Rapp, Klautau & Valentine, 2001
Clathrina cribrata Rapp et al. 2001) is a very characteristic calcareous sponge which has a large number of open tubes and closed erected above the main mass of anastomosed tubes, unlike most other Clathrina species. Spicules are exclusively small triactines.
Colour: Preserved specimen is beige.
Shape: Massive size. The cormus is formed of
large, irregular and loosely anastomosed tubes. However, the anastomosis is not typical of Clathrina in the apical region, but similar to that of Soleneiscus. On the surface of the cormus, tubes are no longer anastomosed, but distally ramified. Some of them end in a cul-de-sac, while others are open-ended and work as oscula. Inside these oscula, which are simple apertures, there is always a sieve formed by spread cells, with oval apertures measuring 17-27 µm. Here they lie in a monolayer, probably to protect the sponge against the invasion of foreign organisms.
Spicules: are only triactines, of homogeneous size, 47-75 x 6 µm. They are equiangular and equiradiate. Actines are cylindrical, slightly undulated, with a blunt tip.
Skeleton: The wall of the tubes is thin (25 µm), and its skeleton has no organization.
Distribution: Kristiansund, Norway.
Type: BMNH 19126.96.36.199 (holotype/alcohol). Kristiansund, Norway. Trondheim Museum Exchange (Collection number T.28).
C. cribrata is very different from all the other species of Clathrina. The organization of the cormus is the character that makes it so unusual. The original authors were doubtful if it was a true Clathrina or a Soleneiscus. However, as the anastomosis of the tubes is characteristic of Clathrina, becoming similar to Soleneiscus
only at the apical region, it was decided to describe it as such. Another peculiar characteristic is the large number of open or closed terminal tubes at the surface and the existence of the mesh of cells (cribriform membrane) below the opened tubes (oscula). Further studies on these morphological characters are required. It has been suggested that the presence of a mesh below the oscula could have the function of a sphincter, permitting the sponge to close oscula at low tide.
Source: Klautau & Valentine, 2003.