Leucascus schleyeri, 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 : 73-76

Leucascus schleyeri sp.nov.

Figures 41a–g , 42a–h

? Clathrina reticulum ; Borojević 1967: 189, fig. 2 (not: Schmidt 1862).

Clathrina aff. reticulum ; Rudi et al. 2000: 1434.

Material examined. Holotype, ZMA Por. 15734, South Africa, Kwazulu Natal, Sodwana Bay, 27.55°S 32.6833°E, coral reef, depth 22–27m, scuba, coll. M. Schleyer, field nr. TASA53 -S52, year 2000, undated.

Description. Massive lobate cormus ( Fig. 41a ), consisting of densely and tightly anastomosed tubuli, with oscules on top of the lobes leading to atrial spaces. Color pink in situ. Preserved material consists of two fragments, each 2 x 2 x 1 cm of the much larger specimen, estimated to be 6 x 4 x 2 cm, most of which was used for natural products research. The preserved fragments are white or cream colored ( Fig. 41b ) and comprise several contracted lobes.

Aquiferous system. Asconoid, limited to the anastomosed tubuli.

Skeleton. In cross section ( Figs 41c–d ) the skeleton shows the dense arrangement of contracted tubuli of 0.1–0.2 mm in diameter surrounding shallow atria ( Fig. 41d ). The atrial walls are separated from the walls of the tubuli by their own layer of tri- and tetractines, as is visible in some parts of Figs 41c–d . There is a cortical surface layer ( Figs 41e–f ) recognizable by the presence of erect banana-shaped diactines, detailed also in Figs 15c–d . The walls of the tubuli are built by several layers of triactines and tetractines. The latter protrude with their apical actines into the tubule lumen ( Fig. 42a ). We noticed the presence of parasitic or commensal copepods in the cormus ( Fig. 42b ).

Spicules. ( Figs 42e–h ) Triactines and tetractines, the latter with spined apical actines.

Triactines ( Fig. 42e ) equiradiate and equiangular, with cylindroconical actines measuring 54– 74.6 – 90 x 4.5– 6.7 –8.5 µm.

Tetractines ( Figs 42f–g ) similar in shape and size to the triactines, occasionally somewhat sagittal, with thin straight apical actines provided with three rows of strong spines the position of which is matching the basal triradiate system ( Figs 42g ), actines of the basal triradiate system 63– 78 – 91 x 5 – 6.5 –8.5 µm, apical actines 31– 49 – 76 x 2 – 4.4 –7 µm.

Diactines, asymmetrical, curved, ‘banana’-shaped, often eroded (probably artefactual) and grooved, 48– 76 – 98 x 8 – 9.6 –12 µm.

Distribution and ecology. Natal coast of South Africa, deep reef.

Etymology. Named after Dr Michael Schleyer, Oceanographic Research Institute, Durban, South Africa, who collected the material, and in recognition of his important work on the marine ecology of South Africa.

Remarks. Although we do not have molecular sequence data for this specimen, the overall similarity of the present material with Leucascus , reviewed by Cavalcanti et al. (2003), makes it likely that the present new species is also a member of that genus. Our SEM cross sections ( Figs 41c–d ) show the characteristic structure of short atrial cavities surrounded by tightly anastomosed tubuli, with the whole cormus covered with a cortex of erect short diactines. Of the described species of Leucascus , only South Australian L. clavatus Dendy, 1892 possesses diactines, but these are much larger and thicker (350–850 x 99 –140 µm) than those of the new species, while also the tri- and tetractines are significantly larger (actines 70–160 x 9–19 µm).

Borojević (1967) reported Ascaltis reticulum ( Schmidt, 1862) (as Clathrina ) from South Africa, from both the Indian Ocean coast (‘Natal shore’) and from the Atlantic coast (False Bay). He gave a general description for these specimens, which fits our material except for the diactines, which measured 100–200 x 15–20 µm, well in excess of our diactines. No mention was made of spines on the apical actines of the tetractines. A. reticulum is originally described from the Mediterranean ( Schmidt, 1862). It is possible that at least the Natal specimens could be conspecific with our specimen rather than with A. reticulum . Klautau et al. (2016) redescribed Adriatic Ascaltis reticulum ( Schmidt, 1862) and provided molecular sequence data. The spicule types and sizes described by Klautau et al. conform rather closely to those cited above for our specimen, except for the diactines which were longer and thinner (60–142 x 4–6 µm) and not eroded. Of course, Ascaltis differs from Leucascus in lacking a lined atrial cavity ( Borojević et al. 2002a), and generally is less elaborate in shape and structure. Molecular sequence data of Ascaltis reticulum provided by Klautau et al. (2016), and downloaded from GenBank were found to group at a rather low bootstrap value with sequences of the Indonesian Leucascus flavus described by us previously (Van Soest & De Voogd, 2015) in our Calcinea phylogeny ( Fig. 2C ). This would confirm a close relationship of Ascaltis and Leucascus as postulated by Borojević et al. (2002a). Nevertheless, there are no molecular sequence data available for the type species of Ascaltis , A. lamarcki ( Haeckel, 1872) , so the true affiliation of Leucascus and Ascaltis remains uncertain.

Dendy’s (1913) Leucosolenia gardineri from the Western Indian Ocean on paper looks close to the present new species, the major obvious difference appearing to be the lack of banana-shaped diactines in L. gardineri . The species is currently assigned to Ascaltis .

Novel natural products, clathculins A and B, have been described from this specimen by Rudi et al. 2000.

Figures

FIGURE 2. Maximum-likelihood tree based on analysis of sequences of the partial 28S gene (C2–D2 region, comprising 442 sites) of Western Indian Ocean Calcinea newly generated by the Naturalis Biodiversity Center and sequences additionally obtained from GenBank, the Sponge Barcode Project and from Oliver Voigt (München) from the Red Sea, Indonesia, Australia, and a few sequences from other parts of the world, to demonstrate the affiliation of the compared species. Please note that Arturia sequences do not appear in the same clade, indicating Arturia is non-monophyletic. Numbers at the root of clades are bootstrap values of 1000 replicates. Since the high number of sequences were difficult to read in detail, we subdivided the present tree in three detailed sections 2A, 2B, and 2C.

FIGURE 15. Clathrina sinusarabica Klautau & Valentine, 2003, a, light microscopic view of part of the cormus and tubuli of RMNH Por. 10003 from Jeddah, b–d, SEM images of spicules, b, of Jeddah specimen RMNH Por. 10003, c, of Aqaba specimen ZMA Por. 13414, d, of Aqaba specimen ZMA Por. 13476.

FIGURE 41. Leucascus schleyeri sp.nov., holotype ZMA Por. 15734, a, habitus in situ on the deep reef of Sodwana Bay, Kwazulu Natal, South Africa (photo M. Schleyer), b, preserved fragments of holotype (scale bar = 1 cm), c, SEM image of cross section of cormus showing dense mass of tubuli, d, detail of c showing shallow pseudoatrium, e, SEM image of overview of surface, f, detail of e showing erect diactines.

FIGURE 42. Leucascus schleyeri sp.nov., holotype ZMA Por. 15734, a, SEM image of wall of tubulus with protruding apical actines of tetractines, b, SEM image of parasitic or commensal copepods lodged in the cormus, c, SEM image of perpendicular section of the upper surface showing crowded ‘banana’-shaped erect diactines, d, light microscopic image of the same, e–h, SEM images of spicules, e, triactine, f, tetractines, g, details of apical actines of tetractines, h, ‘banana’-shaped diactines from the upper surface.