Australian Halichondriidae (Porifera: Demospongiae): I. Species from the Beagle Gulf.

AUSTRALIAN HALICHONDRIIDAE (PORIFERA: DEMOSPONGIAE): I. SPECIES FROM THE BEAGLE GULF. JOHN N.A. HOOPER, STEPHEN D. COOK, LISA J. HOBBS AND JOHN A. KENNEDY

Queensland Museum, PO Box 3300, South Brisbane, Qld 4101, Australia.

ABSTRACT Twenty species of sponge in seven genera of the family Halichondriidae (order Halichondrida) are described from the Beagle Gulf, Darwin region, Northern Territory, including eight new species and five new records for Australia. A resume is provided of generic characters and a survey of the known Indo-west Pacific species in these genera. Porifera, Demospongiae, Halichondriidae, Axinyssa, Myrmekioderma, Topsentia, Ciocalypta, Amorphinopsis, Halichondria, Hymeniacidon, taxonomy, new KEYWORDS:

species, northwest Australia.

subsequently included in the order (Halichondriidae, Axinellidae, Dictyonellidae and Desmoxyidae), although there is not yet complete agreement about the generic composition of each of these (see Hooper and Levi 1993b). In its initial conception, Halichondriidae contained 27 very disparate genera allegedly related to each other by their possession of "fusiform or pin-shaped spicules variously fasciculated together" (Gray 1867: 503). Apart from Halichondria and Ciocalypta, all the other genera included here by Gray (1867) were subsequently assigned by contemporary authors to Poecilosclerida, Hadromerida or Haplosclerida. Nevertheless, the family name remains valid for the current assemblage of genera containing the genus Halichondria (Article 40 ICZN; Anon. 1985). Few subsequent authors used the family name Halichondriidae until it was redefined by de Laubenfels (1936) in a contemporary classification, after which time it came into general acceptance (e.g. Levi 1973; Berquist 1978; Hartman 1982). De Laubenfels' (1936: 133) interpretation of the family included eight genera, of which several were clear synonyms, all with "exceedingly simple spiculation ... of ... only oxeas ... smooth ... without microscleres ... [with] special dermal skeletons, although these are not conspicuous" (i.e. it specifically excluded sponges like Hymeniacidon with principal styles rath-

INTRODUCTION Of the 114 families of extant Porifera only two (Raspailiidae and Microcionidae, order Poecilosclerida) can so far be considered well known in the Australian fauna (Hooper 1991, 1996). In this present work we deal with a third family, Halichondriidae, in the order Halichondrida. Traditional definitions of Halichondrida were based on the possession of diactinal megascleres, a relatively homogenous skeletal structure described as `halichondroid' (criss-cross reticulate), viviparous reproduction and completely ciliated larvae (Bergquist 1978; Hartman 1982). Under this interpretation two families were differentiated, Halichondriidae Vosmaer, 1887 (principal megascleres oxeas sometimes also with accessory styles), and Hymenacidonidae de Laubenfels, 1934 (principal megascleres styles sometimes with accessory oxeas), (Bergquist 1978). A recent revision of the order by Van Soest et al. (1990) allowed for the inclusion of species with compressed axial skeletons, differentiated axial and extra-axial skeletons (i.e. traditional Axinellidae), an indiscriminate occurrence of styles and oxeas within the skeletons, as well as 'typical' halichondrids with skeletal arrangements of styles or oxeas in plumose to ill-defined, confused tracts. Four families were

In: Hanley, J.R., Caswell, G., Megirian, D. and Larson, H.K. (eds) Proceedings of the Sixth International Marine Biological Workshop. The marine flora and fauna of Darwin Harbour, Northern Territory, Australia. Museums and Art Galleries of the Northern Territory and the Australian Marine Sciences Association: Darwin, Australia, 1997: 1-65. 1

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collected from this region (extending from Northwest Cape, WA, to the Wessel Islands, NT; Hooper unpublished data), but so far less than 300 of these have been named in the literature (Hooper and Wiedenmayer 1994). Many species are unique to this region, with levels of endemism in some families thought to be about 70% (Hooper and Levi 1994), although for most sponge families this fauna is still poorly known. Habitats within this region are also incredibly diverse, most with at least some sponge species represented (ranging from ephemeral pockets of freshwater, large rivers, euryhaline estuaries and extensive mangroves, mud flats, fringing intertidal and subtidal rock and coral reefs, seagrass and Halimeda beds, artificial substrates, sand, coral rubble and shell-grit bottoms, deeper offshore rock reefs, submerged 'active' coral reefs, as well as pristine emergent platform and fringing coral reefs). There have been several major publications on sponges within the Beagle Gulf but prior to the present work only 71 species have been described. The earliest authenticated record of this fauna comes from material collected between 1875 and 1877 by T.J. Sturt, which was sent to Melbourne and initially described as a 'curiosity' (Barnard 1879), but subsequently identified by Carter (1879) as an endemic genus and species, Axos flabelliformis Carter (Hooper 1986a). In 1881 the British survey ship HMS Alert made extensive collections of the fauna, mostly dredging shallow waters within Darwin Harbour, Van Diemen Gulf, Dundas Strait and the Timor Sea. The sponges from this collection were described by Ridley (1884), and included 24 species, 21 named and three left uncertain, of which only 17 are currently recognisable as valid species. Nine of these species have not since been recorded elsewhere (i.e. apparent endemics). In the early 1960's a team from the Australian Museum, Sydney, led by Elizabeth Pope, travelled to Darwin, Cape Don and Port Essington to survey the intertidal marine biology of this region. This collection is the earliest comprehensive attempt to document the marine invertebrates of the northwest Australian coast (Pope 1967), from which the sponge fauna was described separately (Bergquist and Tizard 1967). These authors described 19 species of the larger, more prevalent intertidal sponges found in this region, belonging to 17 genera and with three new species. Since 1967, there have been 37 additional species in 16 genera described from the Beagle

