Hymedesmia (Stylopus) alcoladoi Van, 2017, sp. nov.

Hymedesmia (Stylopus) alcoladoi sp. nov.

Figures 87 a–d

Material examined. Holotype RMNH Por. 9956, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station G7, 7.28°N 56.7933°W, depth 64 m, bottom sand, 7 May 1966.

Description. Thinly encrusting on a dead oyster shell. Color in alcohol brown. Thickness less than 1 mm.

Skeleton. Hymedesmioid (Fig. 87 a), with long acanthostyles and short acanthostyles erect on the substratum, heads embedded in a basal spongin plate. Choanosome and surface skeleton composed of scattered tornotes.

Spicules. (Figs 87 b–d) Acanthostyles, tornotes.

Acanthostyles, in two size categories, both with heavily spined heads, (1) larger (Figs 87 b,b1) with spination gradually diminishing towards the pointed end, 135– 176 –213 x 9 – 12.2 –17 µm, and (2) smaller (Fig. 87 c) spined heavily all over, not infrequently provided with bifid pointed ends 62– 79 –121 x 6.5– 7.2 –9 µm.

Tornotes (Figs 87 d,d1), smooth, mucronate, slightly swollen pointed apices, almost symmetrical, but one end slightly thinner than the opposite end, 151– 179 –222 x 2 – 2.4 –4 µm.

Distribution and ecology. Guyana Shelf, on shells at 64 m depth.

Etymology. Named after Dr. Pedro M. Alcolado (Instituto de Oceanología, Havana, Cuba) in recognition of his lifelong dedication to ecology and taxonomy of the Cuban sponge fauna.

Remarks. No previous records of Hymedesmia (Stylopus) are known from the Central West Atlantic. Recently, a Phorbas species without chelae was described, P. aurantiacus Rützler, Piantoni, Van Soest & Díaz, 2014. Theoretically, this could be considered close or conspecific as a more mature form of the present species. However, P. aurantiacus is clearly different in possessing styliform tornotes and three separate categories of acanthostyles. Moreover, both tornotes and acanthostyles reach much higher lengths (tornotes up to 590 x 10 µm, large acanthostyles up to 410 x 21 µm) than in the present material. This makes it quite unlikely that the two are conspecific.