Family METANIIDAE Volkmer-Ribeiro, 1986

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Introduction

Metaniidae Volkmer-Ribeiro, 1986 is a family of freshwater sponges which produce large asexual resting bodies (gemmules) with a well-developed vesicular coat of spongin. Growth forms are delicately encrusting, bulbous or tubular. Megascleres consist of two size classes of spicules: the larger ones are entirely smooth, diactinal, structural spicules, typically stout oxeas, strongyloxeas or strongyles (Hooper & Wiedenmayer 1994: figs 5, 6, 8), forming reticulate skeletal tracts, and usually enclosed within well-developed spongin fibres; the smaller ones are spined oxeas or strongyles (Hooper & Wiedenmayer 1994: fig. 137) surrounding the gemmule's vesicular coat. Microscleres include minute oxeas, with large central spines and granular spination elsewhere, and small chelae. Gemmoscleres include modified (boletiform) cladotylotes (Hooper & Wiedenmayer 1994: fig. 140).

This family inhabits Neotropical (central and eastern South America), southeast African, and the Indo-Malayan regions (Burma, Borneo), and the Northern Territory of Australia, apparently largely corresponding with the distribution of the world's rainforests (Volkmer-Ribeiro 1986). Four genera are recognised, only one of which is recorded for Australia.

The family was revised recently by Volkmer-Ribeiro (1986). There is doubt, however, whether 'chelae' seen in these sponges are homologous with those found in the Poecilosclerida. More probably, they are derivatives of amphidiscs which have become curved and relatively large, and thus convergent upon chelae morphology, as an adaptation to the structure of the gemmular walls in which they are located. Similarly, 'cladotylotes' in these freshwater sponges are probably also not homologous with those of Acarnus in the Poecilosclerida, in which case this family may be more appropriately returned to the Spongillidae (Haplosclerida).

Database Notes

2004

Now contains 5 genera instead of 1.

Diagnosis

Spongillina with body shape encrusting, massive, bulbose, globular. Surface smooth, hispid to conulose. Consistency from fragile to very hard. Ectosomal skeleton consists of tangential spicules in the dermal membrane or spicule tufts from emerging fibres. Choanosomal skeleton alveolate-reticulate irregular. Megascleres are oxeas to strongyles, from smooth to spiny. Microscleres, when present, are acanthostrongyles, acanthoxeas, asters, pseudobirotules. Gemmules subspherical to oval, with or without cage. Foramen present. Gemmular theca usually trilayered with radially arranged gemmuloscleres. Gemmuloscleres boletiform (tubelliform), parmuliform, pseudobirotules.

ID Keys

KEY TO GENERA
(1) Parmuliform spicules (gemmuloscleres) are present; squat and smooth oxeas as megascleres; microscleres are acanthoxeas ------------------------------------------------------------------------------------------------------------- Drulia
Absence of parmuliform spicules (gemmuloscleres) ------------------------------------------------------------------------ 2

(2) Tubelliform spicules (gemmuloscleres) are present -------------------------------------------------------------------- 3
Absence of tubelliform spicules as gemmuloscleres ------------------------------------------------------------------------ 4

(3) Gemmuloscleres show a single tubelliform morphology, radially arranged with the larger rotule embedded in the inner layer of the gemmular theca; microscleres are strongyles from smooth to spiny; megascleres are oxeas and strongyles, smooth and spiny ---------------------------------------------------------------------------------------- Metania
Gemmuloscleres of two different morphs: rare tubelliform, arranged radially on the gemmular theca around the foramen; and pseudobirotules radially arranged inside the gemmular theca; microscleres are absent; megascleres are few smooth oxeas and abundant smooth or microspined strongyles----------------------------------------- Acalle

(4) Gemmuloscleres are pseudobirotules with a long slim smooth shaft radially arranged; megascleres are long fusiform oxeas showing rare spines or tubercles; microscleres are pseudobirotules with a short smooth shaft -------------------------------------------------------------------------------------------------------------------- Corvomeyenia
Gemmuloscleres are birotules with a short shaft embedded radially inside the gemmular theca; megascleres are acanthostrongyles associated with spiny and smooth oxeas; microscleres are acanthostrongyles and acanthoxeas and exclusive ‘aster-like’ spicules showing many rays-------------------------------------------------------- Houssayella

Diagnosis References

Manconi, R. & Pronzato, R. 2002. Suborder Spongillina subord. nov.: Freshwater sponges. pp. 921-1020 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. [985]

General References

Volkmer-Ribeiro, C. 1986. Evolutionary study of freshwater sponge genus Metania Gray, 1867: III. Metaniidae, new family. Amazoniana 9(4): 493-509

History of changes