er than oxeas and a fleshy, gelatinous consistency). De Laubenfels (1936) further characterised the family in having "subdermal cavities ... so very enormous that the dermis is merely a roof supported on slender columns ... above ... the endosome". Since its creation, 54 genera have been associated with the Halichondriidae, although the most recent revision by Van Soest et al. (1990) (with subsequent refinements by Diaz et al. (1991, 1993) and Pomponi et al. (1991)), now recognises only 12 of these (the remainder being junior synonyms or incorrect assignments): Amoyhinopsis Carter, Axinyssa Lendenfeld, Ciocalvta Bowerbank, Collocalypta Dendy, Didiscus Dendy,Epipolasi.s de Laubenfels,Halichondria Fleming, Hymeniacidon Bowerbank, Myrmekioderma Ehlers, Petromica Topsent, Spongosorites Topsent and Topsentia Berg. All these genera have a highly dense choanosomal spicule skeleton arranged in vague, directionless (halichondroid) tracts composed of spicules in confusion (Van Soest et al. 1990), with spicules being either principal oxeas or styles, sometimes also with smaller accessory styles or oxeas (i.e. including Hymeniacidonidae and some Axinellidae). The Halichondriidae now represents one of the few spicule-bearing (`nonkeratose) families of Porifera 'accessible' to contemporary systematics. So far only 28 species in eight of the 12 halichondriid genera have previous published records from Australian territorial waters (including Antarctica) (Hooper and Wiedenmayer 1994), and surprisingly only two of these came from the northwest Australian region. In the present work we describe 20 species in seven genera from the Beagle Gulf, of which five are new records for Australia and eight are new species. A second contribution describing halichondriids from other tropical Australian provinces is currently in progress (Hooper et al. in prep.).

DARWIN SPONGE FAUNA In this forum (i.e. The International Workshop on the Flora and Fauna of Darwin Harbour) it is appropriate to summarise existing knowledge on the Darwin sponge fauna of the greater region, namely the Beagle Gulf. The sponge fauna of northwest Australia is possibly the most diverse of all Australian marine provinces, with about 800 species already 2

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Gulf region (Darwin Harbour in particular), as well as from other parts of the NT and northern WA coasts, including notes on the ecology, biochemistry and/or biogeographical relationships of several species (Hooper 1984, I986a, 1986b, 1987, 1991, 1994; Hooper and Bergquist 1992; Hooper and Levi 1993a, 1993b, 1994; Hooper et al. 1990, 1991, 1992; Capon et al. 1986; Capon and MacLeod 1988; Cambie et al. 1988a, 1988b; Van Soest et al. 1991). Significantly, Darwin Harbour is the type locality for 22 of these species, most discovered originally from the East Point Aquatic Reserve. Nevertheless, this described fauna represents less than 10% of the species known to live in the Beagle Gulf, and it is anticipated that this list of published species will increase substantially over the next decade.

ate spicules not functionally localised to any particular region of skeleton. Spicules widely diverging in size in some taxa, sometimes with size differences between ectosomal and choanosomal skeletons. Skeletal structures ranging from disorganised plumoreticulate, crisscrossed "halichondroid skeleton", to distinctly compressed axis (or basal) skeleton and differentiated extra-axial (radial, plumose or plumoreticulate) skeleton. Spongin fibres usually poorly developed or absent. Ectosomal skeleton organised into tangential layer of spicules or erect spicule bundles, with minimal collagen, and large subectosomal spaces in many taxa. Microscleres raphides, microxeas, or spined microxeas with central bend in some species. Family Halichondriidae Gray

METHODS

Halichondriadae Gray, 1867: 503. Halichondriidae; Vosmaer, 1887: 336. - de Laubenfels 1936: 133; - Van Soest et al. 1990: 20. Ciocalyptidae Hentschel, 1923: 408. Spongosoritidae Topsent, 1928: 35,157. Petromicidae Topsent, 1928: 34,105. Hymeniacidonidae de Laubenfels, 1934: 13. Diagnosis. Halichondrida with choanosomal skeleton consisting of high density of spicules arranged in vague, ill-defined, directionless tracts and spicules in confusion. Ectosomal skeletons frequently detachable, often composed of spicules of different size than those in choanosome. Spicules are relatively large oxeas and/or styles, sometimes strongyloxeas or intermediate spicules

