Thymosiopsis conglomerans, Vacelet & Borchiellini & Perez & Bultel-Poncé & Brouard & Guyot, 2000
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publication ID |
https://doi.org/ 10.5281/zenodo.5399304 |
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persistent identifier |
https://treatment.plazi.org/id/03C787D9-FFB0-5233-20D7-F9B547B7FA29 |
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treatment provided by |
Marcus |
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scientific name |
Thymosiopsis conglomerans |
| status |
sp. nov. |
Thymosiopsis conglomerans View in CoL n. sp.
TYPE MATERIAL. — Holotype: La Ciotat. Northwestern Mediterranean, near opening of 3PP cave, 17 m, 26.I.1998, one fragment (MNHN D JV 64). Paratype: same locality, 22.X.1998 (MNHN D JV 65).
ETYMOLOGY. — From conglomer, Latin, pertaining to the collecting properties of the sponge.
LOCALITY AND HABITAT. — The sponge is known only from the vicinity of the entrance of 3PP cave, 1.2 km South-West of La Ciotat on the French Mediterranean coast (43°09.47’N, 05°36.01’E). Three specimens have been observed and partly collected, 17-18 m deep on the floor of cliff recesses, 0.5 m in length. Two specimens live in the same recess, the third is a few metres distant. Despite its large size, the sponge was long overlooked numerous dives in this area, due to its subspherical shape similar to that of the surrounding pebbles and to its surface cover by algae, invertebrates and various debris. Contrary to what is observed in the homeotherm zone within the cave (Harmelin 1997), the sea water temperature in this place follows the normal seasonal variations (in 1998 from 13 to 23.5 °C at 18 m in depth instead of 13 to 14.5 °C within the cave at the same depth).
MORPHOLOGY
The type specimen ( Fig. 1A View FIG ) is massive, subspherical, 25 cm in maximum diameter and 15 cm high, with a large apical depression, approximately 4 to 6.5 cm in diameter, corresponding to an atrium in which most of the oscules are located. The two other specimens are somewhat smaller (25/15/ 10 cm), without a welldefined atrium. The color is whitish gray in surface and in the choanosome.
The surface is almost entirely covered by epizoic algae, invertebrates and a large variety of debris. Irregular low conules are determined by foreign material included in the sponge body. In the rare places that are free from debris or epizoic organisms, the surface is either smooth or bears low ridges connecting the conules ( Fig. 1B View FIG ). A cuticle is not macroscopically visible. Pore-sieves seem to be absent, but this is difficult to ascertain as they may be concealed by the extensive debris on the surface. The ostia have not been observed, probably due to the contracted state of the specimens. The oscules, 12 mm in maximum diameter, are mostly located inside the large apical depression, although a few are scattered on the lateral surface. Composite canals are visible within the oscules.
The texture is firm, but fleshy. The choanosome is dense, compact with a small number of canals. A proper skeleton is absent. Both the surface and the body of the sponge contain a large amount of foreign material, such as skeletons of calcareous algae, bryozoans, mollusc shells, Posidonia leaf fibres, sand grains, etc. ( Fig. 1C, D View FIG ).
An ectosomal layer from 50 to 400 µm thick is distinct from the choanosome in its low cell density and relative reinforcement by collagen fibrils ( Fig. 2A View FIG ). This layer, however, is not a resistant, well-defined cortex such as in Chondrosia or Chondrilla . The ectosome is outwardly lined either by an extremely thin (1 µm) cuticle or by a thin pinacoderm with T-shaped exopinacocytes. The pinacoderm appears to be present mostly in the areas bearing a reticulation of fine ridges. A few vacuolar cells are present near the surface, some of which have a short process extending toward the surface ( Fig. 2A View FIG ). The ectosome includes most cell types other than choanocytes, but in lower density than in the choanosome. A layer of elongate cells parallel to the surface, embedded in a moderately dense matrix of collagen fibrils with the same orientation, is often visible near the choanosomal boundary. Collagen bundles are poorly developed.
