Pyloderma tropicale Van, 2017, sp. nov.

Pyloderma tropicale sp. nov.

Figures 86 a–d

Material examined. Holotype RMNH Por. 10513, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station F46, 6.312°N 56.57°W, depth 25–29 m, bottom sand, 7 May 1966.

Description. The holotype (Fig. 86 a) is fragmented, but assumed to have been originally a single specimen of 10 x 5 cm in lateral expansion, less than 1 cm thick. The fragments are bladder-like with an irregular undulating semitransparent surface sheet with many tiny fistules. The interior is cavernous, with few skeletal structures. Color beige-brown in alcohol. Consistency soft but elastic.

Skeleton. (Fig. 86 b) Loose choanosomal tracts of 100–150 µm diameter rise up from the substratum and fan out to carry the surface membrane.

Spicules. (Figs 86 c–d) Oxeas only.

Oxeas, straight, equidiametrical, with lance-shaped, slightly swollen sharply pointed apices; in shape and position in the skeleton there appear to be two (largely) overlapping categories, (1) shorter and thicker (Figs 86 c,c1), 134– 166 –189 x 6 – 7.3 –9 µm, and (2) longer and thinner (Figs 86 d,d1), 156– 183 –213 x 2.5– 3.4 –4.5 µm.

Distribution and ecology. Guyana Shelf, on sandy bottom at 25–29 m depth.

Etymology. The name reflects the unusual occurrence of a Pyloderma species in tropical waters.

Remarks. No other sponges with these peculiar lance-shaped oxeas are known from the Central West Atlantic. Assignment of this unusual species to the genus Pyloderma is tentative, but presently the best fit. It can only be tested by comparison of additional material and/or molecular analyses to resolve this systematic hypothesis. The type species of Pyloderma, Southern Ocean Halichondria latrunculioides Ridley & Dendy, 1886 is pear-shaped and has much larger oxeas (up to 1200 µm), but the form of the latter is also lance-shaped like in the present species (cf. Van Soest 2002a). The only other species of Pyloderma, the New Zealand P. demonstrans Dendy, 1924 has chelae and sigmas, for which reason the (presently unaccepted) genus Manawa Bergquist & Fromont, 1988 was erected. If the present species indeed belongs to Pyloderma, then resurrection of Manawa might be considered.