Methods of collection, preservation, histological preparation, and techniques for light microscopy and scanning electron microscopy are given elsewhere (e.g. Hooper 1991). Spicule measurements are based on 25 measurements of each category of spicule, and represented as range (and mean). Abbreviations used in the text are: AM, Australian Museum, Sydney; BMNH, The Natural History Museum, London; CCNT, Conservation Commission of the Northern Territory, Darwin; MNHN, Museum National d'Histoire Naturelle, Paris; NCI AIMS, Australian Institute of Marine Science (US National Cancer Institute collection contract, 19851991); NCI CRRF, Coral Reef Research Foundation, Chuuk State, Federated States of Micronesia (US National Cancer Institute collection contract, 1992); NT, Northern Territory; NTM, Northern Territory Museum, Darwin; QM, Queensland Museum, Brisbane; SMF, NaturMuseum and Forschungsinstitut Senckenberg, Frankfurt; WA, Western Australia; ZMB, Museum fur Naturkunde an der HumboldtUniversitat zu Berlin.

Genus Axinyssa Lendenfeld

Axinyssa Lendenfeld, 1897: 116. Pseudaxinyssa Burton, 1931: 350. Axinomimus de Laubenfels, 1936: 163. Type species. Axinyssa topsenti Lendenfeld, 1897, by monotypy. Diagnosis. Massive, subspherical, lobate or lobate-digitate growth forms, often with apical cloacal cavity and fistulose surface processes. Choanosomal skeleton collagenous (although spongin fibres poorly developed), with widely spaced spicule tracts cored by larger oxeas, largely strewn in confusion or slightly plumose, dendritic or vaguely radiating. Subectosomal skeleton more organised than choanosomal region, plumose or plumo-reticulate, with regular tracts of larger choanosomal oxeote megascleres

SYSTEMATICS

Order Halichondrida Vosmaer Halichondrida Vosmaer, 1887: 335. Diagnosis. Demospongiae with plumoreticulate skeletal architecture composed of relatively large oxeas, styles, strongyloxeas or intermedi3

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Habitat. Sponge bed, soft mud and shell-grit substrate; subtidal 18-200 m depth. Description. Massive, lobate, with lumpy appearance, approximately 55 mm diameter. Oscules large, up to 4 mm in diameter, discrete, scattered over entire surface (i.e. not confined to apex of sponge), flush with surface (i.e. without raised membraneous lip). Colour. Pale pinkish alive in air (Mansell 5RP 8/2); ectosome purple-grey in ethanol, with lighter choanosome. Texture. Firm, resilient, barely compressible; not easily broken. Surface. Irregular surface with incorporated detritus; minutely hispid, with series of small raised ridges running over surface forming minute reticulation. Cavernous subectosomal skeleton visible through transparent surface membrane. Ectosomal skeleton. Plumose bundles of larger spicules from subectosomal region protrude through collagenous layer at surface, forming brushes or singly, with sparse tangential layer of both smaller and larger spicules, lying singly or in paucispicular tracts, overlaying ascending subectosomal skeleton. Choanosomal skeleton. Confused halichondroid reticulation of multispicular tracts in deeper choanosomal region of skeleton, becoming slightly more organised towards periphery; multispicular choanosomal skeletal tracts composed 20-50 spicules wide, ascending towards surface, becoming more plumose in subectosomal region, tracts separated by large subectosomal cavities of approximately same width as tracts themselves. Spongin fibres not evident. Collagen abundant in choanosomal mesohyl, associated predominantly with spicule tracts. Generally all spicule sizes dispersed throughout ectosomal and choanosomal skeletons, without clearly differentiated ectosomal and choanosomal size classes, although smaller spicules mainly found scattered between tracts whereas larger spicules mainly aligned in tracts. Spicules. Oxeas in two size classes, or more probably one class with large size range: larger oxeas slightly curved at centre, hastate relatively abruptly pointed (length 550-(622.4)-744 pm, width 13-(16.8)-21 pm); smaller oxeas straight or slightly curved, hastate abruptly pointed, occasionally styloid (length 188(241.4)-290 pm, width 4-(6.7)-11 pm). Remarks. This species has not previously been recorded having two size classes of oxeas, although Dendy (1922) notes that the main

