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(Topsent, 1892a)

Species Overview

Polymastia grimaldii (Topsent, 1892a) is a disc-shaped sponge with only the barest attachment to the substrate. It bears numerous conical papillae. It is an Arctic-Boreal deep water species.

Taxonomic Description

Colour: Not known in vivo, it is whitish in alcohol.
Shape, size, surface and consistency: This species is disc-shaped and fixed only by certain points to the substrata. At the limit between the upper face and the lower face a rather long fringe of bristles may be observed. The papillae are very numerous and located on the upper face. The upper face is hispid and the lower face smooth. Size may be up to 20 cm in dameter, and such a specimen may have almost 300 papillae. Consistency firm.
Spicules: There are four different kinds of spicules. The principal and the intermediary are fusiform strongyloxea or fusiform tylostyles. Principal: 1450-2275 x 21-26 µm; intermediary: 210-676 x 10.4-21 µm; ectosomal tylostyles: 172-286 x 5.2-7.8 µm. The bristles of the edge are long and thin styles, the smallest are 2 mm long and their maximum length is greater than 4 mm x 10 µm thick.
Skeleton: (Polymastia grimaldi cross) Ectosomal: The upper cortex about 650 µm thick is composed of three layers: a layer of tangential intermediary tylostyles, 250 µm thick; a collagenous layer, 150 µm thick; on this lies the cortical layer of ectosomal tylostyles. These three layers are traversed by the bundles of principal tylostyles. At the junction between the upper and the lower faces there is a fringe of very long, thin bristles. On the lower face the two external layers of the cortex disappear and only the layer of tangential intermediary tylostyles remains. The bundles of principal tylostyles run parallel to the surface. Choanosomal: bundles of tylostyles, 100-200 µm in diameter, echinate the surface and pass through the palissade of small tylostyles. In the choanosome between the bundles, free small tylostyles are scattered. Papillae: exhalant papillae and inhalant papillae are distinct but built on the same scheme. The only difference is the thickness of their wall. From the center to the surface they are made of a central canal (inhalant or exhalant), bundles of longitudinal tylostyles, a layer of tangential tylostyles and a cortical layer of small tylostyles.
Ecology: Deep water, 70-650 m.
Distribution: This species is quite characteristic for the boreal region of the Atlantic. It is known from 65°21'N to 72°5'N / 10°42' W to 37°57' E.
Type specimen information: The type is in the Monaco Museum.

Remarks

There is a large amount of confusion in the literature between P. mamillaris (Müller, 1806), P. penicillus (Montagu, 1818) and P. grimaldi. Vosmaer (1885) described as P. mamillaris an obvious specimen of P. grimaldi. Polymastia penicillus is normally considered a synonym of what was called P. mamillaris by most authors (now: P. penicillus). Therefore part of the sponges described as P. penicillus by Vosmaer (1882b, not: Montagu, 1818), Hansen (1885), Levinsen (1886), Fristedt (1887) are also P. grimaldii. The differences between P. grimaldii and P. penicillus are absolutely clear and no confusion is possible between the two species.
This species represents an other step in the evolutionary line between Polymastia and Radiella. Polymastia grimaldii was described in 1892 as a Trichostemma (= Radiella), but Topsent preferred to consider it as a Polymastia in 1927.
Source: Boury-Esnault, 1987

Polymastia grimaldii