Holotype: MSNG 60134, PH-1, 13/01/2005, Timur (Bunaken Island), about 20 m depth. Paratype: MSNG 60135, PH-27, 13/01/2005, same locality as holotype, about 20 m depth.

BU-82, 22/03/2000, Lekuan II (Bunaken Island), 20 m depth. BU-580, 27/06/2004, Alung Banua (Bunaken Island), 16 m depth. INDO-079, 08/05/2005, Tanjung Kopi (Manado Tua), unknown depth, N01°39'07.4"; E124°41'58.8". INDO-278, 11/05/2005, Tansung Pisok (Manado), unknown depth, N01°34'31.2"; N01°34'31.2". INDO-336, 12/05/2005, Bualo (Manado), unknown depth, N01°37'00.7"; E124°41'21.9". INDO-339, 12/05/2005, Bualo (Manado), unknown depth, N01°37'00.7"; E124°41'21.9".

Cushion-shaped, sub-spherical sponge; yellow, brown or dark orange. Strongyloxeas, styles and subtylostyles not separable in size categories, forming ascending tracts protruding through the sponge surface.

The sponge is massive, sub-spherical or lobate (Fig. 2A, B). The holotype (Fig. 2A) is a fragment about 1.5 cm long and 1 cm thick, sampled from a large globular specimen; the paratype is a small portion, approximately 2.5 cm long and 1 cm thick, of a large cushion-shaped specimen approximately 60 cm across. The paratype (Fig. 2B) shows a sort of lobate organisation, with roundish parts connected by bottleneck narrowings. The colour in life is yellow, varying between orange and brown according to light exposure; it is not uniform, but presents dark red spots or stripes (Fig. 2A, B). The sponge is always yellow inside. Alcohol-preserved specimens are dark green-brown. The sponge surface is smooth, but microscopically hispid. Ostia, grouped in distinct areas on the sponge surface, have such a large diameter that they are visible to the naked eye. Oscula are flush, more or less circular, with a very low rim. Converging exhalant canals are visible in their lumen (Fig. 2A). Consistency is hard when preserved.

Figure 2. 

Aaptos lobata sp. n. A, B specimens in situ: A holotype B paratype C skeleton organisation (transverse section) D peripherical part of the skeleton E large strongyloxea F thin style.

Skeleton. The choanosomal skeleton is radiate, regular in the outer part of the sponge and more irregular in the deeper part. Due to high spicule density, spicule tracts are not easily detectable (Fig. 2C, D). In the ectosome, the smallest styles are arranged in palisade and do not form brushes, whereas the spicules of intermediate size are concentrated in the sub-ectosomal layer and protrude through the surface with their tips (Fig. 2C, D). Abundant spheroulous cells, approximately 12 µm in diameter, are detectable in the choanosome.

Spicules. Three size categories of megascleres, partially overlapping at the extremities of their size-frequency distributions. The larger spicules are straight strongyloxeas with acerate or slightly stepped tips (Fig. 2E) and often evident axial canal. Intermediate and small megascleres, straight or slightly curved, vary in shape from strongyloxeas to subtylostyles to thin styles (Fig. 2F). The measurements are given in Table 2.

The name refers to the multi-lobate organisation of the sponge.

The genus Aaptos Gray, 1867, according to van Soest et al. (2016), encompasses in total 24 valid species, 10 of which distributed in the tropical Indo-Pacific and adjacent areas (Table 2). The descriptions are usually based on the very few diagnostic features detectable in the genus, making it difficult to differentiate species (Kelly-Borges and Bergquist 1994). The radial skeleton, the arrangement of the megascleres and the spicule morphology, being quite uniform within the genus, are seldom accurately described (Kelly-Borges and Bergquist 1994). Therefore, the importance of other morphological characters useful to differentiate species, such as colour, collagen distribution in the cortex, shape and arrangement of megasclere tracts, presence of interstitial spicules, is greatly emphasised (Kelly-Borges and Bergquist 1994). Recently, Carvalho et al. (2013) stressed the importance of other morphological aspects as main characters for the species distinction in the genus, such as external morphology, colour, shape and size of the megascleres, ectosomal spicules arrangement (palisade or bouquets).

