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(Lamarck, 1814)

Species Overview

Polymastia boletiformis (Lamarck, 1814) (also known as P. robusta Bowerbank, 1861) is a brightly coloured orange-yellow fistulose sponge with a thick, massive base. The closed (inhalant) fistules have pointed ends and they collapse when put into alcohol. The surface is smooth, velvety. Colour, fistule shape and smoothness differentiate it from the other common Western European Polymastia, P. penicillus.

Taxonomic Description

Colour: Varying shades of orange or yellow, depending on density. The body and papillae are similar.
Shape, size, surface and consistency: (Polymastia robusta Bow) (polymastia_bolet_mcs2.jpg) (polymastia_bolet_draw.jpg) (polymastia_bolet_detail.jpg) Massive—globose, with a mean volume of 40 cm3. A thick, bulbous sponge, with the upper surface covered by vertical, tapering (conical), contractile papillae. The hollow papillae are approximately the same length, but vary in number from individual to individual. Typically the papillae are simple, but occasionally two adjacent papillae fuse along their length, resulting in figure '8'-like oscular openings (more rarely, three papillae may fuse). The sponge is firmly attached by a broad base. The body is soft; the papillae are firm but flexible. Surface clean, smooth and slightly velvety. The surfaces of the body and the papillae are similar. The oscules and pores are carried on conical papillae. There are usually a few papillae with terminal oscules gaping wide open. Pores cover the surface of the papillae and are visible in situ, but become invisible on collection. The body contracts slightly when collected and preserved. The papillae are contractile, and may reduce to small button-like bumps over the surface of the body. Rarely, papillae may collapse to lie fully extended over the surface, resembling floppy straps. This is a condition typical of preserved specimens, but can occur when an individual is stressed. Confirmation is needed. The oscules can be induced to close slowly when touched. Slime: None.
Spicules: The megascleres are tylostyles of two size groups: the spicules of the choanosomal tracts and the tangential layer: 250-700 x 8-15 µm [mean value about 400 µm, n= 500 (Boury-Esnault, 1974)]; the spicules of the surface brushes: 90-230 µm [mean ca. 150 µm, n=500 (Boury-Esnault, 1974)].
Skeleton: (polymastia_bolet_skel.jpg) Radiate to sub-radiate, with the radial arrangement being most apparent near to the surface, where there is a well organised ectosome. The ectosomal region has a thickness of 700 µm, consisting of a perpendicular layer of 250 µm in thickness and a tangential layer underneath of 450 µm in thickness. The perpendicular layer is a single layer of smaller tylostyles. These are arranged perpendicular to the surface, grouped into plumose brushes, but becoming more tightly packed in mature sponges to form a palisade. The tangential layer contains scattered spicules. Choanosome: the larger main structural megascleres form loose, multispicular tracts (10-12 spicules thick), which wander up through the body and on into the papillae, but do not pierce the surface. Loose spicules lie scattered between the tracts. The inhalant and exhalant canal systems fill the centres of the papillae, supported by the multispicular tracts. Inhalant canals vary from 3 to 12 in each papilla and they are distributed around a single exhalant canal. Longitidinal multispicular tracts number 10 to 30 in each papilla, each bundle being 5 to 20 spicules in thickness. At the surface of the papillae, the ectosomal skeleton is exactly as that of the body.
Reproduction: September (Borojevic, 1967)
Ecology: Most commonly found on sediment covered, upward facing rock or boulder tops on the bottom plain, associated with a bryozoan/hydroid turf. Found in conditions varying from quite rapidly flowing water to those in which silt falls out of suspension. Depth range: From tidal pools to 2300 m, common from 15 m downwards.
Distribution: Arctic; Atlantic coasts of Europe and North America; Mediterranean; known from many sites on the western and southern coasts of the British Isles.
Etymology: This species is generally thicker, more robust than other Polymastia.
Type specimen information: The type is in the Natural History Museum, London.

Remarks

The other common, papillate sponges in British waters which might be confused with P. boletiformis by appearance are Ciocalypta penicillus and P. penicillus. Apart from other differences (see table under P. penicillus), P. boletiformis sits proud on the rock surface, whereas P. penicillus often occupies small, shallow hollows.
In the recent literature this species is consistently named P. robusta (Bowerbank, 1861). However, Topsent (1933) in his revision of Lamarck's sponges, discovered that a Lamarck specimen labeled Alcyonium boletiforme conformed to Polymastia robusta Bowerbank.
Polymastia radiosa Bowerbank (1866) is here considered a synonym of the present species (in accordance with Boury-Esnault, 1987); however, recently she (Boury-Esnault et al., 1994) changed her mind and considered this a valid species occurring in deep water.

Comparison with P. penicillus: p_penicillus__p_robusta.jpg (=P. boletiformis)
Sources: Ackers et al., 1985, 1992; Boury-Esnault, 1987

Polymastia boletiformis