Family ACARNIDAE Dendy, 1922

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Introduction

Defined as encrusting, massive, flabellate or digitate growth forms, sometimes burrowing and fistulose; ectosomal skeleton forming tangential tracts of tylotes or strongyles with microspined bases; choanosomal styles form reticulate (in massive) or plumose skeletons (in encrusting growth forms); echinating spicules present or absent; microscleres include palmate isochelae and toxas (both sometimes lost), occasionally also with other microscleres such as bipocillae, modified anisochelae, microrhabds and raphides.

Thirty two nominal genera are included here, although only 17 of these are presently considered to be valid.

Shapes in this microcionine family are varied (fistular, encrusting, lobate, branching, vase-shaped). The spiculation includes those typical of the suborder: smmooth or spined styles, palmate chelas and toxas (although these are absent in Iophon and Acanthorhabdus);sigmas are absent. Skeletal architecture in non-fistularforms is variously anisotropic, plumose, or isotropic.

This concept of a revived family was first introduced by Hajdu et al. (1994) and elaborated by Van Soest et al. (1994). The following fistular genera conform to it: Cornulum, Paracornulum, Zyzza, Acheliderma, Damiria, Melonchela, Anisotylacanthaea and Xytopsene. These genera were previously united in the subfamily Cornulinae Lévi & Lévi (1983). In addition, four non-fistular genera considered to belong in this family, viz. Iophon, Acarnus, Megeciella, and Acanthorhabdus (Desqueyroux-Faundez & Van Soest, 1996). A detailed revision of the family is in progress (Hooper, in prep.), and from preliminary re-examination of type material it is possible, although not yet corroborated, that Microtylotella should be merged in Acarnus and Tedaniophorbas should be synonymised in Megaciella.

Family reviews are in Berquist & Fromont (1988), Desqueyroux-Faundez & Van Soest (1995). Recent reviews of individual families or the genera include those of Van Soest (1984), Hooper (1987), Van Soest et al. (1991), Hiemstra & Hooper (1991),Van Soest, Zea & Kielman (1994), Hooper & Krasochin (1989).

Diagnosis

Encrusting, massive, flabellate or digitate growth forms, sometimesburrowing, many genera producing fistules. Ectosomal skeleton composed of tylotes, strongyles or modified tylote spicules bearing microspine bases forming tangential and/or paratangential tracts, often irregular or halichondroid in arrangement. Choanosomal megascleres are styles or modified styles (anisoxeas) forming reticulate structures in massive forms (isodictyal, isotropic, anisotropic or more irregular skeletons) or plumose or hymedesmioid skeletons in encrusting growth forms. Echinating spicules present or absent, consisting of acanthostyles and/or unique cladotylotes. Microscleres include palmate isochelae and toxas of various morphologies (both sometimes lost), with some genera also having other microscleres such as bipocillae, modified anisochelae, microrhabd-like spicules (modified microxeas or microstrongyles) and diamond-shaped microxeas (modified toxas).

ID Keys

KEY TO GENERA
(1) Ectosomal spicules are tylotes, mostly smooth, with apical spines ---------------------------------------------------- 3
Ectosomal spicules modified ----------------------------------------------------------------------------------------------------- 2

(2) Ectosomal tylotes modified to acanthoxeas with apical spines -------------------- Acanthorhabdus (non-fistular)
Ectosomal tylotes entirely smooth (secondary loss of spines) ------------------------- Tedaniophorbas (non-fistular)

(3) Choanosomal skeletal structure well-formed ------------------------------------------------------------------------------ 4
Choanosomal skeletal structure vestigial, consisting of single tylotes and scattered accessory spicules
(acanthoxeas) --------------------------------------------------------------------------------------------- Cornulella (fistular)
(4) Choanosomal and ectosomal megascleres clearly differentiated in geometry and distribution -------------------- 6
Ectosomal tylotes form both ectosomal and choanosomal skeletal structures ------------------------------------------- 5