The skeletal organisation of Aaptos lobata sp. n. is comparable with that of the type species of the genus, the Atlantic-Mediterranean Aaptos aaptos (Schmidt, 1864) (see van Soest 2002). Aaptos lobata sp. n. has been compared with all the congeneric species and especially with those recorded from the Indo-Pacific and adjacent areas, whose characteristics are reported in Table 2. Aaptos ciliata (Wilson, 1925) has spicules different in size and shape; in particular, the ectosomal styles are longer (1,100–1,300 × 4 µm). The species A. conferta Kelly-Borges & Bergquist, 1994, is an encrusting sponge, black outside and yellow inside, that has oxeas as additional spicules, whereas A. globosa Kelly-Borges & Bergquist, 1994 differs in colour (dark red outside and yellow inside) and in the skeletal organisation, since choanosomal tracts are thick and ramified under the surface and the intermediate megascleres form tracts. Aaptos horrida (Carter, 1886) and A. nuda (Kirkpatrck, 1903) have oxeas as megascleres instead of strongyloxeas; A. laxosuberites (Sollas, 1902) is encrusting, white in alcohol and has strongyloxeas and long tylostyles as megascleres. Aaptos niger Hoshino, 1981 is a black, massive sponge, usually embedding exogenous material; while A. rosacea Kelly-Borges & Bergquist, 1994, is red outside and yellow inside and differs from the new species in skeletal arrangement and size of spicules. The species A. suberitoides (Brøndsted, 1934), black outside and dark red inside, has a very simple skeleton of styles only, while A. tenta Kelly-Borges & Bergquist, 1994, brown in colour, has a peculiar skeletal arrangement and different spicules. Since no species in this vast geographic area matches with the characters of our specimens, we decided to erect a new species.

BU-98, 23/03/2000, Lekuan II (Bunaken Island), 5 m depth. BU-289, 17/05/2001, Raymond’s Point (Bunaken Island), unknown depth. BU-533, 21/06/2004, Bualo (Manado Tua Island), about 8 m depth. BU-545, 23/06/2004, Raymond’s Point (Bunaken Island), about 20 m depth. BU-562, 26/06/2004, Bualo (Manado Tua Island), unknown depth.

Encrusting sponge 3–6 mm thick; the largest examined specimen (BU-289) is approximately 10 cm in diameter. The consistence is firm; the body of the sponge lacunose. The surface is irregular, with extended verrucous areas covered by sand and largely colonised by epibiotic ascidians, algae and hydroids (Fig. 3A). In the microscopic observation, the surface appears micro-hispid. The colour of living specimens is orange; when preserved, the sponge becomes yellowish-green.

Skeleton. Tethytimea tylota does not have a distinguishable ectosomal skeleton or a proper cortex; the choanosomal skeleton is formed by bundles of big tylostyles of 100–200 µm directed outwards (Fig. 3B). Close to the surface, these main bundles support fans of small tylostyles hispidating the sponge surface (Fig. 3B, C).

Spicules. Megascleres are straight tylostyles with a slightly developed head (Fig. 3D). They can be distinguished into two size classes (Fig. 3E, F); tylostyles I measure 930 - (1,104.8 ± 146.7) - 1,339 × 12.5 - (17.8 ± 3.4) - 25 µm; tylostyles II (Fig. 3D) measure 490 - (576.6 ± 72.5) - 660 × 5 - (6.6 ± 2.0) - 10 µm and form the superficial fans that protrude out of the surface; microscleres are two kinds of asters (Fig. 3G–K). Oxyspherasters (Fig. 3G–I) with thick ramified or rounded, often bifurcated rays, measuring 65 - (122.5 ± 39.6) - 200 µm. Tylasters with rays variable in length ending with apical groups of spines variable in number (Fig. 3J, K); they measure 7.5 - (11.1 ± 1.9) - 16.3 µm. Microscleres are abundant throughout the sponge, but more concentrated close to the surface (Fig. 3L), where the smallest tylasters form a thin, continuous layer (Fig. 4H, inlet).

Figure 3. 

Tethytimea tylota (Hentschel, 1912) A specimen in situ (BU-562) B cross section showing bundles of big tylostyles (full arrow) and the microscleres (empty arrow) CSEM image showing fans of small tylostyles (full arrow) and microscleres (empty arrow) of T. tylota (t), below the sponge Stelletta sp. n. (s) involved in the association D small tylostyle E, F heads of tylostyles G–I oxyspherasters J, K tylasters L groups of microscleres.

This sponge was exclusively found as epizoic on Stelletta tethytimeata sp. n. (see below). It has been attributed to T. tylota for its skeletal organisation, made of bundles of main tylostyles supporting superficial fans of small tylostyles, the superficial layer of tylasters (present also in the holotype), the size and shape of megascleres and microscleres (Sarà 2002). The genus Tethytimea is monospecific and T. tylota was found at Aru Island (Indonesia). This is the first record of this species since the original description (Hentschel 1912). In the revision of the genus (based on the re-examination of the type material), Sarà (2002) confirmed the presence in the holotype of very rare spheres; these spicules were not detected in the present specimens as in the paratype (Sarà 2002).

It is interesting to note that the holotype of T. tylota was encrusting on a stone and in association with another sponge (Sarà 2002).

See below.

Holotype: MSNG 60136, BU-289, 17/05/2001, Raymond’s Point (Bunaken Island), unknown depth. Paratype: MSNG 60137, BU-562, 26/06/2004, Bualo (Manado Tua Island), unknown depth.

