Clathrina biscayae, BOROJEVIC, 1987

Klautau, Michelle & Valentine, Clare, 2003, Revision of the genus Clathrina (Porifera, Calcarea), Zoological Journal of the Linnean Society 139 (1), pp. 1-62 : 10-11

CLATHRINA BISCAYAE BOROJEVIC &

BOURY- ESNAULT, 1987

Type locality: Bay of Biscay .

Type: MNHN-LBIM.C. 1985.3 (holotype /alcohol). Bay of Biscay (Station U 842: 44∞11¢ 3N, 8∞41¢ 2W at 500– 520 m depth). Collected by the N.O. Thalassa .

Clathrina biscayae was first described by Borojevic & Boury-Esnault in 1987. Several specimens of this species were collected in the Bay of Biscay at depths of 322–645 m, according to the authors. The holotype is deposited at MNHN under the registration number LBIM.C. 1985.3 .

Colour: White when preserved.

Description: Holotype is very small (0.5 ¥ 0.4 ¥ 0.2 cm). Cormus formed of large and irregular tubes ( Fig. 6A ). In the basal area the tubes are free, while in the apical area they are anastomosed and, sometimes, virtually fused. The skeleton comprises triactines and tetractines ( Fig. 6B ).

On the surface of the tubes, there are more triactines than tetractines. Some of the triactines are equiradiate and equiangular, but they are mainly pseudosagittal spicules. Actines of these external spicules are strongly conical, with sharp tips.

Inside the tubes, the tetractines are the most abundant spicules. Again, it is possible to find equiangular and equiradiate spicules, but they are very rare and the pseudosagittal spicules are the most abundant.

Two size classes of internal tetractines can be recognized according to the shape of the actines, which are slightly conical and sharp in one and more conical and sharp in the other.

The size of the unpaired actines is variable. Therefore, measurements were taken of the paired actines.

The apical actine of the tetractines is always shorter and thinner than the facial ones. Nevertheless, its size is very variable. The apical actine is very thin and sharp. It is smooth and straight or bent, normally in the direction of the paired actines.

Remarks: In the original description, the skeleton was described as comprising triactines and that ‘tetractines are occasionally added’, but that ‘in some specimens they can be present in relatively large numbers’. This is the case for the holotype of this species. Tetractines are the most abundant spicules, triactines being more abundant only in the external part of the tubes.

Borojevic and Boury-Esnault described three kinds of spicules: regular triactines, pseudosagittal triactines, and tetractines. We consider that there is a further spicule type, a second population of internal tetractines, characterized by a different size.

We also found thin trichoxeas on the surface of the tubes. These spicules were not mentioned in the original description; while they are not very abundant, we believe that they should be mentioned.

Figures

Figure 6. Clathrina biscayae. A, photograph of the holotype (¥ 10). B, triactines and tetractines. Scale bar = 100 Mm.