Leucascus schleyeri Van & De 2018, sp.nov.
Creators: name: Van, Rob W. M.
name: De, Nicole J.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Calcarea
Clathrinida
Leucascidae
Leucascus
Leucascus schleyeri

description: 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.
description: Published as part of Van, Rob W. M. & De, Nicole J., 2018, Calcareous sponges of the Western Indian Ocean and Red Sea, pp. 1-160 in Zootaxa 4426 (1) on pages 73-76, DOI: 10.11646/zootaxa.4426.1.1, http://zenodo.org/record/1271239