van Veen grab, 23 Aug. 1986.
Thinly encrusting on a large volcanic stone ( Fig. 6A, arrow), alongside a specimen of Aplysilla Schulze, 1878. Size of crust 3.5 x 2 cm, thickness 1-2 mm. Colour: yellow alive, beige in alcohol. Surface optically smooth. Consistency soft.
SKELETON. ( Fig. 6B) Plumose, with strongly developed spicule bundles traversing the sponge at right angles to the surface, where they fan out. Few if any connecting spicules. No special ectosomal skeleton. There is a ‘groundmass’ of microscleres crowding the space between the spicule bundles and adhering to it, mostly consisting of sigmas and small isochelae. Scattered larger chelae, rather rare, mostly occurring at the surface.
SPICULES. ( Fig. 6 C-E) Styles, sigmas, palmate isochelae.
STYLES. ( Fig. 6C, C 1) Long and thin, straight or slightly curved, 396- 431.4 -461 x 5- 6.4- 8 µm.
SIGMAS. ( Fig. 6D) In two distinct non-overlapping size categories, both thin and strongly curved: (I) 76- 85.8 - 96 µm ( Fig. 6D 1), and (II) 36- 45.4 - 56 µm ( Fig. 6D 2).
PALMATE ISOCHELAE. ( Fig. 6E) In two distinct, non-overlapping size categories, the larger (I) ‘normal’ in shape ( Fig. 6E 1), 56- 69.4 - 84 µm, the smaller (II) with incurved median alae ( Fig. 6E 2), 14- 16.9 - 21 µm.
Only known from the type locality S of Ilheu de Cima, Cape Verde Islands ( Fig. 1, loc. 5), on volcanic bottom with yellow sand, at 165 m depth.
The new species appears to be a member of a group of morphologically similar North Atlantic deep-water species (see Table 1), sharing the encrusting habit, the size and shape of megascleres and two categories of both sigmas and chelae. Probably closest is Esperiopsis flagellum Lundbeck, 1905 from off SE Iceland. Clear differences exist in the shape of one of the sigma categories, as these of E. flagellum are ‘flagellate’ (excessively incurved). The sigmas are also larger in size, up to 250 µm in E. flagellum, whereas they are up to 400 µm in the similar species E. macrosigma Stephens, 1916 from waters west of Ireland. E. praedita Topsent, 1890 from the Azores is also close, but the larger chelae category is smaller than in our new species, and the sigmas can be as large as 200 µm. A less similar sponge is E. decora Topsent, 1904 from the Azores, sharing the overall spiculation, but having even larger (flagellate) sigmas, and in addition possessing trichodragmas and three instead of two size categories of chelae. Other Esperiopsis species described from the North Atlantic appear more distant: E. incognita Stephens, 1916 from Irish waters has smaller chelae and larger sigmas. E. strongylata (Alander, 1942) from the Skagerrak and E. strongylophora Vacelet, 1969 from the Western Mediterranean have strongylote megascleres instead of styles. The two remaining, more elaborately shaped, North East Atlantic Esperiopsis species also show differences in spicule sizes and categories: variably massive or ramose E. polymorpha Topsent, 1890 from the Azores has smaller chelae in a single category and smaller sigmas. Massive-erect or leafshaped E. villosa (Carter, 1874) has the size of the largest sigmas and chelae clearly in excess of those of our new species.
Esperiopsis schmidti Arnesen, 1903 from Norwegian waters and Esperiopsis glomeris Topsent, 1904 have been assigned to the myxilline genus Echinostylinos Topsent, 1927 by Van Soest & Hajdu (2002a) on account of their possession of tridentate isochelae. Esperiopsis typichela Lundbeck, 1905 and Esperiopsis pedicellata Lundbeck, 1905 have been transferred to Amphilectus by Van Soest et al. (2012) as they do not possess sigmas. Esperiopsis lesliei Uriz, 1988 and Esperiopsis rugosus sensu Uriz (1988) both from Namibia, likewise do not have sigmas and belong to Amphilectus.