Tethya strongylata, Sarà & Bavestrello & Calcinai, 2000

Sarà, Michele, Bavestrello, Giorgio & Calcinai, Barbara, 2000, New Tethya species (Porifera, Demospongiae) from the Pacific area, Zoosystema 22 (2), pp. 345-354 : 349-351

Tethya strongylata n. sp.

TYPE MATERIAL. — Syntypes ( BMNH 1938:4:8:1, slide 1938:4:8).

ETYMOLOGY. — For the occurrence of many strongyles in the spicule complement some of which are very short and plump.

TYPE LOCALITY. — Galapagos Islands. West side of James Island.

DESCRIPTION

Morphology

The two specimens are globose and respectively of 2 and 3 cm in diameter. The larger specimen has a large bud of 8 mm in diameter attached to the mother sponge by a short peduncle 2 mm long. Tubercles flattened and cortex with lacunae.

Skeleton ( Fig. 5)

Radial megasclere bundles not branched. Spherasters throughout the whole cortex, more densely in the inner layer ( Fig. 6A ). Some small spherasters in the choanosome. Sponge surface covered by cortical micrasters.

Spicules

Megascleres. Strongyloxeas ( Fig. 6B ) or anisostrongyles ( Fig. 6C ) frequently shortened, 500- 2000 × 18-33 µm. Some spicules are short and plump strongyles, anisostrongyles and styles ( Fig. 6D, E, G ) 140-300 × 40-60 µm.

Megasters. ( Fig. 6F ) Spherasters with short rays, in the cortex 40-85 µm and in the choanosome 35-48 µm in diameter, R/C = 0.1-0.7, frequently 0.5. Rays may be distorted, forked, spined or reduced to hemispherical outgrowths ( Fig. 6H ), often with different ray aspects in the same spicule. Ray number 24-30.

Micrasters. ( Fig. 6I, J ) Tylasters 10-14 µm in diameter, generally 11-12 µm. As the rays are entirely spined the apical knob, a little more densely spined, is not distinct. Some tylasters have a small centrum. Ray number generally 12-14.

REMARKS

T. strongylata is characterized by the shortened megascleres which are often anisostrongyles with some short and plump strongyles and styles. The megasters are also peculiar as they are frequently reduced and irregular. The rays are unusually short and numerous. In contrast, micrasters show a great uniformity in size and shape. They differ from the T. japonica Sollas, 1888 tylasters for their greater size, number and robustness of rays, and from those of T. deformis Thiele, 1898 for the less frequent and smaller development of the centrum. T. strongylata is the second species of Tethya described for the Galapagos Islands. The other species is T. sarai Desqueroux-Faundez & Van Soest, 1997 which is distinguished from strongylata not only by the lack of the peculiar traits of this species but also in possessing a category of choanosomal strongylasters/tylasters which are well distinguished from the cortical tylasters.

Figures

FIG. 6. — Tethya strongylata; A, the cortical region showing the megaster distribution; B-E, megascleres showing different steps of lenght reduction and width increase; F, megasters; G, a very short and plump strongyle; H, SEM view of a megaster; I, J, SEM views of tylasters. Scale bars: A, 250 µm; B, 300 µm; C-E, 60 µm; F, 50 µm; G, 25 µm; H, 11 µm; I, 2 µm; J, 4 µm.