Scalarispongia scalaris Schmidt (1862), also known as Cacospongia scalaris, is a massive, lobate, occasionally globular sponge with conulose surface. It is dark coloured (blackish or violet-brownish) on the upper parts, whitish yellow on the sides and lower parts. It is compressible, but firm, and—although related to Spongia spp.—it has no bath sponge properties. It is a Mediterranean species reported also from the Atlantic coasts of Portugal.
Colour: Blackish (scalarispongia_carbal.jpg) or violet-brown on top, whitish yellow on the sides and lower parts; in caves the latter color occurs all-over.
Shape, size, surface and consistency: Massive-lobate, occasionally globular. Size up to 15-20 cm in diameter, 1.5-3 cm thick. Surface regularly and prominently conulose, with conules 0.5-1.5 mm high spaced 1-2 mm apart. The "skin" is easily removed. Oscules on small elevations or lobules, 1-3 mm in diameter. Often infested with parasitic barnacles of the genus Acasta. Consistency compressible, almost soft and easily damaged when alive; firm when preserved, hard when dried.
Skeleton: (scalarispongia_fibres.jpg) Primary fibres and secondary fibres connect at more or less right angles giving a ladder-like aspect. Primary fibres made up of a hard type of spongin; they are clearly stratified and have a core of foreign material, but where this is less extensive a distinct pith is visible, size 90-200 µm in diameter. Secondary fibres free of inclusions, but with pith in the form of a fibrillar substance; they are clearly stratified, and their diameter is 30-80 µm.
Choanocyte chambers: Spherical, 30-35 µm in diameter.
Reproduction: Embryos were found in Mediterranean specimens between April and October.
Ecology: Shallow-water down to 250 m. It can come up almost to the low water mark.
Distribution: Mid-Portugal; Mediterranean.
Etymology: scala (Latin) = ladder, referring to the regular ladder-like skeletal reticulation.
Type specimen information: Several type specimens are kept in the Graz Museum, LMJG 15406, 15409-10, 15416, 15475, 15479 and 15485.
This is a distinct species which can be easily distinguished from the bath sponges by its ladder-like skeleton.
Source: Vacelet, 1959.