Leucetta sulcata, 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 : 85

Leucetta sulcata sp.nov.

Figs 49a–d , 50a–d

Material examined. Holotype, RMNH Por. 11639, Mauritius, Rodrigues, Mourouk Ebony, Castel Rock , 19.76203°S 63.46273°E, depth 10 m, scuba, coll. N.J. de Voogd, field nr. ROG042, 17 October 2016.

Paratypes, RMNH Por. 11643, Mauritius, Rodrigues, Mourouk Ebony, Castel Rock , 19.76203°S 63.46273°E, depth 10 m, scuba, coll. N.J. de Voogd, field nr. ROG046, 17 October 2016 ; RMNH Por. 11645, Mauritius, Rodrigues, Mourouk Ebony, Castel Rock , 19.76203°S 63.46273°E, depth 10 m, scuba, coll. N.J. de Voogd, field nr. ROG048, 17 October 2016 .

? Additionally : ZMA Por. 1 6368, Madagascar, Nosy Bé, Ambariobé, N of Kosy Komba, depth 6–8 m, scuba, coll. J.H. Stock, 28 December 1963.

Description. The in situ shape is a massive lumpy sponge ( Fig. 49a ) with irregular grooves and deep holes. Live color pale greyish white with pink rims in the peripheral parts. Surface irregular, in places somewhat conulose. Oscules inconspicuous, almost flush with the surface. Color of specimens on deck ( Fig. 49b–c ) and preserved ( Fig. 49d ) remains the same. Size of preserved specimens up to 13 x 8 x 8 cm, oscules 5 mm in diameter. Grooves and ridges up to 1 cm wide. Consistency coarse, harsh and hard.

Aquiferous system. Leuconoid.

Skeleton. A dense mass of giant triactines and small triactines. The oscules lead to into round atrial cavities lined with tetractines and triactines.

Spicules. ( Figs 50a–d ) Giant triactines, small triactines, tetractines.

Giant triactines ( Figs 50a ) equiradiate, equiangular, 408– 984 –1380 x 43 – 107.2 –204 µm.

Small triactines ( Figs 50b ) equiradiate, equiangular, 124– 186 –241 x 10 – 16.8 –22 µm; small sagittal triactines with wavy paired actines (not shown), 83– 106 –133 x 7 – 10.2 –14 µm.

Tetractines ( Figs 50c–d ) with basal triradiate system similar to triactines, 102– 163 –204 x 9 – 12.6 –16 µm, apical actines thin, curved ( Fig. 50d ), 29– 58 – 96 x 3 – 5.2 –8 µm.

Distribution and ecology. Rodrigues, possibly Madagascar, on reefs in shallow depth.

Etymology. Sulcatus (L.) meaning grooved, referring to the habitus.

Remarks. The spicule sizes and shapes are similar to those of Leucetta microraphis , to which the present species is most closely related. Two small irregular fragments of a white sponge, ZMA Por. 16368, collected near Nosy Bé, Madagascar, could belong to the present species based on its skeleton and spicules, but the small material without a definite shape precludes a definite conclusion.

We obtained sequences of the holotype and two of the paratypes and in our phylogenetic analysis ( Fig. 2C ) they grouped together (at 85% bootstrap value) in a larger clade containing sequences of L. microraphis from Mayotte, Madagascar, Australia and the Red Sea. Aligned and trimmed sequences of this larger L. microraphis - group (length 396 sites), showing 19 non-conserved sites, resulted in observed differences of 2–8 sites between L. sulcata sp.nov. and various sequences of L. microraphis s.l. The four sequences of L. sulcata sp.nov. shared two unique non-conserved sites. The three sequences of L. microraphis with pinkish red-brown-green color, described above from Mayotte and Madagascar, shared three unique non-conserved sites. These were not shared by the one Indonesian sequence of a specimen with similar morphology as the Mayotte and Madagascar specimens.

Remarkably, Oliver Voigt’s Red Sea sequences did not have any uniquely shared sites, individual sequences sharing non-conserved sites variously with L. sulcata sp.nov. or Western Indian Ocean L. microraphis , and the Australian and Indonesian sequences. Clearly, the morphological discrepancies and inconsistencies in L. microraphis s.l. are not easily solved by molecular sequence data. L. microraphis s.l. are likely a complex of sister species. The morphological differences of the present new species (white color, grooved and holed habitus) with L. microraphis s.s. (pinkish red-brown-green tubular masses) preclude conspecificity. The pink-white Red Sea specimens and L. pyriformis specimens described above are additional members of the group, differing in shape, color and e.g. in the long straight vs. curved condition of the apical actines of the tetractines. More study is necessary to differentiate the species.

Leocorny et al. (2016) recently studied the Leucetta species from (sub-)tropical Australian waters: Leucetta prolifera ( Carter, 1878) (originally as Teichonella ), L. insignis Row & Hozawa, 1931 , L. infrequens Row & Hôzawa, 1931 , L. expansa Row & Hôzawa, 1931 , L. villosa Wörheide & Hooper, 1999 , L. foliata Leocorny et al., 2016 and L. purpurea Leocorny et al., 2016 . Of these species, two are slightly similar to the new species in having a folded habitus, L. prolifera and L. foliata , but the former has the folds broadly bladed with rows of oscules on the upper surface of the folds, whereas the latter has the folds sharply and thinly bladed. Both do not really resembly the irregularly grooved-holed specimens of the new species. Both species have next to the usual complement of giant triactines, small triactines and small tetractines also large tetractines of the same size or larger as the giant triactines. The remaining species have a more compact or globular habitus, also unlike our new species: L. insignis is shaped like L. chagosensis but has tripod-like giant triactines, L. infrequens is a small erect clump, which apparently lacks small tetractines, L. expansa is also a small, but squat clump, possessing ectosomal microdiactines in addition to the usual spicule complement, L. villosa is provided with villous hair-like outgrowths on the surface, and finally L. purpurea is a small globular purple-colored sponge with giant tripods, sharing this feature with L. insignis .

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 49. Leucetta sulcata sp.nov., habitus in situ, on deck and preserved, a, holotype RMNH Por. 11639 in situ at Rodrigues, b, paratype RMNH Por. 11643, on deck, Rodrigues, c, paratype RMNH Por. 11645, on deck, Rodrigues, (photos N.J. de Voogd), d, paratype RMNH Por. 11643, preserved, Rodrigues.

FIGURE 50. Leucetta sulcata sp.nov., holotype RMNH Por. 11639 from Rodrigues, SEM images of the spicules, a, giant triactines, b, small triactines, c, tetractine, d, detail of tetractine showing thin curved apical actine.