ascending to surface; without fibre component but with heavy collagenous mesohyl. Ectosomal skeleton highly collagenous, with mineral skeleton composed of smaller oxeote spicules forming discrete, sparse, regularly distributed surface brushes eventually producing surface conules; or of larger choanosomal oxeotes protruding through surface and producing regularly spaced surface conules. Megascleres are one or two size categories of oxeas or modified (styloid, strongyloid) oxeotes. Remarks. Axinyssa and the related genus Collocalypta differ from other halichondriids in having choanosomal spicule tracts protruding slightly through a largely organic ectosome (i.e. lacking a continuous ectosomal skeletal crust), producing a finely conulose surface (Van Soest et al. 1990). Axinyssa differs from the latter genus by its plumose or vaguely plumoreticulate skeletal structure (particularly near the surface), and growth form (the latter being exclusively fistulose). The emended diagnoses and discussions given by Van Soest et al. (1990) and Hooper and Bergquist (1992) clearly differentiate the two genera, whereas the diagnosis provided by Diaz et al. (1991) did not, mainly because they did not encounter Collocalypta in the central Atlantic fauna. Worldwide there are so far 13 described species of Axinyssa, distributed throughout the tropical oceans in shallow reefs to deeper coastal waters, but only one of these have been previously described from IndoAustralian waters: A. aplysinoides (Dendy) described from the Great Barrier Reef (Burton 1934). Axinyssa aplysinoides (Dendy) (Figs 1-2) Halichondria aplysinoides Dendy, 1922: 3940, pl. 3, figs 3-5, p1.12, fig. 9. Trachyopsis aplysinoides - Burton, 1926: 78; - Burton 1934: 564. Axinyssa aplysinoides - Van Soest et al., 1990, fig. 20; - Hooper and Bergquist 1992: 101. Type material. HOLOTYPE - BMNH 1921.11.7.31: Cargados Carajos, Indian Ocean, 30 August 1905, 58m depth, coll. HMS Sealark. Material. QM G303561: Outer region of Shoal Bay, NT, 12°06.9'S, 130°49.9'E, 18 m depth, 12 October 1993, coll. CCNT stn. 136 (ref. 2176), dredge. Distribution. Cargados Carajos, Amirante, Coetivy, Egmont Reef, Seychelles Is, Indian Ocean; southeast Indonesia; Satellite Reef, Great Barrier Reef; Shoal Bay, Timor Sea, NT. 4

Beagle Gulf halichondriid sponges

I 111

Fig. 1. Axinyssa aplysinoides (Dendy). A, larger oxeas; B, smaller oxea. C, peripheral skeletal structure; B, preserved specimen QM G303561; E, live specimen (on deck).

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Fig. 2. Axinyssa aplysinoides (Dendy). Specimen QM G303561. A, Perpendicular section through skeleton showing large multispicular tracts in choanosomal skeleton, becoming more plumose in periphery; B, transverse section of ectosomal skeleton showing outer surface of sponge with tangential uni- and paucispicular tracts of both larger and smaller oxeas; C, light micrograph of section through peripheral skeleton showing plumo-reticulate subectosomal skeletal tracts and protruding larger spicules; D, hastate pointed spicule terminations on both larger oxeas (left) and smaller oxeas (right).

megascleres "vary considerably in size", with the upper size limit of 1000 x 30 pm. In the Darwin specimen, spicules are indiscriminantly scattered throughout the skeleton, without any marked localisation of spicule sizes to either ectosomal or choanosomal regions (unlike those of Topsentia or Epipolasis which have their ectosomal skeletons composed of a distinctly smaller category of spicules), and it is possible that smaller megascleres seen here (mostly scattered between the major spicule tracts) are juvenile forms of the main structural spicules. Dendy (1905) suggests that the most distinctive feature of this species is its resemblance to an Aplysina (Verongida) in external morphology, in particular to the series of minute, raised ridges forming a reticulation on the surface. These surface features, together with the ascending multispicular tracts of oxeas cemented together by granular collagen, and the spicule geometry (lacking telescoped points, occasion-

ally styloid ends), differentiate this species from other Axinyssa. We do not know whether material from the Great Barrier Reef recorded by Burton (1934) is similar to the Darwin specimen, described above, as Burton did not describe his specimen, but it is assumed that conspecificity of his specimen was checked against type material given that he had easy access to the holotype in the BMNH collection.

Genus Myrmekioderma Ehlers Myrmekioderma Ehlers, 1870: 28. Acanthoxifera Dendy, 1905: 156. Anacanthaea Row, 1911: 329. Neoprosypa de Laubenfels, 1954:189. Type species. Alcyonium granulatum Esper, 1830: 71.

Diagnosis. Massive or encrusting growth forms. Surface hispid, with characteristic excavating meandering, sinuous or straight canals 6

Beagle Gulf halichondriid sponges

and grooves (forming polygonal tuberculate plates in type species). Choanosomal skeleton collagenous, with compressed central portion composed of confused mass of larger spicules forming irregular, ascending, multispicular tracts bound together with collagen (spongin fibres present in some species but not all). Subectosomal skeleton composed of ascending tracts running radially or obliquely to surface. Ectosomal skeleton dense paratangential layer of smaller spicules forming closely adjacent brushes perpendicular to surface, with larger choanosomal spicules also protruding. Megascleres at least two distinct categories of choanosomal oxeas, strongyles, or more rarely styles, sometimes sinuous and centrally flexed, and smaller ectosomal oxeas or acanthoxeas of similar morphology. Microscleres raphides in trichodragmata, in one or more categories, larger usually sinuous or curved. Remarks. Recent revisions of this genus are provided by Bergquist (1965: 177), Van Soest et al. (1990: 31), Diaz et al. (1991) and Hooper and Levi (1993b: 1448). Myrmekioderma and Didiscus are apparently related (and both easily recognisable in the field) by their deeply sculptured sinuous and plate-like grooves on the surface, having an ectosome composed of smaller spicules forming an erect palisade over tangential larger spicules, and a similar basic choanosomal skeletal organisation (Van Soest et al. 1990; Diaz et al. 1991). Myrmekioderma lacks discorhabd microscleres, characteristic of Didiscus, but has instead bundles of sinuous raphides (trichodragmata). The genus has been traditionally defined with lightly acanthose ectosomal oxeas (e.g. Bergquist 1965; Hooper and Levi 1993b), but Diaz et al. (1991) correctly note that these ectosomal spicules are as frequently smooth as they are acanthose, and they emend the definition accordingly. Hooper and Levi (1993b) retained this genus in the family Desmoxyidae, supporting their decision with chemotaxonomic evidence based on an inferred close relationship between Higginsia and Myrmekioderma (Hooper et al. 1992). However, there is no strong morphological support for homology between the occasionally acanthose ectosomal oxeas in Myrmekioderma and the true ectosomal acanthoxeas in Higginsia. The overall similarity between the ectosomal structure, choansomal organisation and spicule composition (apart from the possession of microxeas or discorhabds, respectively) largely supports the inferred close relationship between