BU-533, 21/06/2004, Bualo (Manado Tua Island), about 8 m depth. BU-545, 23/06/2004, Raymond’s Point (Bunaken Island), about 20 m depth. BU-98, 23/03/2000, Lekuan II (Bunaken Island), 5 m depth.

Massively rounded yellow sponge; the colour changes after fixation. Megascleres are anatriaenes with characteristic bending and a single type of oxeas; microscleres are represented by a heterogeneous set of tylasters and oxyasters.

The sponge is light yellow-lemon in vivo (Fig. 4A); the colour changes in the preserved specimens, becoming dark-brown to blackish. It is almost totally covered by the associated epibiotic species T. tylota (see above), with the exception of the oscula that, protruding from the surface of T. tylota, are clearly distinguishable for their different colour (Figs 3A, 4A). Since the external sponge T. tylota is thinly encrusting, most of the mass of the associated sponges is due to S. tethytimeata sp. n. that can be as large as 10 cm across (Fig. 4A, B).

Skeleton. The cortex is a collagenous layer 400-700 µm thick (Fig. 4B); the triaenes have their clades tangential to the surface and sometimes protrude from it (Fig. 4C), merging in the tissue of the epibiotic T. tylota. The choanosomal skeleton is formed by tracts of oxeas without a clear radial arrangement with microscleres scattered in between (Fig. 4D). Towards the sponge surface, the spicule density lowers and oxeas are more or less parallelly arranged (Figs 3C, 4B, D).

Spicules. Megascleres are anatriaenes (Fig. 4E), with straight, sharp-pointed rhabdome of 570 - (708.2 ± 119.3) - 800 × 10 - (15.7 ± 3.8) - 22.5 µm and clads of 80 - (113.4 ± 43.3) - 225 × 7.5 - (9.0 ± 2.6) - 12.5 µm with sharp tips and characteristic bending. Oxeas straight, fusiform, with sharp tips (Fig. 4F), sometimes modified into styles; they measure 1274 - (1514.5 ± 145.3) - 1950 × 20 - (24.5 ± 3.9) - 30 µm. Microscleres encompass a heterogeneous set of tylasters and oxyasters (Fig. 4G), with 4–9 rays, with spines along the rays or grouped at the extremities 20 - (27.2 ± 4.4) - 35 µm.

Figure 4. 

Stelletta tethytimeata sp. n. A specimen in situ (BU-533), partially cut to put in evidence the association with Tethytimea tylota. The black arrow indicates the thin layer of the external sponge (T. tylota, orange) while the white arrow indicates S. tethytimeata sp. n. B paraffin-embedded section of T. tylota (t) and S. tethytimeata sp. n. (s) co and ch indicate, respectively, the cortex and the choanosome of S. tethytimeata sp. n. C cross section showing triaenes close to the boundary between T. tylota (t) and S. tethytimeata sp. n. (s) D bundles of oxeas reaching the boundary between T. tylota (t) and S. tethytimeata sp. n. (s) E anatriaene F oxea G micrasters H histological preparation showing the cortex (co) of S. tethytimeata sp. n. The arrow points to the collagenous layer between S. tethytimeata sp. n. and T. tylota (t). The inset shows the layer of tylasters of T. tylota (arrow).

The name refers to the association with Tethytimea tylota.

Stelletta tethytimeata sp. n. is characterised by one type of triaenes and by a single category of oxeas. Out of the 146 species of Stelletta, distributed in all the oceans (van Soest et al. 2016), 49 are from the tropical Indo-Pacific area (van Soest 1994). However, they all differ from the new species in colour, skeletal organisation and especially in the spicule features. They show different categories of megascleres (oxeas of different sizes, plagio-, orto- and dico-triaenes) and microscleres. In particular, 10 species of the tropical Indo-Pacific Stelletta species present a single type of triaenes: S. bocki Rao, 1941, S. brevioxea (Pulitzer-Finali, 1993) and S. cavernosa (Dendy, 1916) have ortotriaenes; S. brevis Hentschel, 1909, S. centroradiata Lévi and Lévi, 1983, S. centrotyla Lendelfeld, 1907 and S. herdmani Dendy, 1905 have plagiotriaenes; S. herdmani var. robusta Thomas, 1979 has protriaenes, whereas S. hyperoxea Lévi and Lévi, 1983, S. vaceleti (Lévi and Lévi, 1983), S. phialimorpha Lévi, 1993 and S. digitata (Pulitzer-Finali, 1993) have dicotriaenes. Actually, Stelletta tethytimeata sp. n. is the only species of the genus in this area possessing anatriaenes (peculiar for the characteristic clad bending) and a single category of oxeas. It is therefore justified, based on the five specimens in association with Tethytimea tylota encountered in this region, to erect a new species.

The associated specimens of T. tylota and S. tethytimeata are flat or cushion-shaped with big, rounded lobes and wide oscular structures (Figs 3A, 4A).

