Weberella bursa (Müller, 1806) is a light-coloured, compact, globular sponge covered with short papillae. It is a deep water species.
Colour: Yellowish (alcohol); inside it is bluish white.
Shape, size, surface and consistency: Globular to massive, covered with papillae; usually the upper-side is somewhat flattened. Size up to 13 cm in diameter, but usually smaller, 2-10 cm. Papillae cylindrical, up to 5 mm high, 1 mm in diameter, but usually smaller. They are more numerous on the upper parts. Normally there are several dozens of papillae in a single specimen, but the number depends on size of the specimens. Most papillae bear a terminal oscule. The surface between the papillae is velvety, slightly hispid. Consistency compact, solid, firm.
Spicules: (Weberella bursa spics) Tylostyles in two clear categories, large ones of the choanosome, slightly fusiform, with ovoid, often mucronate heads, not very prominent: 330-700 x 5-16 µm; small ones of the ectosome, slightly curved, rounded heads: 125-270 x 2-6.5 µm.
Skeleton: There is a distinct cortex of 300-400 µm in thickness, strengthened by a palisade of small tylostyles at the periphery, lying on a mass of intercrossing single spicules, here and there united in bundles making a subectosomal reticulation. In the choanosome the large tylostyles are arranged in longitudinal spicule tracts.
Ecology: Fixed on stones, deep water, 62-932 m.
Distribution: Norway, North Atlantic; Artic down to the Mediterranean.
Etymology: bursa (Latin) = purse or bag, referring to the shape of the sponge. The genus name honours Dr Max Weber, director of the Zoological Museum of Amsterdam around the turn of the century, leading scientist of the Siboga Expedition (1899-1900) to Indonesian waters, and author of several papers on sponges.
Type specimen information: No type material in BMNH.
The combination of a globular shape, surface papillae and a solid consistency make this a very distinctive species. In the Mediterranean, a second species of Weberella is found with smaller spicules.
Source: Vosmaer, 1885