Myrmekioderma and Didiscus and their inclusion in Halichondriidae, as proposed by Van Soest et al. (1990). However, it must be acknowledged that structural similarities in the erect palisade of ectosomal spicules is remarkable between Myrmekioderma and Higginsia (see illustrations in Hooper and Levi 1993b), for which genetic data might provide a more informed opinion. Myrmekioderma is widespread in shallow tropical and subtropical oceans, found predominantly on hard substrates, sand and rubble substrates. One species, M granulata, has been recorded previously from northwest Australian and southern Indonesian waters (Van Soest et al. 1990; Hooper and Levi 1993b), and is thought to be one of the truly widespread coral reef sponges throughout the Indo-west Pacific (Hooper 1994). Myrmekioderma granulata (Figs 3-4)

(Esper, 1830)

Alcyonium granulatum Esper, 1830: 71, pl. 24. Myrmekioderma granulata; - Ehlers, 1870:28; - Burton 1938: 39, p1.7, fig. 42; - de Laubenfels 1954: 121, fig. 75; - Levi 1961: 14, fig. 17; - Bergquist 1965: 177, fig.27a-b; - Van Soest et al. 1990: 29, fig. 28; - Hooper et al. 1992: 265; - Hooper and Levi 1993b: 1449, figs 35-36. Acanthoxifer ceylonensis Dendy, 1905: 157, pl. 9, fig. 5; - Dendy, 1922: 129. Myrmekioderma tylota de Laubenfels, 1954: 119, fig. 74. Neoprosypa atina de Laubenfels, 1954: 190, fig. 127. Acanthoxtfer fourmanoiri Levi, 1956: 5. Material. NTM Z196: Dudley Point reef flat, East Point, Darwin Harbour, NT, 12°25.0'S, 130°49.01'E, 0-0.5 m depth, 13 September 1981, coll. J.N.A. Hooper and P.N. Alderslade, by hand. NTM Z2053: Dudley Point reef slope, Darwin Harbour, 12°25.0'S, 130°48.40'E, 6-10 m depth, 10 May 1984, coll. J.N.A. Hooper and P.N. Alderslade, SCUBA. QM G303349: East Point `bommies', 12°24.5'S, 130°48.8'E, 10 m depth, 23 September 1993, coll. J.N.A. Hooper, L.J. Hobbs and B. Alvarez, SCUBA. NTM Z430: Lee Point, Darwin, 12°19.02'S, 130°53.01'E, 0-0.2 m depth, 13 December 1981, coll. J.N.A. Hooper, by hand. Comparative material (Refer to Hooper and Levi 1993b: 1449 for additional material examined). QMG300819: W of Port Musgrave, 7

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Gulf of Carpentaria, Qld 12°04.6'S, 139°21.5'E, 54 m depth, 25 November 1991, coll. S. Cook, RV Southern Surveyor, dredge. QMG303505: W of Duyfken Point, 12°28.4'S, 141°00.8'E, 53 m depth, 6 November 1993, coll. S.D. Cook and J.A. Kennedy, RV Southern Surveyor, trawl. QMG303172: NE side Flinders Reef, N. of Moreton I., SE Qld, 26°58.6'S, 153°29.2'E, 9 m depth, 31 May 1993, coll. J.N.A. Hooper, SCUBA. QMG303135: Lagoon, Truk Atoll, Caroline Is, 7°24.9'N, 151°44.4'E, 31 m depth, 24 March 1992, coll. NCI (CRRF). Distribution. Dudley Point, East Point, Lee Point, Darwin Harbour, NT; Port Essington, Cobourg Peninsula; Cumberland Strait, Wessel Is, NT; Parry Shoals, Arafura Sea, NT; Enderbry I., Direction I., Dampier Archipelago, WA; Hibernia Reef, Sahul Shelf, Territory of Ashmore and Cartier; Moreton Bay region, Qld; western Gulf of Carpentaria, Qld; Madagascar, Aldabra, Seychelles, Gulf of Manaar, SE Indonesia, Ponape, Truk (Chuuk), Ebon Atolls, Palau, Ifaluk, Chesterfield Is (refer to references in Hooper and Levi 1993b). Habitat. Shallow-water rock and coral platforms, coral pools, coral rubble, usually heavily sedimented, or in spur-and-grooves of fringing reefs; in deeper water found on exposed reef heads in gravel and mud substrates; intertidal to subtidal depths of 60 m. Description. Massive, subspherical or elongate bulbous, up to 1 m long, 1 m wide, 0.5 m thick; partially burrowing in soft sediment or excavating coralline substrate. Oscules large, discrete, conspicuous, usually situated in excavated grooves on apical surface, and each oscule with raised lip. Colour. Bright orange to dark orange-brown exterior (Munsell 7.5YR 7/10-5YR 6/10), often silt-covered in life; paler orange-yellow interior; orange-brown in ethanol. Texture. Firm but compressible, harsh with hispid surface; interior soft, producing mucus. Surface. Opaque and membranous, covered by rounded, raised polygonal plates separated by grooves and canals, producing pineapplelike external surface. Ectosomal skeleton. Detachable; distinct crust of smaller ectosomal spicules forming continuous paratangential palisade, associated with and protruding through heavy collagenous ectosomal layer, and dispersed amongst larger choanosomal oxeas and styles, the latter moreor-less erect and ascending to surface. Subecto-