(5) Apically-spined tylotes form both tangential ectosomal and plumo-reticulate choanosomal skeletons
(with or without a second category of choanosomal styles) ----------------------------------------- Cornulum (fistular)
Apically-spined tylotes form both tangential ectosomal tracts and plumose ascending choanosomal tracts
(with acanthostyles echinating hymedesmioid basal skeleton) --------------------------------- Paracornulum (fistular)
Apically-spined tylotes are the only megascleres --------------------------------------------------------- Damiria (fistular)

(6) Choanosomal megascleres consist only of styles, without accessory spicules ---------------------------------------- 8
More than one category of choanosomal megascleres, one greatly modified --------------------------------------------- 7

(7) Accessory spicules consist of verticillately-spined strongyles (or strongyloxeas) ----------------- Zyzzya (fistular)
Accessory spicules consist of one or more classes of cladotylotes ------------------------------- Acarnus (non-fistular)
Accessory spicules consist of peculiar acanthostrongyles with numerous spined cladi’ ----------------------------------------------------------------------------------------------- Dolichacantha (non-fistular)
Accessory spicules consist of ‘plocamiform’ acanthostrongyles echinating ascending tracts of styles ------------------------------------------------------------------------------------------------------------ Wigginsia (non-fistular)

(8) With a regular, uni- or pauci-spicular isodictyal choanosomal reticulation of smooth or spined styles,
with or without echinating acanthostyles -------------------------------------------------------------- Iophon (non-fistular)
With confused choanosomal skeleton divided into primary ascending multispicular tracts and secondary interconnecting uni- or bispicular tracts, both cored by basally spined styles, with or without echinating acanthostyles ---------------------------------------------------------------------------------------- Megaciella (non-fistular)
Choanosomal skeleton appears predominantly plumose due to the dominance of subectosomal tracts of ectosomal tylotes, whereas the basal choanosomal skeleton is irregularly renieroid-reticulate composed of basally spined styles forming triangular or square meshes; microscleres include elongated diamond-shaped microxeas ------------------------------------------------------------------------------------------------------------ Acheliderma (fistular)

Diagnosis References

Hooper, J.N.A. 2002. Family Acarnidae Dendy, 1922. pp. 412-431 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. [412]

General References

Bergquist, P.R. & Fromont, J. 1988. The marine fauna of New Zealand: Porifera, Demospongiae, Part 4 (Poecilosclerida). New Zealand Oceanographic Institute Memoir 96: 1-197 pls 1-57

Desqueyroux-Faundez, R. & van Soest, R.W.M. 1996. A review of Iophonidae, Myxillidae and Tedaniidae occurring in the South East Pacific (Porifera: Poecilosclerida). Revue Suisse de Zoologie 103: 3-79

Hiemstra, F. & Hooper, J.N.A. 1991. Additions to the Indo-Australian representatives of Acarnus Gray (Porifera: Demospongiae: Poecilosclerida), with description of a new species. Memoirs of the Queensland Museum 30(3): 433-442

Hooper, J.N.A. 1987. New records of Acarnus Gray (Porifera: Demospongiae: Poecilosclerida) from Australia, with a synopsis of the genus. Memoirs of the Queensland Museum 25(1): 71-105

Hooper, J.N.A. & Krasochin, V.B. 1989. Redescription of the burrowing sponge Zyzzya massalis (Dendy) from the Seychelles and Houtman-Abrolhos Islands. The Beagle, Records of the Museums and Art Galleries of the Northern Territory 6(1): 133-140

Van Soest, R.W.M. 1984. Deficient Merlia normani Kirkpatrick, 1908, from the Curaçao Reefs, with a discussion of the phylogenetic interpretation of Sclerosponges. Bijdragen tot de Dierkunde 53(2): 211-219

Van Soest, R.W.M. 1984. Marine Sponges from Curaçao and other Caribbean Localities. Part III. Poecilosclerida. Studies on the Fauna of Curaçao and other Caribbean Islands 66(199): 1-167

Van Soest, R.W.M., Zea, S., Kielman, M. 1994. New species of Zyzza, Cornulella and Damiria (Porifera: Poecilosclerida), with a review of fistular genera of Lophonidae. Bijdragen tot de Dierkunde 64(3): 163-192

History of changes