Tethya norvegica Bowerbank, 1872


Family : Tethyidae

Form: Tethya norvegica Bowerbank (1872) is a small globular yellow sponge with warty surface. Differences with T. citrina and T. hibernica are microscopical. Normally spherical, diameter 1-2 cm.

Colour: Yellow.

Consistency: resilient but somewhat fragile, not hard.

Surface: Surface with contiguous, conulose papillae. Some specimens carry a few large, pedunculate buds 1-2 mm in diameter. Cortex thin, 1 mm in depth in a sponge of 1 cm diameter.

Internal characters

Skeleton: The radiate bundles of styles (strongyloxeas) are dense, each one terminating in a cortical papilla surrounded distally by a small fan of slender styles. The bundles are often spirally arranged. The megasters are located in the cortex, mainly in the outer layer with a sparse and irregular distribution. The micrasters form a dense sheet under the surface of the sponge and are also abundant both in the cortex and in the medulla. No morphological differentiation has been observed between the cortical and medullar micrasters but there is a slight difference in size with the smaller micrasters being found more frequently in the cortex than in the medulla.

Spicules: Megascleres: Principal styles (strongyloxeas) 1200-1500 x 20 μm with the proximal end often slightly enlarged (subtylostyles). Slender styles 500-700 x 5-10 μm. Microscleres: Megasters-spherasters 20-60 μm (mainly 30-50 μm) with ratio of ray/centre (R/C)= 0.8-1 and a variable number of rays (generally about 15) frequently with spines, divided ends or other irregularities Micrasters: oxyasters and rare strongylasters 6-15 μm (mainly 8-12 μm) with 8-12 almost smooth rays and an occasionally slightly developed centre.

Distribution: Apparently replaces the common European "orange sponge" (T. citrina, formerly T. aurantium) in the Northern and Arctic Atlantic. Norway, White Sea, Bear Island, Spitzbergen, Novaja Zemlja, Iceland, The Faroes, Scotland, Skagerrak.

Identity: The species differs from T. citrina in size (only up to 2 cm in diameter), the megasters are generally much smaller and their RC ratio is high, i.e. they have less pronounced centres.

Editors: Christine Morrow, Bernard Picton & Rob van Soest.

 Picton, B.E., Morrow, C.C. & van Soest, R.W.B., 2011. [In] Sponges of Britain and Ireland