Family PETROSIIDAE Van Soest, 1980

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Introduction

Petrosiidae Van Soest, 1980 are typically massive, vase-shaped or volcano-shaped sponges, or sometimes have encrusting, bulbous, and less commonly, branching growth forms. The sponge texture is characteristically stony, brittle, reflecting that in most species siliceous spicules are clearly dominant over spongin. The ectosomal skeleton is an isotropic reticulation of single spicules or spicule tracts forming a crust and giving the surface a smooth appearance; megascleres are oxeas, strongyloxeas, and strongyles (Hooper & Wiedenmayer 1994: figs 5, 6, 8), and may include smaller sausage-shaperd strongyles in one genus. The choanosomal skeleton is more or less a regular isotropic reticulation of multispicular tracts, without distinction between primary or secondary tracts, bound together with minimal spongin, forming oval meshes. Microscleres may include microxeas (Hooper & Wiedenmayer 1994: fig. 105) and microstrongyles (Hooper & Wiedenmayer 1994: fig. 106). Reproduction is oviparous.

These sponges are widely distributed in shallow waters, especially in tropical and warm-temperate regions, living at depths reaching at least 185 m (Hartman 1982). Four genera are recognised, although only three are well established; three of these genera are represented in the Australian fauna. The fourth, Strongylophora, is also known from unpublished collections from northern Australia (Hooper, unpublished data).

This family has been included in the Haplosclerida by some authors (e.g. Van Soest 1980) or retained in a separate order Petrosida by others (e.g. Hartman 1982), as the 'stony' sponges—an enclave of oviparous species amongst the viviparous haplosclerids. Petrosids also apparently differ from the Haplosclerida in that some species have unique sterols with a cyclopropene ring in a side chain (Bergquist 1980a). However, there is still debate as to the level of taxonomic divergence between the petrosids and the haplosclerids. Whilst recognising the utility of ordinal recognition of the group, we maintain it within the Haplosclerida on a provisional basis. The ordinal name Petrosida is now used more widely instead of Nepheliospongida, as it is considered by Hartman (1982) and others that the resemblance between the Recent petrosids and the fossil nepheliospongids is probably not as close as originally proposed by Wiedenmayer (1977).

Hartman (1982) reviewed the family (in the order Petrosida).

Database Notes

2004

Now contains 1 new genus and 2 new sub-genera.

Diagnosis

Diagnosis (emended from Van Soest 1980; Hooper &
Wiedenmayer 1994)
Massive, volcano or vase-shaped, bulbous and less commonly, encrusting-branching sponges. Sponge texture characteristically stony and brittle due the high silica content of the mineral skeleton, about 58% relative to spongin content of the skeleton (Desqueyroux-Faúndez 1987). Surface smooth, covered by a smooth, strong crust or variably hispid. Specialised ectosomal skeleton consisting of an isotropic tangential reticulation of free spicules or spicule tracts, forming the mineral crust. Choanosomal skeleton is a more-or-less regular isotropic network of multispicular tracts where primary and secondary fibres are indistinct. Spongin not visible, spicules bound together with the minimal amount of spongin. Multispicular tracts are regularly distributed to form, rounded meshes parallel to the surface, that can be ill defined or masked by the abundant free spicules. Megascleres: oxeas to strongylotes. Microscleres if present, smaller oxeas. In one subgenus (Strongylophora), smaller, sausage-shaped strongyles exist. Spicule types and size classes are very variable within different genera, ranging from only one type of spicule in only one size class, smaller than 200um long (Neopetrosia) or larger than 200um long (Xestospongia), up to two types of spicules with five size classes (Strongylophora). Spicule morphologies and sizes are considered important taxonomic characters among different genera, since they are fixed and stable for each genus (Table 1). Oviparous reproduction is known for only one genus (Xestospongia), which isgonochoric and has synchronous spawning (e.g., Fromont 1988), but larvae are unknown (Bergquist 1980a).

