(Bean in Johnston, 1842)
Species Overview
Guancha lacunosa (Bean in Johnston, 1842), also known as Clathrina lacunosa , is an easily recognizable calcareous sponge because of its globular body on a thin stalk, making it resemble a balloon on a string. It is whitish in colour. It is often overlooked because of its small size. There is a second stalked similar sponge, G . blanca which differs in having no oxeas (microscopical examination).
Taxonomic Description
Colour: White, off-white.
Shape, size, surface and consistency: Stipitate, the stalk bearing a roughly ovoid (Guancha lacunosa BandW), sometimes slightly flattened, body, consisting of a network of thin walled anastomosing tubes. Maximum height 3 cm, although specimens are frequently less than half this size. Surface: in macro view, the sponge surface is even. The surfaces of the individual tubes are smooth. A single oscule (?sometimes more) lies at the apex of the sponge. Contraction not noticeable. Consistency: firm to soft; even tough and resilient.
Spicules: (Guancha lacunosa spics) Calcareous. Triactines are of two types: with rays of equal length, 80-300 µm; sagittal triactines with the basal ray (90-600 µm) longer than the two paired rays (60-300 µm). The latter paired rays may exhibit abnormalities. The diactinal spicules (oxeas) are 80-300 µm long. The growth point is normally marked by a central irregularity (Guancha lacunosa SEM spics).
Skeleton: The skeleton consists of triactines distributed throughout the body, with diactinal spicules occurring at the base of the body, and in the stalk.
Ecology: On vertical, hard surfaces. Often found attached to empty shells in sheltered conditions in sealochs. Also reported growing on hydroids and bryozoans. Littoral to 220 m. (Note: this small, inconspicuous and delicate species can be quite difficult to spot, but is fairly common. More habitat information is required).
Distribution: Around the Atlantic coasts of Europe it is known from Bretagne, Plymouth, Ramsgate, Scarborough, Berwick, St. Andrews, and Shetland. Recorded recently from Salcombe (Devon), Sound of Jura (Hebrides) Rathlin Island, Skomer and Strangford Lough. Also known from the Arctic and Mediterranean.
Etymology: The name refers to the lacunose habit.
Type specimen information: Bowerbank's specimens (Leucosolenia lacunosa Bow.) may include the original Bean specimens.
Remarks
The external form ("like a Clathrina coriacea on a stalk") is characteristic. This species was regarded by Burton (1963: 183) as being one of seven "named forms" comprising Clathrina coriacea (Montagu, 1818) which he accepted as the valid name for the whole complex. The species is now placed in the genus Guancha Miklucho Maclay, which differs from Clathrina in being stalked and having parasagittal triactines.
Sources: Ackers et al., 1992 (as Clathrina ) (editors D. Moss and B.E. Picton); Borojevic and Boury-Esnault, 1987.