By superficial analysis, the two associated species could appear as a single large individual sponge. The external species (T. tylota) can be detached with difficulty from the internal one (S. tethytimeata sp. n.); the contact area may be observed in SEM images (Fig. 3C) and by histological preparations where the presence of a thin collagen layer of separation between the two species is detectable (Fig. 4B, H). Histological preparations clearly show the presence of the cortex of S. tethytimeata sp. n. made by a collagen layer up to 700 µm thick (Fig. 4B, H). In the cortex, collencytes are clearly visible and pigmentary cells are numerous (Fig. 4H).

The two associated species are quite common in North Sulawesi, always in association, generally in dim-light conditions, at a maximum depth of 20 m.

BU-560, 26/06/2004, Bualo (Bunaken Island), unknown depth. BU-575, 27/06/2004, Alung Bauna (Bunaken Island), 27 m depth.

The sponge has a massive and irregular shape, a large size, up to 50 cm in diameter, and was exclusively found partially covered by Amphimedon cf. sulcata (see below). In the part not covered by the epibiotic sponge, R. distincta is yellow-lemon (Fig. 5A), or dark green (Fig. 5B), turning black when cut or preserved. Wide oscular areas are often evident (Fig. 5A, B).

Skeleton. Spherasters are located in the outer part of the sponge, but do not form a real cortex (Fig. 5C, D). The choanosomal skeleton consists of scattered oxeas which tend to form radial tracts towards the peripheral part (Fig. 5C). Oxyasters and oxyspheraster are dispersed in the choanosome.

Spicules. Megascleres are fusiform oxeas (Fig. 5E) with rather sharp tips, 720 - (832.5 ± 65.7) - 990 × 10 - (13.3 ± 2.9) - 20 µm. Microscleres are spherasters of variable size, 12.5 - (29.5 ± 6.4) - 35 µm in diameter (Fig. 5F), with a large centre and thick rays with sharp or bifurcated tips; oxyasters (Fig. 5G) with small centre and thin rays, 35 - (49 ± 8.1) - 65 µm in diameter; oxyspherasters with well-developed centre (Fig. 5H), 10 - (15.1 ± 2.6) - 20 µm.

Figure 5. 

Rhabdastrella distincta (Thiele, 1903) A, B specimens in situ (r), partially covered by the epibiotic sponge Amphimedon cf. sulcata Fromont, 1993 (a) specimen of Figure 5A is BU-575, that of Figure 5B is BU-560 CSEM image of a cross section of R. distincta (r) showing the radial tracts of oxeas in proximity of the external part, a indicates the epibiotic sponge A. cf. sulcataD histological preparation of R. distincta (r) and A. cf. sulcata (a) showing spherasters (black arrow) in the peripheral part, and oxeas of R. distincta (white arrow) penetrating the tissues of A. cf. sulcataE oxea F spheraster G oxyaster H oxyspheraster.

The Indonesian specimens fit with the description of R. distincta in having the same skeletal organisation (characterised by oxeas scattered in the inner part of the sponge and radially arranged close to the surface), absence of triaenes, spherasters in the peripheral part, oxyasters and oxyspheraster scattered in the choanosome. Spicule sizes are comparable to those of the type species that are fusiform oxeas of 850 × 25 µm, spherasters up to 40 µm, oxyasters up to 80 µm and oxyspherasters of 15 µm (see Uriz 2002). The principal difference with Thiele’s original description is that smooth microscleres were not observed and a real cortex is not detectable in the studied specimens.

This is the first record of the species since the original description of Thiele (1900) based on two specimens from Ternate, Indonesia.

See below.

BU-560, 26/06/2004, Bualo (Bunaken Island), unknown depth. BU-575, 27/06/2004, Alung Bauna (Bunaken Island), 27 m depth.

The sponge is flat, with a roundish contour, about 1 cm thick, without visible oscules. It is completely free of epibiotic organisms. Colour in situ may be greyish-white (Figs 5A, 6A) or pale cerulean (Figs 5B, 6B), off-white to greyish in the preserved state. The sponge shows ridges and grooves, covered by a very thin membrane, that give a typical convoluted or brain-like aspect to its surface (Fig. 6B).

Skeleton. The ectosomal skeleton is a reticulation of pauci-spicular tracts (3-4 spicules) (Fig. 6C) organised in quite regular triangular meshes with scarce spongin at the nodes. The choanosomal skeleton (Fig. 6D) is formed by a reticulation of multi-spicular tracts and round meshes of approximately 60 µm in diameter, with abundant scattered spicules. The spicule tract extremities barely protrude from the sponge surface, causing micro-hispidation.

Spicules. Megascleres are straight or slightly curved oxeas with sharp tips; they measure 125 - (188.9 ± 33.5) - 247.5 × 2 - (5.2 ± 3.4) - 12.5 µm (Fig. 6E); numerous thin oxeas are present (Fig. 6F); microscleres are very thin, C-shaped, sigmas 10 - (12.9 ± 1.5) - 15 × ≤ 1µm (Fig. 6G).

