Acanthascus (Staurocalyptus) roeperi (Schulze, 1887)
Shape and size: cup-shaped body, 16 cm in length and 95 cm in maximum breadth. The solid inferior portion of the sponge is contracted into a cylindrical stalk, 2.5 cm in thickness. This stalk is bent to the side, as if to be attached to some solid body, but the rest has been unfortunately torn away. The somewhat bulging wall of the cup has a thickness of 8 mm at the lower part, but decreases gradually towards the upper margin, and ends in a simple smooth margin, bent slightly outwards. The sharp, uniform, circular edge exhibits no projecting marginalia.
Besides this large specimen a small, flat, wide cup- or basin-like form was obtained at the same locality. It measured 2 cm in maximum breadth and 1 cm in height, but was also torn away from its connection, and exhibited only a torn base, 1.5 cm in breadth. From this the side wall of the body, measuring about 2 m. in thickness, arises, projecting obliquely upwards and outwards, and continued on to a smooth, circular, sharp edged margin, measuring 2 cm. in diameter. In perpendicular cross sections through the wall of the cup one can readily detect the alternating afferent and efferent canals, and the folds of the chamber layer which extends between them.
Surface: Through the thin even lattice-work of the dermal membrane are seen the irregularly scattered, elongated, angular or spindle-shaped pits, from which roundish canals extend towards the centre. On the inner surface round sharply contoured depressions of various sizes occur, into the bottom of which the more or less wide excurrent canals of the efferent system open.
Skeletal elements: The main portion of the parenchymal skeleton consists of long slender diacts with rough pointed or slightly club-shaped ends, with or without central nodes, like those which have been already so often described in this family. There is an isolated occurrence of small, weakly-developed oxyhexacts with fine straight rays, and a greater abundance of oxyhexasters with short, sometimes very short, principal rays, bearing long, diverging, straight or wavy, fine terminals. The number of terminals on each principal ray varies from two to three, while less frequently only one is present. Not unfrequently the principal rays are so short that they can hardly be detected, being hidden by a spherical central thickening, from which the long terminals directly arise, resulting in a many-rayed form.
In certain regions, and especially below the external skin, in the subdermal space, there is a tolerably abundant occurrence of those eight-rayed discohexasters, which were already described in Acanthascus (Rhabdocalyptus) mollis. Here also there are eight medium-sized principals not exactly round, but somewhat angular. These form approximately equal angles with the central node, which is beset with roundish tubercles. Terminally the principals divide into three to four fine, long, diverging terminals, which bear on their extremities small, toothed, transverse discs. We have also to note the quite isolated occurrence of very small delicate discohexasters, in which the expanded ends of the principal rays bear numerous fine terminals, with transverse discs on their extremities.
The dermal skeleton includes medium-sized hypodermal oxypentacts, in which the long, smooth, occasionally somewhat curved rays, are roughened towards the pointed extremities. The dermal membrane itself contains a large number of pentacts, tetracts, diacts, and occasionally monacts, in which the rough straight rays, beset with small pointed spines, are rounded off at their outer ends, or provided with blunt points. At the middle of the djacts and at one end of the monacts, four or five cruciately disposed hemispherical tubercles (or sometimes two in one axis) project laterally as rudiments of the undeveloped rays.
The gastral skeleton, and that of the skin which lines the wide efferent canals, consists exclusively of comparatively large oxyhexasters in the usual disposition. The weakly developed straight rays, which are of approximately equal length, have an irregularly tubercled or roughened surface. There are no marginalia in this species.
Synonymised taxa : Acanthascus roeperi (Schulze, 1887) (subgenus assignment)
Rhabdocalyptus roeperi Schulze, 1887 (genus transfer)
Ecology and Distribution
Links and Resources
World Porifera Database : http://www.marinespecies.org/porifera/porifera.php?p=taxdetails&id=172003