somal region dense, collagenous, cavernous in places, with tracts of larger choanosomal oxeas supporting ectosomal crust. Choanosomal skeleton. Skeletal structure vaguely halichondroid reticulate, with compressed central portion, oblique subectosomal skeletal tracts supporting paratangential ectosomal layer. Choanosomal spicule tracts composed of up to 50 choanosomal spicules abreast, ascending to surface, becoming both sparser and more confused in peripheral skeleton. Thick fibres visible only in some specimens (being fully cored by spicules in others), with differentiated primary, multispicular, ascending fibres and transverse paucispicular fibres. Fibre meshes up to 300 pm diameter. Collagen abundant, very granular and pigmented in choanosome. Choanocyte chambers small, oval, 40-70 pm diameter. Spicules. Two size classes of megascleres recognised: choanosomal and ectosomal; variable megasclere geometry, ranging from fusiform oxeas, strongyloxeas, strongyles or styles; spicule terminations range from pointed to telescoped, styloid or sometimes with terminal deformities; and spicules may be completely smooth or lightly and evenly acanthose (Berguist 1965). In Beagle Gulf populations choanosomal megascleres predominantly oxeas, less often strongyloxeas or styloid, usually larger than ectosomal spicules, often with microspination (length 495-(615.7)-950 pm, width 8-(18.2)-22 pm). Smaller ectosomal megascleres invariably oxeote, predominantly smooth but occasionally evenly microspined (length 305-(502.4)-580 pm, width 3-(7.5)-10 pm). Microscleres raphides in bundles (trichodragmata) (110-155 x 10-15 pm). Remarks. Live specimens of M. granulata are distinctive in their characteristic dark orange colouration, mango-like texture, massive growth form and plate-like surface ornamentation. The species is now relatively well documented and known to be widely distributed within the Indo-west Pacific region, extending from Madagascar to NW Australia, Indonesia and the central west-Pacific islands and atolls (Esper 1830; Ehlers 1870; Dendy 1905, 1922; Burton 1938; Levi 1956, 1961; de Laubenfels 1954; Bergquist 1965; Van Soest et al. 1990). In the southwest Pacific the species is rare, so far known only from isolated records (Flinders Reef off Moreton Bay (27°S) and Chesterfield Islands (21.5°S latitude; Hooper and Levi 1993b and unpublished data). Surprisingly, the spe8

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J.N.A. Hooper et al.

Fig. 4. Myrmekioderma granulata (Esper). Specimen NTM Z3249. A, perpendicular section through skeleton, showing compressed central portion of skeleton, oblique subectosomal spicule tracts and cavities, and paratangential ectosomal skeleton; B, transverse section of ectosomal skeleton showing outer surface of sponge with palisade of smaller ectosomal oxeas dispersed amongst larger choanosomal oxeas and styles; C, terminations of choanosomal strongyloxeas; D, termination of ectosomal oxen and raphide microsclere. cies has not yet been discovered from the Great Barrier Reef, despite some intensive recent collections from many reefs, and it is possible that M. granulata is merely an incursive into the south Pacific region. Populations of M. granulata in the central west-Pacific region have been frequently recorded (refer to records in de Laubenfels (1954) and Bergquist (1965)), whereas Australian and southern Pacific populations were only recently published (Hooper and Levi 1993b; Hooper 1994). Nevertheless, its distribution within Australia is now relatively well understood, extending as far south as 27°S latitude on the eastern coast (restricted to inshore waters), and to 21.5°S latitude on the western coast of the continent, living in both coastal and offshore waters. Within the Beagle Gulf Marine Park this species has been seen on many shallow inshore fringing coral reefs and coral platforms, especially in the Darwin and Cobourg Peninsula regions (Hooper

and Levi 1993b), and it is also abundant on the more pristine oceanic coral reefs off the coast of northwest Australia (Hooper 1994) where it grows to a much larger size and ranges to greater depths than do the inshore populations. Bergquist (1965) provided a detailed analysis of morphometric variability in M. granulata, which she correlated to some extent with regional populations of the species. Characters found to vary between populations included surface sculpturing, live colouration, geometry, spination and size of megascleres. These features are also shown to vary between the inshore northwest Australian populations and those from other localities. Specimens from the oceanic coral reefs of the Sahul Shelf and those from New Caledonia have meandering ridges excavating the apical surface (rather than discrete polygonal plates) (compare Hooper and Levi 1993b: fig. 36A and the present work, Figure 3F-G); spicules are virtually entirely oxeote and

