Polymastia Bowerbank, 1864

Morrow, Christine & Boury-Esnault, Nicole, 2000, Redescription of the type species of the genus Polymastia Bowerbank, 1864 (Porifera, Demospongiae, Hadromerida), Zoosystema 22 (2), pp. 327-335 : 329-332

publication ID	https://doi.org/ 10.5281/zenodo.5401907
persistent identifier	https://treatment.plazi.org/id/03EE1E1C-9B30-FFE1-C2EC-0570FDABFE62
treatment provided by	Marcus
scientific name	Polymastia Bowerbank, 1864
status

Treatment

Polymastia Bowerbank, 1864 View in CoL

Polymastia Bowerbank, 1864: 177 ; type species Halichondria (Spongia) mamillaris by original designation

Pencillaria Gray, 1867: 527 ; type species Spongia mamillaris by original designation

Rinalda Schmidt, 1870: 51 ; type species Rinalda uberrima by original designation

DIAGNOSIS

Polymastiidae , thickly encrusting, spherical or cushion-shaped, always with papillae. Skeleton composed of radial tracts of principal spicules between which free spicules are scattered. Cortex composed of at least two layers, the superficial layer is a palisade of small tylostyles, the lower layer is made of intermediary spicules, tangential, semi-tangential or perpendicular to the surface. Exotyles echinating the surface may be present. The principal spicules can be tylostyles, subtylostyles, styles, or strongyloxeas, intermediary spicules are most often tylostyles, and ectosomal spicules are always tylostyles.

Polymastia mamillaris (Müller, 1806) ( Figs 1 View FIG ; 2 View FIG D-F)

Spongia mamillaris Müller, 1806: 44 . – transferred by Bowerbank 1864: 177.

HOLOTYPE. — Bohuslän. North Atlantic (Swedish west coast), 58 ° 15 ’N, 11°50’E, 2.I.1993, Zoological Museum in Copenhagen (Denmark), labelled Riksmuseel Stockholm.

OTHER SPECIMENS. — From the Zoologisk Museum Copenhagen collected on the Swedish west coast: Björms Rev. 120-200 m, 11. VII.1975.

Ulvillarna. 150-225 m, 21. III.1977.

East of Ramsô. 99- 108 m, 16.V.1974.

Säcken. 76 m, 13.05.1974; 80-90 m, 16.X.1974.

TYPE LOCALITY. — North Atlantic coast: Sweden coast 58°15’, 11°50’E.

DESCRIPTION

External characters

The type specimen is a fragment of a cushionshaped, attached sponge approximately 35 × 18 × 7 mm thick. The upper surface is hispid. The surface of the sponge traps silt and the colour is only discernible on the papillae. The color is cream in alcohol. The specimen has 26 inhalant papillae and one exhalant. The mean length of the inhalant papillae is 8 × 2 mm in diameter. The exhalant papilla is 11 mm long and approximately 4 mm in diameter.

Skeleton ( Fig. 1 View FIG )

The ectosomal skeleton is about 400 µm thick and composed of three layers: the upper layer is a dense palisade (≈ 300 µm thick) of fusiform tylostyles, the middle layer is collagenous (≈ 20 µm thick) and the lower layer is a tangential layer (≈ 80 µm thick) made of intermediary spicules.

Choanosomal tracts of principal spicules are 53- 106 µ m thick. These tracts are divided into two to three smaller ones below the ectosome. They cross the ectosome and echinate the surface by approximately 875 µm. Groups from two to five ectosomal spicules are scattered between the choanosomal tracts. They are particularly abundant below the tangential layer of intermediary spicules in a layer approximately 500 µm thick.

The skeleton of the inhalant papillae consists of ascending multispicular megasclere tracts that run the length of the papillae. These are support- ed by a network of intermediary tylostyles arranged perpendicularly to the megascleres tracts. Towards the periphery there is a layer of tangentially arranged intermediary tylostyles and external to this a palisade composed of ectosomal tylostyles.

Spicules ( Fig. 2 View FIG D-F)

Ectosomal tylostyles are fusiform, straight or slightly bent with a well-marked head: 143- 196/5.3-16 µm (mean 169/10.6 µm, N> 50). Intermediary styles or subtylostyles, straight 243- 561/8-15.9 µm (mean 445/13.2 µm, N> 50).

