Topsent, 1928
Definition: Main skeleton is partially or entirely composed of an isodictyal anisotropic or isotropic, occasionally alveolate reticulation of spongin fibres and/or spicules, with uni- to multispicular tracts of diactinal spicules forming triangular, rectangular or polygonal meshes. Megascleres are exclusively oxeote or strongylote, bonded together with collagenous spongin or enclosed within spongin fibres; microscleres, if present, may include sigmas and/or smooth toxas (both frequently centrangulate), or microxeas.
Remarks: The oxeas in this order are very often of the kind dubbed "# oxea abruptly-pointed", subtly but recognizably distinct from oxeas in other orders.
Nine families of sponges are included here, six of which are viviparous (Chalinidae, Niphatidae, Callyspongiidae, Spongillidae, Metaniidae and Potamolepidae), with parenchymella larva bearing various patterns of ciliation, two oviparous groups (Petrosiidae and Phloeodictyidae), and one uncertain (Lubomirskiidae). All four families of freshwater sponges are included in this order (Spongillidae, Lubomirskiidae, Metaniidae and Potamolepidae). Haplosclerids are probably the most abundant and diverse of all tropical sponges, and they are also relatively common in other areas.
A recent controversy was raised by Bergquist (1980) who proposed to subdivide the order into two distinct (and unrelated) orders, viz. Haplosclerida s.s. and Nepheliospongida (later also dubbed Petrosida). The first supposedly incubated their larvae, the second was oviparous; the second group would have unique chemistry. Subsequent studies have failed to substantiate the chemical distinctness of the Nepheliospongida, and other chemical characters (notably 3-alkyl piperidine derivatives, cf. Andersen et al., 1996 and straight-chain acetylenes, cf. Van Soest et al., 1998) have been found to occur over both groups, re-establishing their integrity.
Revisions: Griessinger (1971), Bergquist and Warne (1980), Van Soest (1980),
Desqueyroux-Faundez (1984, 1987), de Weerdt (1985, 1987), Fromont (1991, 1992).
Source: Hooper's Internet Sponge Guide.
The following families are represented in the area:
Family Chalinidae: simple skeletons with primary lines/tracts/fibres at one or rarely two spicules distant from one another; ectosomal skeleton if present a single spicule reticulation with spicules touching at the nodes (H. magnifica ectosome) (Haliclona curacaoensis skel).
Family Niphatidae: thick tracts or fibres lying several at distances of spicules from each other; ectosomal skeleton a reticulation of spicule tracts or fibres, forming rounded meshes, often paratangentially.
Family Petrosiidae: skeletal tracts forming isotropic, often even alveolar, meshes; consistency hard; ectosomal skeleton consists of single spicules intercrossing (Petrosia crassa drawings).
Family Phloeodictyidae: single spicule reticulation strengthened by directionless thick spicule tracts; ectosomal skeleton crust-like (Oceanapia robusta draw).