Swartschewskia papyracea (Dybowski, 1880)

Bukshuk, Natalia A. & Maikova, Olga O., 2020, A new species of Baikal endemic sponges (Porifera, Demospongiae, Spongillida, Lubomirskiidae), ZooKeys 906, pp. 113-130 : 113

Swartschewskia papyracea (Dybowski, 1880) Figs 1 , 5 ; Tables 1, 2

Note.

The morphology of three specimens of S. papyracea sampled in the Olkhonskiye Vorota Strait was examined.

Description.

Body shape is globose. The sponge often has a single osculum but several oscula are also possible. Mostly the oscula look like round pits with 3-5 exhalant apertures on the bottom. One specimen bears a sieve-like osculum that consists of a number of exhalant apertures not deepened relatively to sponge surface. Distribution of dermal pores is uniform. Inhalant apertures are observed almost in every meshes of ectosomal skeleton network. One mesh contains 1-5 round or ovoid apertures, 5-(28)-87 × 6-(35)-102 µm in size. Exhalant apertures in the sieve-like osculum have elongated or round shape, 214-(281)-357 × 178-(219)-286 µm in size.

The ectosomal skeleton is a high ordered alveolar network, mesh shape resembles a convex polygon. There are no parts with a disordered network structure. Megascleres in tracts are arranged in dense bundles, 6-12 megascleres in every bundle.

Megascleres are stout and bent strongyles of 93-(117)-138 × 13-(17)-22 µm. Analysis of the fine morphological structure of S. papyracea spicules indicated the presence of only two sorts of spines: rosette spines and isolated simple spines. Rosette spines are slightly elongated, 0.5-(1.4)-3.2 × 0.6-(1.6)-4.1 µm, and contain 4 - 18 simple spines. Isolated spines and simple spines in rosettes have a similar size of 0.1-(0.4)-0.9 µm.

Figures

Figure 1. Sampling sites in Lake Baikal: 1, 2 samples of S. khanaevi sp. nov, 3 samples of S. papyracea.

Figure 5. Swartschewskia papyracea A sponge surface B ectosomal skeleton C cross section of skeleton D rosette spines on strongyles E strongyles. Abbreviations: chs choanosomal skeleton, dm dermal membrane, es ectosomal skeleton, ia inhalant apertures, st spicular tracts. Scale bars: 10 μm (D), 100 μm (E), 500 μm (A, C), 1 mm (B).