The choanosome has a higher cell density than the ectosome ( Fig. 2B, D View FIG ). Most of the choanosome volume is occupied by granular cells, which are closely pressed together in places. The choanocyte chambers are spherical or slightly ovoid, 24-40 µm in diameter, and belong to the aphodal type. The aphodus is up to 60 µm long and 12 µm in diameter. Numerous symbiotic bacteria are present in the intercellular spaces. The canals are moderately developed. Their walls are lined by vacuolar cells, which may lie under the endopinacocyte layer or within the lumen of the canals.
No stage of reproduction has been observed in the specimens, which were observed in January, August and October.
CYTOLOGY
The choanocytes are quite irregular in shape, 3.7 to 4 µm in size ( Fig. 2C, E View FIG ). The nucleus, 1.8 to 2 µm in diameter, is most often nucleolated(0.5-0.6 µm). There is no periflagellar sleeve. The cell body often displays lateral pseudopodia arising from below the collar and connecting neighboring cells ( Fig. 2C, D View FIG ). The collar is made up of 30 to 34 microvilli. Apopylar cells were not recognized. Although a few cells have been observed in the lumen of the choanocyte chambers, they are not definitely identified as central cells, due to the irregularity of the shape of the choanocyte layer. The choanocyte base generally emits short pseudopodia anchoring the cell in the underlying mesohyle. The aphodus is lined with endopinacocytes which are usually detached from the wall, probably a fixation artifact. Four distinct types of cells with inclusions have been observed:
Spherulous cells ( Fig. 2F View FIG ), 6-14 µm in diameter, contain about 10 homogeneous, dense spherules, 2-4 µm in diameter, which occupy most of the cytoplasm volume. The anucleolate nucleus is 2 µm in diameter. Probably less mature stages have a higher volume of cytoplasm free from inclusion and a higher number of spherules irregular in size, some of them as small as 1 µm. Spherulous cells are dispersed in the ectosome and the choanosome. Granular cells (Fig. 3A, B, F), 10-18 µm, with a small anucleolate nucleus 1.8 µm in diameter, contain numerous dense granules with an irregular outline, 0.5-1 µm in diameter, enclosed in clear vesicles delimited by a thin sheet of cytoplasm. The smaller cells are denser than the large ones, which have a clear cytoplasm in which the dense regular sized granules are conspicuous. Degenerative stages of the granules have not been observed. Granular cells are very abundant in most regions and may occur in dense clusters.
Vacuolar cells (Fig. 3C), 8-10 µm in diameter, usually display a single vacuole, 6 µm in diameter, containing a large spherical inclusion with homogeneous, dense contents, lined by a thin empty space. The vacuole is surrounded by a cytoplasm layer 0.1-0.7 µm in thickness, with a small nucleus (less than 1 µm) and mitochondria. A few cells have two or more vacuoles. The inclusion stains green with toluidine blue. The vacuolar cells, rare in the choanosomal tissue, are mostly found around the canals, with some of them migrating through the pinacocyte layer towards the canal lumen ( Figs 2D View FIG ; 3C). A few of them have been observed in the most superficial layer of the ectosome, with an extension of the cell, including the vacuole, toward the surface ( Fig. 2A View FIG ). Such cells are reminiscent of the “flaskshaped cells” described in the ectosome of dictyoceratids (Bidder 1892; Burck 1909).
Microgranular cells (Fig. 3D), 5 µm in maximum size, with an anucleolate nucleus 1.8 µm in diameter and with long pseudopodia, contain very dense, ovoid inclusions, 0.2 µm/0.8 µm, in the cytoplasm. Microgranular cells are dispersed throughout the sponge tissue.
Collagen fibrils (Fig. 3E) are loosely organized in thin bundles which are especially visible in a narrow zone between ectosome and choanosome. There is no disjunction between the collagen bundles and a granulo-fibrillar matrix such as is observed in some species of Halisarca or Chondrillidae (Vacelet & Donadey 1987) . The fibrils are unusually thin, approximately 9 nm in diameter, with a faint periodic striation, and resemble the smooth type of collagen fibrils (Garrone 1978).