Principal spicules are straight, fusiform strongyloxeas, 742-1378/8-32 µ m (mean 1052-24.5 µ m, N> 50).

REMARKS

We have the opportunity, thanks to our colleague Ole Tendal, to reexamine specimens of Polymastia from the Swedish west coast collected between 76 and 225 m deep. These specimens correspond to the type of Müller: ectosomal skeleton composed of three layers, groups from two to five ectosomal spicules scattered between the choanosomal tracts and particularly abundant below the tangential layer of the ectosome, shape of the ectosomal tylostyles (101-182/5.2-11.7, mean 148/8.4 µm, N> 50) and of the principal choanosomal spicules (strongyloxeas 461-1320/10.6-26.5, mean 853/20 µm, N> 50).

On the other hand, the type specimen of Polymastia mamillaris does not correspond with what is commonly called P. mamillaris in the North East Atlantic (Channel, North Sea, Irish Sea). The North East Atlantic common Polymastia has a two-layered cortex, free intermediary tylostyles in the choanosome and the shape of spicules is not fusiform (detailed description in Boury-Esnault 1974, 1987).

Polymastia penicillus (Montagu, 1818) ( Figs 2 View FIG A-C; 3)

Spongia penicillus Montagu, 1818: 93

not Polymastia penicillus Vosmaer 1882: 26 View in CoL . – Levinsen 1886: 346. – Fristedt 1887: 434 (in fact Trichostemma hemisphaericum View in CoL ).

HOLOTYPE. — BMNH 30.7 .3.26 from a specimen of Montagu in the Dr Grant Cabinet.

OTHER SPECIMENS. — From the South coast of the Channel Sea (Aber Benoit, intertidal zone NBE coll.) and Irish coast ( CM coll.).

TYPE LOCALITY. — Precise type locality unknown. The specimen was obtained by dredging on the coast of Devon ( Great Britain).

DESCRIPTION

External characters

The type specimen is whole dry and is a small piece with few papillae. This does not allow to give a description of the external characters. Montagu (1818) described this specimen as yellowish and gave a drawing of the external shape (Montagu 1818: pl. 13, fig. 7).

Skeleton ( Fig. 3 View FIG ).

The ectosomal skeleton is about 500 µ m thick and composed of two layers. The external one is a palisade (≈ 170 µm thick) of ectosomal tylostyles perpendicular to the surface and which lays directly on the internal tangential layer (≈ 340 µm thick) of intermediary tylostyles.

The choanosomal skeleton consists of multispicular tracts of principal tylostyles perpendicular to the surface which they pass through. Free intermediary tylostyles are scattered between these tracts.

The principal skeleton of the papillae is composed of longitudinal tracts of principal tylostyles. They are the extension of the tracts from the choanosome. From the outside to the inside, the skeleton of the papillae is composed of a palisade of ectosomal tylostyles, a tangential layer of intermediary tylostyles which are in continuity with that of the main body, and the longitudinal tracts.

Spicules ( Fig. 2 View FIG A-C)

Ectosomal tylostyles straight or slightly bent with a well-marked head: 154-201/1.5-4 µm (mean 175/2.5 µm, N> 50).

Intermediary tylostyles straight or slightly bent with a head more or less marked: 300-715/8- 11 µm (mean 507/10 µm, N> 50).

Principal tylostyles straight or slightly bent with a head more or less marked: 874-1543/8-12 µm (mean 1080/10 µm, N> 50).

REMARKS

The studied specimen of P. penicillus is the specimen BMNH (30.7.3.26) from Montagu collection in the Dr Grant Cabinet. We formally designed this specimen as the type specimen of Polymastia penicillus . The common Polymastia species from the NE Atlantic coast corresponds exactly with this species (Boury-Esnault 1974, 1987; personal collections of the authors from Irish coast and Channel Sea) and with the specimens (BMNH 1910.1.1.8 and BMNH 1930.7.3.3) from the Bowerbank collection and identified by Bowerbank as P. mamillaris .