Vosmaeropsis glebula, Van & De, 2018

Van, Rob W. M. & De, Nicole J., 2018, Calcareous sponges of the Western Indian Ocean and Red Sea, Zootaxa 4426 (1), pp. 1-160 : 128-130

Vosmaeropsis glebula sp.nov.

Figs 79a–g

Material examined. Holotype, ZMA Por. 10608, Seychelles, La Digue Island , S coast, 4.3833°S 55.8333°E, depth 2 m, reef, snorkeling, coll. R.W.M. van Soest, field nr . NIOP-E stat. 735/ 28, 23 December 1992.

Paratypes, ZMA Por. 10553, Seychelles, Aride Island, S coast, 4.2167°S 55.6667°E, snorkeling, coll. J.C. den Hartog, field nr . NIOP-E stat. 711/ 12, 18 December 1992; ZMA Por. 10637, Seychelles, Amirantes , St. François Atoll, Île Bijoutier, depth 3 m, reef, scuba, coll. R.W.M. van Soest, field nr . NIOP-E stat. 792/ 20, 6 January 1993.

Description. Small lobes and short thick-walled tubes ( Fig. 79a ), occurring singly or in coalescent groups. The holotype consists of five such lobes, which were originally grouped together. Each lobe or tube carries a terminal oscule. Color in situ yellow-brown, in preservation they are similarly light brown. Size 1–2 cm in height, 0.5–1 cm in diameter, oscules about 2 mm in diameter, flush, without rim or fringe. Consistency soft.

Aquiferous system. Leuconoid.

Skeleton. ( Figs 79b–c ) In our SEM cross section ( Fig. 79b ), which is admittedly rather confused, from surface to atrium there is a cortical skeleton of smaller sagittal and larger regular triactines ( Fig. 79c ), supported by subcortical pseudosagittal triactines replaced by giant triactines in the main skeleton. In the atrial region there are larger triactines rather similar to the cortical triactines but supported by smaller, more or less regular triactines.

Spicules. ( Figs 79d–h ) Triactines only, tentatively divisible into cortical triactines, giant triactines, pseudosagittal triactines, subatrial triactines and atrial triactines.

Cortical triactines ( Fig. 79d ), regular, usually with straight actines, intermediate in size, actines 76– 168 –258 x 8 – 15.1 –31 µm.

Pseudosagittal triactines ( Fig. 79f ), longest actines 270– 474 –662 x 18 – 36.7 –47 µm, middle sized actines 167– 261 –330 x 17 – 32.1 –40 µm, shortest (=unpaired) actines 81– 129 –292 x 18 – 32.8 –41 µm.

Giant or large triactines ( Fig. 79e ) of the main skeleton, tending to be more or less equiangular and equiradiate, 302– 567 –779 x 32 – 57.4 –78 µm.

Subatrial and atrial triactines ( Figs 79g ), slightly sagittal, intermediate and smaller triactines, often with incurved paired actines; unpaired actines 93– 141 –233 x 15 – 20.3 –26 µm, paired actines 111– 195 –271 x 15 – 19.6 –24 µm.

Distribution and ecology. Known only from several localities in the Seychelles, reefs, shallow water.

Etymology. Glebula (L.) meaning small lump, referring to the habitus.

Remarks. The new species is assigned to Vosmaeropsis on account of the confused choanosomal skeleton in combination with pseudosagittal triactines. So far, no Vosmaeropsis species are known from the Western Indian Ocean (cf. Cavalcanti et al. 2015; Van Soest et al. 2018). The new species differs from most Indo-West Pacific Vosmaeropsis species, including e.g. V. grisea Tanita, 1939 as described by us from Indonesia (cf. Van Soest & De Voogd 2015), in the lack of (giant) diactines and tetractines. Only two species in that wide area share the lack of diactines and tetractines with our new species. In Philippine deeper water occurs V. connexiva ( Poléjaeff, 1883), which differs from our specimens in the apparent lack of small cortical and atrial triactines, while the pseudosagittal triactines are smaller than those of the new species, with longest actines not exceeding 400 x 20–25 µm (in our specimens up to 662 x 47 µm). The habit of the species is not clear as Poléjaeff only had a few fragments. New Caledonian V. hozawai Borojević & Klautau, 2000 is a larger (5 cm) dark brown, sac-shaped sponge from 20–25 m depth. It differs especially in the much larger size of the giant triactines, which are up to 1500 x 100 µm (ours 779 x 78 µm); likewise the regular cortical and atrial triactines are larger, up to 420 x 17 µm (ours up to 271 x 26 µm). Despite the lack of illustrations for these two species, the differences are here considered sufficiently great to judge them to be different from our new species. In the area considered here there are no reports of additional Vosmaeropsis species.

Unfortunately, our attempt to obtain a partial 28S sequence of the type material failed.

Figures

FIGURE 79. Vosmaeropsis glebula sp.nov., holotype ZMA Por. 10608 from the Seychelles, a, preserved habitus (scale bar = 1 cm), b–c, SEM images of skeleton, b, cross section through the wall, c, view of the surface skeleton, d–g, SEM images of the spicules, d, cortical sagittal triactine, e, subcortical pseudosagittal triactines, f, giant and large choanosomal triactines, g, subatrial and atrial triactines.