Tethya ornata, 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 : 347

Tethya ornata n. sp.

TYPE MATERIAL. — Holotype ( MSNG 49675 ).

ETYMOLOGY. — After the frequent occurrence of spines and other anomalies of the spherasters.

TYPE LOCALITY. — Coconut Island. Hawaii, under floating dock, 0.5 m, 7.XII.1985, coll. P. Karuso.

DESCRIPTION

Morphology

Body globose ( Fig. 1A ), a little ellipsoidal with axes of 2.5 and 3 cm. Tubercles small, less than 1 mm high, and irregularly conical. Several tubercles support small stalked buds. Yellow ochre in alcohol, consistency firm. Choanosomal cavities host commensal polychaetes.

Skeleton ( Fig. 2 )

Megasclere bundles stout and not apically branched. Spherasters fill the middle and inner cortical layers, with larger spicules in the middle one. Few spherasters in the outer layer and absent in the choanosome. Micrasters cover the sponge surface ( Fig. 1C ) and the cavities and channels of the cortex and choanosome.

Spicules

Megascleres. ( Fig. 1B ) Main strongyloxeas 600- 1600 × 10-25 µm and auxiliary strongyloxeas, often transformed in anisostrongyles and styles, 300-800 × 4-18 µm. The two categories, howev- er, intergrade.

Megasters. Spherasters 25-100 µm in diameter, R/C (ratio between ray length and centre diameter) = 0.2-1.5. Their shape, as their size, is extremely variable ( Fig. 1 D-F). Their rays, 15-20, are very frequently spined, forked or truncated at the tip, sometimes bent or shortened and rounded. Each spheraster may express a different set of these abnormal traits. Normal spherasters are more frequent among the small spicules. Abnormal spherasters are the large majority of the full grown spicules. The rare large normal spherasters show 90-100 µm in diameter and R/C = 1.

Micrasters. Generally tylasters ( Fig. 1 G-H), sometimes strongylasters similar in the cortex and choanosome. Generally 6-8 µm in diameter, but their size is heterogeneous with a range of 2-15 µm including some very small or large asters. Also their shape is variable and dependent on the presence or absence of an enlarged centrum, and by the development of the knob at the tips of the rays. There are eight to twelve rays and these generally have a well-developed spiny knob at the tip. Some very small micrasters are irregularly shaped.

REMARKS

T. ornata is well characterized by the spinosity and other anomalies of the majority of its megasters, an exception in the genus Tethya . Only another species of Tethya , T. tethya , an encrusting species from the Hawaii Aquarium of Honolulu, has been described for the Hawaii Islands (Laubenfels 1954). It differs from T. ornata for its smaller spherasters without spines and the presence of oxyasters among the micrasters. One of us (Sarà) has studied one specimen collected at Oahu, Black Point, labelled “ Tethya japonica ”, in the California Academy of Sciences, Natural History Museum. Spicular slides show that it is not T. japonica but more likely T. deformis (Thiele 1898) . Unfortunately, without a comparison with the type of T. deformis recorded for the Museum für Naturkunde of Berlin but until now not found, we cannot be sure on this determination.

Figures

FIG. 1. — Tethya ornata; A, holotype; B, strongyloxeas; C, the superficial layer of tylasters; D, the variable shape of ornate megasters; E, F, SEM views of megasters; G, H, SEM views of tylasters. Scale bars: A, 6 mm; B, 130 µm; C, 15 µm; D, 30 µm; E, 8 µm; F, 25 µm; G, 2.5 µm; H, 1.5 µm.

FIG. 2. — Tethya ornata, schematic drawing of the skeletal arrangement. Scale bar: 0.4 mm.