(Keller, 1880)
Species Overview
Aaptos papillata (Keller, 1880) is a reddish-violet hemispherical or cushion-shaped sponge buried in sandy substrate with numerous conical papillae sticking out from under the sand. The tips of the papillae are lighter coloured. The consistency is firm. A rare Mediterranean species reported from the west coast of France and Portugal.
Taxonomic Description
Colour: Reddish violet, but the papillae tips are lighter; internally it is orange.
Shape, size, surface and consistency: Specimens are buried in the sand, detectable only by the papillae sticking out. The specimens exhibit two distinct shapes, the smaller ones are hemispherical and up to 2.3 cm in thickness; the others are cushion-shaped, measuring 6.5-10.5 x 3.5-8.8 x 1.3-2.5 cm; a larger specimen of 25 x 20 cm was also observed. The surface shows numerous closed conico-cylindrical papillae, height 1-6 mm, thickness 1-2.5 mm; and also some oscular, conical and bigger ones, height 2-6 mm, basal diameter 4-6 mm. The surface feels slightly hispid. The consistency is firm, difficult to tear off the substrate.
Spicules: Strongyloxeas, styles and tylostyles (Aaptos papillata spics). Strongyloxeas long, fusiform, straight, with a stair-stepped, blunt point: 513-2989 x 12-52 µm. Styles, smaller, thinner, straight, may be rare: 176-1478 x 2.5-14.5 µm. Tylostyles, intermediate in size, but mostly curved: 110-952 x 3-26.5 µm.
Skeleton: Radiating bundles of strongyloxeas (Aaptos papillata skeleton). At the surface the smaller styles and tylostyles are interspersed among the strongyloxeas to form a dense palisade. The skeleton of the papillae is similar to that of the main body: the bundles of strongyloxeas follow an axial course and diverge towards the surface.
Ecology: Found buried in the sand at low tide in the upper infralittoral zone, on rocky-horizontal surfaces.
Distribution: South coast of Brittany, west coast of Portugal; Gulf of Naples.
Etymology: The name refers to the habit.
Type specimen information: No data. Keller's material supposedly is in the Berlin Museum. No type material in BMNH.
Remarks
Aaptos papillata is distinguished from Aaptos aaptos on external features: existence of more and bigger papillae and red colour, and on spicular characters: it has tylostyles in addition to the styles/strongyloxeas. This was for the first time noted by Topsent (1925), who gave an additional difference: A . papillata would be spherical, but such a morphology is not consistently found in specimens from Portugal and France.
Descatoire (1966) described from the Iles des Glénans, south Brittany, a new Polymastia , P . gleneni , which was found to be identical to A . papillata by Lopes (1989). Polymastia have three sizes of tylostyles, including the main structural spicules, and a particular ectosomal skeletal arrangement, not found in "P ." gleneni , nor in Aaptos .
Lopes (1989), following Topsent (1925) also claimed that a specimen from Barbados in the Caribbean was attributable to A . papillata , but that seems unlikely and needs to be further substantiated.
Source: Lopes, 1989.