Figure 6. 

Amphimedon cf. sulcata Fromont, 1993 A, B specimens in situ (a), partially covering the associated sponge Rhabdstrella distincta (r), specimen BU-560a1 in Figure 6A, BU-560 in Figure 6BCSEM image of the ectosome DSEM image of the choanosome E oxea F thin oxea G sigma.

The sponge here described has a skeleton organisation fitting with the diagnosis of the genus Amphimedon that is characterised by an ectosomal skeleton of tangential fibres forming meshes, covered by a thin membrane and by a choanosomal skeleton formed by a plumose, irregular reticulation of multispicular tracts (Desqueyroux-Fáundez and Valentine 2002).

Our specimens are similar to A. sulcata, especially for the very characteristic surface: “meandering parallel ridges, interspersed with spaces, give a convolute or brain-like appearance to the surface” (Fromont 1993), for the thin membrane covering the ridges and the absence of abundant spongin.

Among the Indo-Pacific species of Amphimedon, only A. sulcata has sigmas similar in size (13 - (15.9) - 16.9 µm) to our specimens, but its oxeas (122 - (139) - 153 × 3 - (4.5) - 5.3 µm) are smaller than those we observed. Another difference is in the colour: “mauve alive, cream or fawn in alcohol” in A. sulcata (Fromont, 1993).

Amphimedon cf. sulcata is not tightly attached to Rhabdastrella distincta, and the two sponges can be separated rather easily. Frequently, wide areas of R. distincta are not covered by the outer sponge (Figs 5A, B, 6A, B), and exhalant and probably also inhalant parts of R. distincta are in these portions, free from the epibiont.

In the boundary between the two sponges, a thin collagenous layer is present. Both in the histological preparations and in SEM images, the oxeas of R. distincta are clearly visible, protruding out of the surface and penetrating inside the tissues of the external sponge (Fig. 5C, D), as it is usual in similar associations (Ávila et al. 2007). This association was frequently observed in North Sulawesi, usually below a depth of 30 m.

Holotype: MSNG 60138, PH-58, 17/01/2005, Tiwoho (Bunaken Island), about 20 m depth.

Dark green, highly branched sponge with an irregular ectosomal skeleton of rectangular, paucispicular meshes and multispicular choanosomal fibres, forming an irregular reticulation. Oxeas are mucronate.

Highly branched sponge (Fig. 7A) with repent habit. Anastomosing branches are flattened, 4–8 mm in diameter, creeping over the substrate. Colour in situ is dark green to dark brown, greenish in alcohol or in the dried state. Consistence soft and brittle; the sponge easily crumbles when dried. Surface slightly rough, irregular; when the transparent membrane is preserved, it gives a smooth appearance at the macroscopic observation. Oscula not visible. Numerous barnacles are embedded in the sponge tissue, with only their openings free (Fig. 7B).

Skeleton. The ectosomal skeleton is an irregular reticulation of rectangular meshes 120–150 µm, up to 190–250 µm in diameter, formed by fibres 20–40 µm thick (Fig. 7B, C). Fibres are cored by 4–6 spicules. In the well-preserved parts of the sponge, a thin dermal membrane covers the surface. When the membrane is damaged, the sponge surface is microhispid due to protruding fibres. The choanosomal skeleton (Fig. 7D) is irregular, formed by primary multispicular (approximately 10 spicules) fibres, about 60 µm thick, directed towards the surface; secondary fibres are 20–35 µm in diameter. Secondary and primary fibres create an irregular reticulation of more or less circular meshes 170–300 µm across. Spongin is not abundant.

Spicules. Megascleres are oxeas slightly curved, with sharp tips (Fig. 7E, F), 97 - (111.6 ± 6.7) - 122.4 × 2.6 - (4.5 ± 1.2) - 5.2 µm.

Figure 7. 

Amphimedon anastomosa sp. n. A The holotype just after collection B Sponge surface with the round opening of a symbiotic barnacle C ectosomal skeleton D choanosomal skeleton E oxeas F magnification of an oxea tip.

The name refers to the habitus of the sponge, characterised by anastomosing branches.