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Beagle Gulf halichondriid sponges

well as raphide microscleres overlaying larger choanosomal oxeas, typically showing a strict localisation of spicule sizes, whereas in Topsentia there there may or may not be size difference between the ectosomal and choanosomal spicules, and if present it is usually not consistent (i.e. spicule size may not be exclusive to any particular region) (Diaz et al. 1991, 1993). Van Soest et al. (1990) include Trachyopsis in synonymy with Topsentia, but this only applies to the type species (others subsequently distributed amongst Axinyssa and Spongosorites). The genus is found in all tropical and subtropical oceans, extending from shallow waters to moderate depths. Within the Indo-Australian region eight species of Topsentia has been previously recorded: T. solicla (Ridley and Dendy) with several junior synonyms (Hooper and Wiedenmayer 1994) from Tahiti, New Hebrides (Vanuatu), Christmas Island (Indian Ocean), Great Barrier Reef, and Ternate, Indonesia (Ridley and Dendy 1887; Keller 1891; Kirkpatrick 1900; Burton 1934), T. glabrata (Keller) from Ternate, Indonesia (Keller 1891), T. indica Hentschel from Am Island, Indonesia (Hentschel 1912), T. dura (Lindgren) from Gaspar Straits, Java Sea, Indonesia (Lindgren 1897, 1898), T. variabilis (Lindgren) and T. armata (Lindgren) from Java, South China, southern Philippines and Arafura Seas (Lindgren 1897, 1898; Hentschel 1912; Wilson 1925); T. cavernosa (Topsent) from the Moluccas, Indonesia (Topsent 1897; Desqueyroux-Faundez 1981), and T. halichondrioides (Dendy) from the Gulf of Manaar, southern Philippines, northern Great Barrier Reef, New Zealand (Dendy 1905; Wilson 1925; Burton 1934; Bergquist 1970).

smooth (whereas some inshore specimens have acanthose ectosomal oxeas and styloid modifications to choanosomal oxeas); and skeletal structure may be more cavernous (whereas most inshore samples appear to be more compact) (Hooper and Levi 1993b and present study). It is possible that these differences are indicative of a sibling species relationship (rather than conspecificity), but this is not detectable solely on the basis of morphological data. Genus Topsentia Berg [Anisoxya] Topsent, 1898: 225 (junior homonym of Anisoxya Mulsant, (Coleoptera)). Topsentia Berg, 1899: 77. Trachyopsis Dendy, 1905: 147. Oxeostilon Ferrer-Hernandez, 1922: 10. Alloscleria Topsent, 1927: 6. Coelocalypta Topsent, 1928: 167. Laminospongia Pulitzer-Finali, 1983: 546. Type species. Anisoxya glabra Topsent, 1898, by monotypy. Diagnosis. Massive, amorphous or lobate growth forms, with brittle texture. Choanosomal skeleton completely lacking spongin, with mineral skeleton composed of oxeas in confused, directionless arrangement closely packed around aquiferous system, lacking any multispicular tracts. Subectosomal skeleton sometimes with subdermal cavities, but never large. Ectosomal skeleton with compact paratangential or erect layer of oxeas producing microhispid surface, typically without definite organisation but often closely compacted producing radial palisade. Megascleres oxeas in two or more size classes, including twisted, sinuous and contort modifications, usually without consistent size differences between ectosomal or choanosomal spicules. Remarks. The genera Topsentia, Epipolasis and Petromica have completely confused halichondroid choanosomal skeletal structure, with spicules criss-crossing in deeper parts of the skeleton, they lack spongin within the choanosomal skeleton, and the only recognisable organisation is found at the surface in the form of spicule brushes. Species of Topsentia are most distinctive in the disorganisation of the choanosomal skeleton and lack of spongin (hence the brittle consistency), and they are typically drab in colour (Van Soest et al. 1990; Diaz et al. 1991). Epipolasis has a tangential felt-like ectosomal crust of smaller oxeas as

Topsentia halichondrioides (Dendy) (Figs 5-6) Trachyopsis halichondrioides Dendy, 1905: 147, p1.10, fig.I0. - Burton 1926: 75, figs 6-7; Burton 1934: 564; - Bergquist 1961: 185, fig.9; - Bergquist 1970: 34. Type material. HOLOTYPE - BMNH 1907.2.1.44: Galle, Periya Paar, Gulf of Manaar, Ceylon (Sri Lanka). Other Material. NTM Z3262: SW side of cliff face, Table Head, Port Essington, Cobourg Peninsula, NT, 11°13.5'S, 132°10.5'E, 5 m depth, 11 September 1986, coll. J.N.A. Hooper and C. Johnson, SCUBA. QM G303442: W

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J.N.A. Hooper et al.

