Vosmaeropsis hozawai, Borojevic & Klautau, 2000

Borojevic, Radovan & Klautau, Michelle, 2000, Calcareous sponges from New Caledonia, Zoosystema 22 (2), pp. 187-201 : 198-199

Vosmaeropsis hozawai n. sp.

TYPE MATERIAL. — Holotype MNHN-LBIM-C- 1999-04.

ETYMOLOGY. — The name of the species is proposed to acknowledge the excellent descriptions of a series of Vosmaeropsis from Japan and from the Hamburg Museum collections provided by the late Professor Sanji Hôzawa.

MATERIAL EXAMINED. — One specimen.

TYPE LOCALITY. — Banc Gail, stn 114.

LOCALITY. — South-west coast, Banc Gail, stn 114, 25- 30 m.

DESCRIPTION

The collection contains one large dark brown specimen, partially fragmented, but which was originally more than 5 cm high. It is sac-shaped, flattened and folded with a single apical naked osculum. The external surface is smooth but harsh. The cortical skeleton is composed of tangential triactines of variable size arranged without any order. The largest ones are easily seen under low magnification. The sponge wall is 2-5 mm thick. It surrounds a large atrial cavity that has a smooth surface, pierced by openings of large exhalant cavities and smaller exhalant canals. The sponge wall is hard, composed of a strong skeleton, which supports a choanosome with a leuconoid organization. Branching exhalant canals permeate the internal part of the choanosome.

The skeleton contains only triactines and is divided into two regions. The subcortical region has a clearly radially arranged skeleton, containing large pseudosagittal subcortical spicules with one of the paired actines pointing towards the atrium. In the same region, large choanosomal triactines point their unpaired actine towards the cortex. The subjacent internal region of the choanosome, in which exhalant canals are irregularly scattered, has no defined orientation of spicules. No defined layer of subatrial spicules can be identified in the vicinity of the atrial surface. Very large, nearly equiangular, triactines are irregularly scattered throughout the sponge wall. The atrial skeleton and that of the exhalant cavities contain triactines similar in form to those of the cortex, but smaller.

Spicules

The giant triactines of the choanosome measure up to 1500 / 100 µm. They are equiangular and equiradiate, with conical sharp actines. Smaller sagittal spicules are also present in the choanosome. The pseudosagittal subcortical spicules measure 650 (± 120) / 47 (± 15) µm. These pseudosagittal spicules are similar to the choanosomal ones, with only a slight difference in the length and in the curvature of the paired actines. The cortical and atrial triactines which are of variable size, have paired actines bent in form of an arc, and the unpaired one is straight. They are approximately of a similar length, 420 (± 230) / 47 (± 22) µm.

REMARKS

Vosmaeropsis hozawai is probably close to V. triradiata Hôzawa, 1940 described from Mexico. These two species share the characteristic of having neither diactine nor tetractine spicules, which distinguishes them from all the other Vosmaeropsis species. Vosmaeropsis triradiata is characterized by the fact that the largest triactines are found in the cortex, whilst in V. hozawai the giant choanosomal triactines are much larger than those observed in the cortex. Hôzawa (1940) also pointed out that the organization of the choanosome is sylleibid in V. triradiata , whilst the choanosome of V. hozawai is thick and leuconoid.

The external layer of V. hozawai exhibits the typical structure of the Heteropiidae , with subcortical pseudosagittal spicules facing the regular layer of sagittal spicules, whose unpaired actines point towards the cortex. Conversely, the innermost part of the choanosome is permeated by exhalant canals and has an irregular organization. We believe that this layer is a secondary structure with a proper secondary skeleton that supports a region intercalated between the original subatrial and atrial regions. This interpretation is suggested by the fact that the choanosomal spicules that face the subcortical pseudosagittal ones retain the form and remain in the position of subatrial spicules, although they are separated from the atrial surface by the exhalant canal-containing layer. In accordance with this hypothesis, there are no true subatrial triactines associated with the atrial skeleton.