Picton & Goodwin, 2007
Spongosorites calcicola Picton & Goodwin (2007) is a bright yellow massive sponge with large oscules and a smooth surface. It was recently described from Rathlin Island, Northern Ireland. It is one of several closely similar species of Spongosorites occurring in deeper waters. Differences are shades of colour, post-collecting changes and spicule sizes and form.
Colour: Bright lemon yellow.
Shape, size, surface and consistency: Massive sponge with large oscules. Forms a thick crust with a shiny, rubbery appearance. Patches can be fairly large, some >20 cm maximum diameter. Unlike many other species in this genus it does not undergo a colour change when removed from water.
Spicules: There is a single type of spicule, slightly bent oxeas (50-410 by 4-10 µm) most of which have bluntly pointed, mucronate ends. In a few of these one or both ends are rounded, giving these spicules a style- or strongyle-like form. The width of the spicules is generally proportional to the length with the shorter ones being substantially thinner than the longest; however,occasionally long thin spicules are present. The spicules are straight or slightly curved.
Skeleton: Thick ectosomal layer >1000 µm in some places, a dense mesh mainly composed of smaller oxeas (< 200 µm). Choanosome is a disordered mass of oxeas of both large and small sizes, mesh is less dense than that of the ectosome.
Ecology: On limestone bedrock, in deeper water 26-32 m.
Distribution: So far known only from Rathlin Island, Northern Ireland.
Type material: Holotype: [Mc2482]. Sample in IMS, section and spicule preparation, White Cliffs (55°17.499'N 006°14.762'W; water depth: 27-32 m); coll. by B.E.Picton and C.E.Goodwin, 15 June 2005.
Etymology: From the latin calci meaning limestone and cola meaning to dwell. Named for its apparent association with limestone bedrock
The taxonomy of Spongosorites is confused, mainly because the subtle differences in the spicules are hard to determine and there are few good records of external appearance. The small size of the largest oxeas separates this species from many others in the genus, in many other species these reach over 500 µm. It also lacks centrotylote oxea which are present in several species. The spicule range is similar to that of S. difficilis (Lundbeck, 1902), which has oxeas 60-370 by 4-10 µm. However, it may be distinguished from S. difficilis as this is grey when alive and undergoes a colour change to black when exposed to air, the spicules also appear more sharply pointed and style-like forms are not present. Spongosorites coralliophaga (Stephens, 1914), originally described as Cliona coralliophaga, was originally described from deep water coral reefs off the west coast of Ireland and has also been recorded from coral reefs at Rockall Bank and Mingulay, near the Hebrides, relatively close to Rathlin (van Soest, 2006). It has oxeas of a similar size-range (80-550 by 2.5-11 µm). However, these are described as tapering to long points and are bent twice in the same direction, Stephens says 'bi-angulated', whereas the majority of those in S. calcicola are only slightly curved and have rounded ends. It is also described as undergoing a colour change in alcohol whereas none is observed in S. calcicola. Furthermore, S. coralliophaga is formed of small lobes (7 mm by 5 mm), rather than being massive, and has much smaller oscules (4-5 mm diameter).
Source: Picton & Goodwin, 2007