GRANTIIDAE Dendy, 1892

Borojevic, Radovan, Boury-Esnault, Nicole & Vacelet, Jean, 2000, A revision of the supraspecific classification of the subclass Calcaronea (Porifera, class Calcarea), Zoosystema 22 (2), pp. 203-263 : 220-221

Family GRANTIIDAE Dendy, 1892

TYPE GENUS. — Grantia Fleming, 1828 by original designation.

DIAGNOSIS. — Leucosoleniida in which there is always a cortex, supported by a skeleton of tangential spicules that can be diactines, triactines, tetractines, or any combination of them. The aquiferous system is either syconoid with radial and elongate choanocyte chambers, or sylleibid or leuconoid with elongate or spherical, scattered choanocyte chambers. The inhalant and exhalant aquiferous systems are always fully developed. The choanoskeleton is articulate, tubular in syconoid species, and contains few to several rows of triactines and/or tetractines, or is, in leuconoid species, arranged without apparent order. In the latter case, the choanoskeleton always preserves traces of the radial organization, particularly at the level of the subatrial triactines and/or tetractines. The atrial skeleton consisting of tangential triactines and/or tetractines is well-developed.

DESCRIPTION

The family Grantiidae has a central position among the Leucosoleniida . Its major characteristic is the development of a distinct cortex. The development of a cortex is quite progressive in the Grantiidae , and simple forms, such as G. compressa (Fabricius, 1780) , clearly indicate their

cx ar proximity to Sycon by the presence of tufts of diactines at the end of their radial tubes. Indeed, in large Sycon species , the inhalant canals are partially closed by a membrane devoid of spicules. Formation of a specific skeleton in this membrane, with the production of tangential spicules which do not derive from those of the tubes, is a new feature which marks a major evolutionary step, and the boundary between the families Sycettidae and Grantiidae ( Fig. 18 ).

The family Grantiidae is very large. While some of the genera were designated to include sponges with a very particular type of growth or skeleton, and consequently include only a single species (e.g. Teichonopsis , Sycute , Synute ), others have a rather basic type of organization and skeleton, and include numerous species that are present throughout all the oceans (e.g. Grantia , Leucandra ).

Figures

FIG. 18. — Diagram of a transverse section through the wall of Grantia socialis Borojevic, 1967. Abbreviations: a, atrium; as, atrial skeleton composed of tangential triactines and tetractines; ss, subatrial spicules; ar, articulate choanosomal skeleton; cx, cortex (from Borojevic 1967a). Scale bar: 100 µm.