The species described here may be attributed to the genus Amphimedon due to its skeleton characteristics. Out of the 54 species of Amphimedon hitherto described (van Soest et al. 2016), only two (A. denhartogi de Voodg, 2003 and A. elastica (Kieschnick, 1898) are present in Indonesia, whereas 30 have been recorded in the Indo-Pacific region. Amphimedon denhartogi and A. elastica differ from A. anastomosa sp. n. in their skeletal organisation and general morphological characters. The species A. denhartogi is green in life, like A. anastomosa sp. n., but it has an erect, flabellate shape and star-shaped oscula; moreover, it has strongyles as spicules. In contrast, A. elastica is a single-tube yellow-brownish sponge with a wide apical osculum (11 mm in diameter) and smooth surface; spicules are oxeas of 90–100 µm. Also, the other Indo-Pacific species show significant differences with A. anastomosa sp. n.; A. aculeata Pulitzer-Finali, 1982 is a vase-shaped sponge with conical projections on the surface and strongyles as spicules, whereas A. aitsuensis (Hoshino, 1981), described from Japan, is a massive sponge, grey in colour and with oxeas of two distinct size categories (thick oxeas of 132–148 × 7–9 µm and thin oxeas of 115–135 × 4–6 µm). Amphimedon alata Pulitzer-Finali, 1996 has oxeas of 100–130 × 7–11.5 µm and peculiar, small, wing-shaped toxas (11–50 µm); A. brevispiculifera (Dendy, 1905) is an erect sponge light-brown in the dry state; it is digitate or flabellate, with evident large oscula; it differs from A. anastomosa sp. n. also for its stout primary fibres 164 µm thick. The two species A. chinensis and A. flexa have been described by Pulitzer-Finali (1982) from Hong Kong; A. chinensis differs from the new species for the orange colour, the presence of oscula arranged in a single row and the larger oxeas (125–145 × 8–9.5 µm), while A. flexa is plurilobate with oscula on top of the lobes; its primary fibres, slightly thicker than those of the new species, create larger meshes from 300 to 900 µm across. The species A. chloros Ilan et al., 2004 is green, like A. anastomosa sp. n., but cushion-shaped, with oxeas that usually become strongyloxeas. In contrast, A. conferta Pulitzer-Finali, 1996 is sub-cylindrical, brown in life, cream in the dry state, with ectosomal tracts 75 µm in diameter; spicules are oxeas longer and thicker (140–160 × 7–9 µm) than those of A. anastomosa sp. n., with frequent stylote modifications. Amphimedon cristata Pulitzer-Finali, 1996 is sub-cylindrical, violet in colour and rigid, with an apical osculum; it has large oxeas (230–370 × 11–18 µm) with blunt extremities. Other three species of Amphimedon have been described by Helmy and van Soest (2005) from the Red Sea: A. dinae, A. jalae, A. hamadai. Amphimedon dinae is a brown, massive sponge with oscula 2-4 mm wide and very thin and short oxeas (52–61 × 1–1.5 μm); A. jalae is massive, cushion-shaped, with large oxeas (100–170 × 4–6 μm) and choanosomal rounded meshes of 600–800 μm. Amphimedon hamadai is brown, irregularly lobated, with very short oxeas (48–60 × 2–3 μm), while A. delicatula (Dendy, 1889) is erect, bushy, yellow in colour and with stout fibres 126 µm thick and very slender, slightly curved oxeas (98 by 3.5 µm). Amphimedon lamellata Fromont, 1993 is a lamellate, erect sponge, pale pink in colour; with a reticular choanosomal skeleton and two types of oxeas differing in thickness (111–130 × 2.5–4.4 µm and 105–126 × 1.3–2.3 µm); A. massalis (Carter, 1886) is massive, yellow in the basal portion, dark brown-red on the surface, with vents “on monticular elevations” and oxeas measuring 155 × 6 µm. Amphimedon navalis, A. rubida, A. rubiginosa and A. spinosa have been described by Pulitzer-Finali (1993) from Kenya. Amphimedon navalis is a cushion-shaped sponge, dark blue and violet in colour, with blunt oxeas (160–210 × 11–15 µm); A. rubida is cylindrical, red brownish, with meshes of 220–360 µm across and oxeas measuring 185–230 × 11.5–18 µm. Amphimedon rubiginosa has a massive shape with elevated oscula and a skeletal organisation with ill-defined plurispicular tracts. Amphimedon spinosa has a tubular shape and fibres cored by single spicules, while A. paraviridis Fromont, 1993 is encrusting or ramose, green-olive in life, with primary fibres of 50–160 µm and secondary of 20–50 µm, thicker than those of the new species. Moreover, abundant oxeas (133–151 × 3.9–8.0 µm) are scattered in between the fibre reticulation (absent in A. anastomosa sp. n.). Amphimedon queenslandica Hooper & van Soest, 2006 is a blue-grey and green sponge with an encrusting base from which lobate or digitate portions rise. Unlike the new species, it has unispicular fibres. A. robusta (Carter, 1885) is a branching-digitate, orange sponge with oscula located on one side; A. rudis Pulitzer-Finali, 1996 is violet-brownish, with blunt and very stout oxeas (360–420 × 10–12.5 µm). Amphimedon strongylata Pulitzer-Finali, 1996 is sub-cylindrical, grey in colour, with strongyloxeas as megascleres; A. subcylindrica (Dendy, 1905) is a cylindrical sponge with reptant habit; it has a smooth surface and oscula with prominent rims; its fibres are cored by a high number of spicules (slightly longer (140 × 8 µm) oxeas), without visible spongin. Amphimedon sulcata Fromont, 1993 is a small, globular sponge with oxeas of 122–153 × 3.0–5.3 µm and C-shaped sigmas as microscleres. Finally, A. zamboangae (Lévi, 1961), which is green in colour, has a velvety surface, thick fibres (130 µm) and two types of oxeas (120–150 × 4–6 µm and 120–130 × 3 µm).