Symbiotic bacteria, rare and dispersed in the ectosome, are numerous in the choanosome ( Figs 2D View FIG ; 3F). They are extracellular and display the high morphological diversity usually found in most massive Demospongiae, varying in size (on sections) from 0.2-0.4 µm in diameter to 0.7- 2.4 µm in length.
IG
SEQUENCE COMPARISON
The sequences of 28S rRNA of Thymosiopsis conglomerans , T. cuticulatus and Thymosia guernei were compared with existing sequences from several representatives of sponges extracted from GenBank. Phylogenetic trees were constructed by both neighbour-joining ( Fig. 4 View FIG ) and parsimony (data not shown). The two methods yielded identical branching orders.
These methods are not well suited to the distinction of taxa at the species level and the differences between the two species of Thymosiopsis appear slight and could be considered as insignificant.The genus Thymosiopsis forms a clade with Thymosia with a high degree of reliability, i.e. in 100% of the bootstraps. The two genera Thymosia and Thymosiopsis form a clade with the representative of family Chondrillidae , Chondrosia reniformis , with Haplosclerida as an outgroup. This clade is supported by a high bootstrap value (98%).
STEROLS
The new species T. conglomerans was shown to contain two new ∆ 7 sterols, thymosiosterol and ∆ 24 thymosiosterol, bearing unusual side-chains (Bultel-Poncé et al. 1999).
Thymosiopsis cuticulatus also contains unusual ∆ 7 sterols. GC-MS analysis revealed the presence of a major sterol (95%), (RT 48.2) m/z 426 (M +) (29), 411 (13), 393 (2), 314 (5), 299 (6), 271 (100), 255 (8), 246 (6), 231 (13), 213 (22), accompanied by sterols having M + 426 (RT 49.9, 4%), M + 440 (RT 52.8, 2%). Due to the paucity of the available material, NMR data were recorded from the crude sterol fraction. 1 H NMR data displayed a broad doublet at δ 5.13 ppm (J = 1.3 Hz) characteristic of a ∆ 7 vinyl proton, in addition to signals at δ 4.72 and 4.66 (two singlets) indicative of a terminal methylene group. Three doublets centered at δ 1.00 ppm (6H), 0.99 (3H), 0.89 (3H) ppm respectively indicate the presence of only methyl groups as substituents. The two singlets at δ 0.77 and 0.50 ppm assigned to C-19 and C-18 protons confirm the ∆ 7 unsaturation. All these data are reminiscent of those described for pulchrasterol (Crist et al. 1983) (Fig. 5).
Table 1 gives the chemical shifts of the methyl groups of the main sterols of T. cuticulatus , 3, in comparison with those of sterols of T. conglomerans 1 and 2 and pulchrasterol 4. A COSY experiment allowed confirmation of the chemical shifts of CH 3-29 and 30 at δ 1.00 (d, 6H), coupled with H-26 at δ 2.17 and CH 3 -27 at d 0.99 (δ, 3H) coupled to H-24 at δ 1.97 ppm. HMBC experiment furnished correlations between CH 3 -27, 29, 30 protons, H-26 and H-24 with C-25 (δ 163.2), confirming the position of the substituents. Combination of COSY and heteronuclear correlations (HMBC) experiments shows that the main sterol of T. cuticulatus was 24,26,26-trimethylcholesta-7,25(27)-dien-3β- ol. The minor sterols (less than 5% of the total sterol content) were not identified.
Thymosia guernei (specimens from Portugal) contains cholestanol as the sole sterol: EIMS: m/z 388 (M +). 1 H NMR data were in agreement with literature data.
CYTOLOGY OF THYMOSIA GUERNEI
Some observations have been made on the cytology of Thymosia guernei using specimens from Portugal ( Fig. 6 View FIG ), redescribed by Rosell (1988). This species shares some cytological characters with both species of Thymosiopsis , although it lacks the diagnostic granular cells. A few vacuolar cells with the same characters as in Thymosiopsis are present. The spherulous cells are more numerous, with homogeneous spherules which can be significantly larger than those of Thymosiopsis (up to 8 µm). The choanocyte chambers and choanocytes are similar in shape to those of Thymosiopsis .
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