(Montagu, 1818)
Species Overview
Leucosolenia complicata (Montagu, 1818) is a mass of whitish tubes which rise up or hang down from the substrate to form arborescent bushes. The tubes always have side-branches (diverticula). It is similar to Leucosolenia variabilis but that species normally does not become arborescent (it is just a thick mass of interwoven tubes) and has no or few diverticula. It is a fairly common species occurring in the shallow sublittoral along most rocky coasts of Europe.
Taxonomic Description
Colour: Off-white to grey.
Shape, size, surface and consistency: The sponge consists of a basal reticulation of thin-walled tubes which creep and anastomose over the substrate, from which arise numerous, long, free-standing, closely-set oscular tubes which are always provided with lateral diverticula, which may subdivide even further. It occurs as a bushy form and as an arborescent form. Surface of the tubes is soft and smooth; minutely hispid. The oscules are terminal on erect tubes. The oscular rim is short. Consistency very delicate and soft; very fragile. Contraction: The tubes cling together by surface tension when out of the water. Otherwise no noticeable contraction occurs.
Spicules: (Leucosolenia complicata spics) Calcareous. Triactines have paired rays 75-90 x ca. 7 µm thick and basal ray 100-200 µm long x ca. 6 µm thick. Tetractines have basal ray 100-200 µm long x ca. 6 µm thick, the other rays are 70-90 x ca.7 µm. The oxeas are of two sizes; the larger, 190-280 x 9-10 µm thick, usually have lanceolate distal ends and curved shafts; the smaller are usually abundant, without lanceolate ending, 70-140 x ca. 3 µm thick.
Skeleton: The skeleton of the chamber layer consists of triactines. The choanosomal skeleton is of tetractines, which also line the atrial cavity. Oxeas are also present.
Ecology: This sponge reaches its optimal development under overhangs on the shore, growing as compact, hanging 'bunches', often associated with the red alga Plumaria elegans . Rarely found in situations in which it is liable to be left dry at low tide. The 'bushy form' may be more typical of muddy estuarine conditions; the 'arborescent form' of clear water, free of mud and sediment? Observations would be welcome on this feature. Littoral to 93 m.
Distribution: Arctic; Atlantic coasts of Europe; Mediterranean.
Etymology: The name refers to the habit.
Type specimen information: BMNH: 1910.1.1.435Aa (2 slides), Norman Collection. "From Minchin Coll. Type".
Remarks
Superficially this species can be confused with several other species of Leucosolenia including L . botryoides , L . variabilis and Clathrina contorta .
Source: Ackers et al., 1992