“Amphimedon differ from other Niphatidae in having an optically smooth, but microscopically microtuberculate fibrous superficial skeleton, usually with abundant spongin, and lacking microscleres” (Hooper and van Soest 2006). Because of the slight differences between Amphimedon and Niphates (Desqueyroux-Fáundez & Valentine 2002), all the Indo-Pacific species of the latter genus were also checked. All these species of Niphates differ from the new species in shape, colour and skeletal organisation. The most similar species, in terms of the branched shape, is N. aga (de Laubenfelds, 1954), but it has a confused ectosomal skeleton and longer oxeas (175–180 µm). Amphimedon anastomosa sp. n. is well characterised by its growth form and colour. Since no species in this vast geographic area matches with our specimen, we are justified to erect a new species.

Holotype: MSNG 60139, PH-47, 17/01/2005, Tiwoho (Bunaken Island), 20 m depth.

Lamellate, azure-violet sponge, with differentiated inhalant and oscular faces. Skeleton is a regular reticulum of primary and secondary fibres, with superficial brushes hispidating the surface; megascleres are straight and sinuous oxeas. Microscleres are sigmas.

The sponge is a thin, irregular, folded lamina, attached to the substrate in few points (Fig. 8A); its rim is more or less rounded, not regular (Fig. 8B). The holotype consists in alcohol-preserved fragments, collected from a bigger specimen (Fig. 8A, B). The largest observed specimen is approximately 8 × 4 cm long and 2 mm thick. The colour in life is azure-violet in the part exposed to light and beige on the shadowed side (Fig. 8B). The sponge becomes white-bluish when dried. Consistence soft, slightly elastic. The aspect of the two sides of the laminar sponge is different: roundish vents, 700–1,300 µm in diameter, most probably acting as oscula, are concentrated on the excurrent side (Fig. 8C); on the opposite side, a thin dermal membrane, pierced by numerous pores, covers several smaller apertures, not visible to the naked eye (Fig. 8D). In the dried state, spicule brushes and small ridges (made by tracts of tangential oxeas connecting the brushes) create a microconulose surface, visible also to the naked eye, in both sides of the sponge.

Skeleton. The ectosomal skeleton is a reticulation of multispicular tracts (30–60 µm thick) forming polygonal (mostly quadrangular) meshes 340–900 µm in diameter, with brushes of spicules at the nodes (Fig. 8D). The choanosomal skeleton is a not very regular reticulation, with elongated, almost rectangular meshes 400–800 µm across and empty spaces. The spicule tracts may be divided into ascending primary tracts, 55–100 µm thick, and secondary tracts, 25–35 µm thick, with a more or less transverse arrangement. The extremities of the ascending tracts protrude through the surface, forming brushes (Fig. 8D). Very numerous pigmented (green) cells and abundant spicules, both megascleres and microscleres, are dispersed in the ectosome and choanosome.

Spicules. Oxeas slightly curved or sinuous, rarely straight, with acerate tips (Fig. 8E). They measure 150.8 - (163.37 ± 7.0) - 176.8 × 2.5 - (3.7 ± 1.1) - 5.2 µm. Sigmas C-shaped, sometimes with a part of the shaft almost straight (Fig. 8F). They measure 13 - (17.0 ± 3.18) - 23.4 µm × 1 µm.

Figure 8. 

Niphates laminaris sp. n. A holotype in situB, C holotype freshly collected showing the exhalant side of the sponge D sponge skeleton on the exhalant side with in evidence the choanosomal ascending tracts protruding through the surface and the vents E sinuous and straight oxeas F sigma.

The name refers to the lamellate shape of the sponge.

The new species clearly belongs to the family Niphatidae for the presence of multispicular fibres in the ectosome and to the genus Niphates for the skeletal organisation. The genus Niphates includes sponges with “Surface conulose to spiny [….] produced by primary longitudinal fibres ending on surface” (Desqueyroux-Faúndez and Valentine 2002). The ectosomal skeleton is a tangential network of secondary fibres, obscured by protruding tufts of primary fibres. Microscleres are rare sigmas (Desqueyroux-Faúndez and Valentine 2002). However, other species of the genus (e.g. Niphates nitida Fromont, 1993) have a smooth surface as the new species.