Fig. 6. Topsentia halichondrioides (Dendy). Specimen QM G303442. A, perpendicular section through skeleton showing disorganised ascending halichondroid choanosomal skeleton supporting the plumose subectosomal skeleton of larger oxeas, with a thin tangential ectosomal layer of smaller oxeas just below surface; B, transverse section of ectosomal skeleton showing outer surface of sponge with erect palisade of larger oxeas, with smaller oxeas lying below and tangential to this layer; C, light micrograph of section through peripheral skeleton showing distinct demarkation between the halichondroid reticulate choanosomal skeleton and the nearly plumose subectosomal skeleton; D, larger oxea (left) with faintly telescoped point, and sharply smaller oxea (right). in dimensions; T. dura is greenish alive, olivebrown when preserved, stony consistency, small sunken oscules, two sizes of oxeas up to 600 x 20 pm and 260 x 6 pm, respectively, and an erect, continuous ectosomal palisade; T. armata is tuberculate, fibrous consistency, minute oscules, very large oxeas up to 1700 x 48 pm, and a sparse ectosomal skeleton; T. variahilis is massive flattened, grey-brown preserved, fibrous consistency, with prominent surface microconules, minute oscules, two sizes of oxeas, up to 770-1160 x 16-30 pm and 520-650 x 10-24 pm respectively, with an oblique, plumose ectosomal skeleton composed of discrete (not continuous) brushes, and multispicular tracts in the choanosomal skeleton; T indica is gray preserved, fibrous consistency, small oscules with slightly raised margins, oxeas in two sizes, up to 800 x 23-55 pm and 380 x 18 pm, respectively, ectosomal skeleton radial, well devel-

oped; T. cavernosa is massive, has a hard texture, moderately well developed erect ectosomal skeleton composed of only marginally smaller oxeas than in the choanosomal skeleton, and oxeas are 600-1000 x 17-20 pm.

Topsentia dura (Lindgren) (Figs 7-8)

Halichondria dura Lindgren, 1897: 480. Lindgren 1898: 286-287, pl. 17, fig. 2, pl. 19, fig. 3. Type material. Fragment of holotype BMNH 1929.11.26.41: Selat Kelasa (Gaspar Straits), Java Sea, Indonesia, coll. C. Aurivillius, 1891. Other Material. NTM Z3195: East Point `bommies', Darwin, NT, 12°24.5'S, 130°48.8'E, 9 m depth, 16 September 1987, coll. N. Smit, 14

Beagle Gulf halichondriid sponges

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Fig. 7. Topsentia dura (Lindgren). A, larger (predominantly) choanosomal oxea; B, smaller (predominantly) ectosomal oxea; C, peripheral skeletal structure; D, preserved specimen NTM Z3I95; E, specimen NTM ZI442.

Colour. Yellow-green to dark green in life (Munsell 5Y 8/4 - 2.5GY 5/4), white in ethanol. Texture. Very firm, incompressible, brittle, easily broken. Surface. Optically smooth but uneven, lumpy; encrusted in places with detritus; hispid. Ectosomal skeleton. Continuous erect palisade of protruding single spicules or paucispicular brushes, composed mainly of larger oxeas, standing erect on ascending peripheral choanosomal tracts and protruding through surface only slightly beyond collagenous membrane; sparse tangential layer of smaller oxeas at base of protruding larger spicules, presumably lying on ectosomal membrane. Choanosomal skeleton. Dense halichondroid disorganised mass of single spicules, mostly larger oxeas, organised only around lacunae

SCUBA. NTM Z3178: Dudley Point Reef, East Point, Darwin, NT, 12°25.0'S, 130°49.1'E, 0.5 m depth, 10 September 1987, coll. N. Smit, by hand. NTM Z1442: Blue Hole, Gunn Point, NT, 12°09.0'S, 131°00.5'E, 25 m depth, 19 August 1983, coll. J.N.A. Hooper and P.N. Alderslade, SCUBA. Distribution. Java Sea, Indonesia; East Point Aquatic Reserve and Gunn Point, Darwin Harbour, NT. Habitat. Laterite rock and fringing coral reef, sandy substrate; intertidal-subtidal depths. Description. Massive to lobate, irregularly anastamosing lobes, up to 110 mm long, 40 mm diameter. Oscules small, less than 2 mm diameter, discrete, scattered over surface of lobes, sunken in slight depressions on surface, without visible oscular rim. 15

J.N.A. Hooperet al.

Fig. 8. Topsentia dura (Lindgren). Specimen NTM Z3195. A, perpendicular section through skeleton of branch showing halichondroid reticulate choanosome and plumose subectosomal skeletons; B, transverse section of ectosomal skeleton showing outer surface of sponge with a plumose ectosomal skeleton composed of protruding larger oxeas and a sparse tangential skeleton of smaller oxeas at their base; C, light micrograph of section through peripheral skeleton showing faint demarkation between the halichondroid reticulate choanosomal skeleton and the nearly plumose subectosomal skeleton; D, sharply pointed fusiform larger oxea (left) and smaller oxea (right).

and in peripheral skeleton, becoming plumose in periphery. Choanosomal and subectosomal regions equally cavernous, with occasionally large lacunae (>500 pm diameter) but mostly smaller oval meshes (