ID Keys

KEY TO GENERA AND SUBGENERA
(1) Ectosomal skeleton clearly different from choanosomal skeleton, very dense, tangential unispicular network, finely hispid, with rounded, regular or isodictyal, or irregular, subrectangular meshes. Choanosomal spicule tracts compact, differentiated or not in primary and connecting tracts. With or without microscleres ------------------ 2, 3
Ectosomal skeleton undifferentiated from choanosomal skeleton, consisting of a very dense disordered network of free spicules, with a single type of spicule of a single size class larger than 200um long. Choanosomal skeleton consisting of short longitudinal, undivided, pauci- to multispicular tracts connected by few oxeas, causing irregular meshes ---------------------------------------------------------------------------------------------------------- Xestospongia

(2) Ectosomal skeleton finely hispid, consisting of a tangential network with rounded regular meshes and free spicules. Choanosomal spicule tracts compact, not differentiated into primary or connecting tracts. Megascleres are oxeas, ranging from oxeote to strongylote of at least three size classes, large 180–400X10–14um, medium 40–130X5–10um, and small curved strongyles 30–100X2–3um --------------------------- Petrosia (Petrosia) --- 3
Ectosomal skeleton a finely hispid, tangential network with isodictyal meshes of single spicules and free spicules at the nodal points. A second subectosomal tangential network is present. Choanosomal skeleton with irregular paucispicular tracts differentiated into short connecting and longer longitudinal tracts. Megascleres oxeas in a single size class smaller than 200um long ----------------------------------------------------------------------------- Neopetrosia

(3) Ectosomal skeleton finely shaggy, with a tangential network of multispicular tracts of strongyles and free oxeas, with ovoid to subrectangular meshes. Choanosomal spicule skeleton compact, differentiated into multispicular longitudinal tracts and interconnecting confused tracts of single strongyles. Spicules: strongyles and thin oxeas of similar length (100–120um up to 170um, but of different diameter: 5–12 and 2–4um, respectively). Microscleres absent --------------------------------------------------------------------------------------------- Acanthostrongylophora
Ectosomal skeleton a dense, granular, tangential network of single strongyles forming a subrectangular mesh, with free strongyles grouped at the nodes of the network. Abundant abruptly curved microxeas. Choanosomal spicule tracts slightly differentiated with stout longitudinal tracts and connecting short, irregular tracts of strongyles and free strongyles -------------------------------------------------------------------------------- Petrosia (Strongylophora)

Diagnosis References

Desqueyroux-Faundez, R. & Valentine, C. 2002. Family Petrosiidae Van Soest, 1980. pp. 906-917 in Hooper, J.N.A. & van Soest, R.W.M. (eds). Systema Porifera: A guide to the classification of sponges. New York : Kluwer Academic/Plenum Publishers Vol. 1. [906]

General References

Bergquist, P.R. 1980. The ordinal and subclass classification of the Demospongiae (Porifera), appraisal of the present arrangement, and proposal of a new order. New Zealand Journal of Zoology 7: 1-6

Fromont, J. 1995. Haplosclerida and Petrosida (Porifera: Demospongiae) from the New Caledonia Lagoon. Invertebrate Taxonomy 9: 149-180

Hartman, W.D. 1982. Porifera. pp. 640-666 in Parker, S.P. (ed.). Synopsis and Classification of Living Organisms. New York : McGraw-Hill Vol. 1.

van Soest, R.W.M. 1980. Marine sponges from Curaçao and other Caribbean localities. Part II. Haplosclerida. Studies on the Fauna of Curaçao and other Caribbean Islands 62(191): 1-173 49 figs 18 pls

Wiedenmayer, F. 1977. The Nepheliospongiidae Clarke 1900 (Demospongiae, Upper Devonian to Recent), an ultraconservative, chiefly shallow-marine sponge family. Eclogae Geologicae Helvetiae 70(3): 885-918

History of changes