Merejkowsky, 1879
Defintion: Encrusting, massive, lobate, lamellate and erect columnar growth forms. Choanosomal fibre skeleton, where present, is completely dendritic and sometimes supplemented by spongin spicules, which are not attached to the primary skeleton. In massive species these fibres always arises from a flat basal spongin plate. In one genus that lacks spongin fibres the ectosome is reinforced with collagenous fibrils. Fibres have laminated bark surrounding the central pith; the pith is usually well developed but in one genus it is replaced by detritus. Choanocyte chambers are eurypylous. (Aplysilla cross section) (Darwinella rosacea)
Remarks: Eight nominal genera and six probably valid genera are included in the family. Reviews: Bergquist (1980, 1996).
Source: Hooper's Internet Sponge Guide.
Genera represented in the area:
Aplysilla Schulze, 1878 (type species: Aplysilla rosea Barrois, 1876) (syn. Simplicella Merejkowsky, 1879): always encrusting growth form; often bright yellows, reds, pink colours, with colour changes; numerous short, almost unbranched fibres; fibres always clear of detritus.
Chelonaplysilla de Laubenfels, 1948 (type species: Aplysina noevus Carter, 1876): separable ectosomal (cortical) skeleton with a delicate reticulation of sand grains; fibre structure is similar to Aplysilla but in some erect and branching species the supporting skeleton becomes more branched.
Darwinella Müller, 1865 (type species: Darwinia muelleri Schultze, 1865) (syn. Darwinia Schultze, 1865): small, encrusting, massive or lobate sponges; slightly ramified dendritic fibre skeleton is supplemented by diactinal, triactinal or quadriradiate spongin spicules; fibres lack any detritus.
Hexadella Topsent, 1896 (type species Hexadella racovitzae Topsent, 1896): encrusting growth forms; no fibres or spongin spicules; ectosome is collagen reinforced to form a noticeable skin which, acting in some measure as an external skeleton, allowing the sponge to attain a thickness up to 5 mm.
Pleraplysilla Topsent, 1905 (type species: Spongelia spinifera Schulze, 1878): with simple fibres, sometimes branched only once or twice but in thicker specimens branching more frequently; all fibres arenaceous, with an axial core of sand grains, with constant diameter from base to surface of the sponge even though the stratified bark elements diminish.
Psammopemma Marshall, 1880 (type species P . densum Marshall, 1880): the skeleton consists entirely of sand grains arranged in thick columns, rising from the substrate; these are irregularly are sparingly connected by thin sand "fibres"; the interior is often completely filled with sand grains; no visible spongin; sSurface skeleton a more or less continuous layer of fine sand grains (the genus is considered a junior synonym of the Poecilosclerid genus Psammoclema Marshall, 1880 by Wiedenmayer, 1989).
Species included:
Aplysilla rosea
Chelonaplysilla noevus
Darwinella corneostellata
Darwinella intermedia
Hexadella racovitzai
Pleraplysilla minchini
Psammopemma finmarchicum
Species not treated here:
Chelonaplysilla arenosa (Topsent, 1905), Iceland, deep water
Chelonaplysilla psammophila (Topsent, 1928), Sweden, deep water