Niphates laminaris sp. n. is characterised by a non-spiny, rather irregular, microconulose surface and by a choanosomal skeleton with a reticulation of primary and secondary tracts. Microscleres are numerous. In the Indo-Pacific area, only N. nitida has sigmas. However, N. nitida is a sponge with repent habit, with oscula located at the top of small erect lobes; a choanosomal fibrous reticulation with round or triangular meshes (104–146 µm) and oxeas measuring 128 × 5.6 µm. Therefore, it substantially differs from Niphates sp. n; all other Niphates in the area differ from the new species for the absence of sigmas and for other significant features listed below. Niphates olemda (de Laubenfelds, 1954) is a blue, or pink tubular sponge with small oxeas (92–100 × 2–3 µm), while N. aga (de Laubenfelds, 1954) is ramose with superficial projections, a confused ectosomal skeleton and straight and large oxeas (175–180 × 5 µm). Niphates cavernosa Kelly-Borges & Bergquist, 1988 is a massive, creeping and branching sponge, violet in life, with two categories of oxeas differing in thickness (oxeas I: 5–10 µm thick; oxeas II: 2–4 µm); N. furcata (Keller, 1889) is green, erect, branching, with rather short oxeas (100 × 12 µm). Niphates hispida Desqueyroux-Fáundez, 1984 is a hard and incompressible sponge with very small oxeas (60-80 × 2-4 µm), consisting of a series of coalescent, cylindrical tubes arising from a massive common base. Niphates mirabilis (Bowerbank, 1873) is an ochre-pinkish sponge with a unispicular ectosomal reticulation, while N. obtusispiculifera (Dendy, 1905) is a branching, cylindrical sponge with strongyles as megascleres. Niphates plumosa (Bowerbank, 1876) is fawn-coloured and has a peculiar, stipitate and fan-shaped growth form with only oxeas as spicules. Niphates rowi Ilan et al., 2004 is the species most similar to the new species. Its ectosomal skeleton is a reticulation of fibres creating quadrangular meshes which are smaller than those of Niphates laminaris sp. n. (70–115 µm). In addition, the choanosomal reticulation of N. rowi has rectangular meshes which are smaller (115–200 µm) than those of Niphates laminaris sp. n., whereas the oxea size is similar (115 - (140) - 170 × 5.5 - (6.5) - 7.5 µm). In conclusion N. rowi, which is an encrusting sponge, differs from Nipahtes laminaris sp. n. in the growth form, the absence of sigmas and sinuous oxeas and in the size of the ectosomal and choanosomal meshes.

Holotype: MSNG 60140, PH-41, 14/01/2005, Timur (Bunaken Island), 22 m depth.

Lobate, white sponge with oscular cavities at the top of the lobes. Thin armoured surface with sand and foreign spicules. Slightly fasciculated fibres, not very dense.

Massive, lobate sponge with flush, roundish oscular cavities (about 1.5 cm) where the excurrent canals converge, located at the top of the lobes (Fig. 9A). The deposited holotype consists of fragments 3 × 1.5 cm, coming from a larger specimen approximately 15 cm across (Fig. 9A).

The colour in life is white outside (Fig. 9A) and cerulean inside; it becomes light cerulean after collection and beige after preservation in alcohol. Surface characterised by numerous small conules, 0.5–1 mm high and 2 mm apart, united by ridges (Fig. 9A, B). Consistence soft, but elastic, difficult to tear apart.

Skeleton. The surface is covered by a thin reticulation of sand and foreign spicules, forming regular, more or less circular, meshes 100 µm in diameter (Fig. 9C), well visible in the stereo-microscope. The density of the fibres is moderate. The primary fibres of the choanosome are slightly fasciculated (Fig. 9D), about 80 µm thick and cored with foreign debris and a few foreign spicules. The secondary fibres are thinner (20 µm in diameter) and free from inclusions (Fig. 9D). The size of the ovoid meshes ranges from 50 × 80 to 57.5 × 115 µm; a few smaller meshes, 30 × 55 µm, are also present. Filaments, 2.5 µm thick, are numerous and dense.

Figure 9. 

Psammocinia alba sp. n. A the sponge in situB a small conule at SEMC reticulation made of sand grains and foreign spicules D primary fibres cored with foreign material and, on the right, secondary fibres free from inclusions.

Referring to the white colour in life.

Our species is attributed to Psammocinia due to the presence of a surface armoured by sand and foreign spicules and to the reticular skeleton of primary and secondary fibres.

According to van Soest et al. (2016), 25 species of Psammocinia are known in total. Most of them have been described from New Zealand and South Korea and only one from Brazil.

Psammocinia bulbosa Bergquist, 1995 from New Caledonia and P. lobatus Sim & Lim, 2002 from Korea are the most similar species to Psammocinia alba sp. n. Psammocinia bulbosa is a massive, repent sponge with quite long oscular fistules. Its surface is covered by small conules 0.5–1 mm high and has a sandy crust up to 1 mm thick. The skeleton is formed by primary fibres giving rise to columns up to 700 µm long and secondary fibres 30–50 µm in diameter. The main differences to our species are the presence of fistules, a distinctive characteristic of P. bulbosa, and thicker fibres. Psammocinia lobatus, lobate in shape, has a surface covered by conules 1–2 mm high and 2–5 mm apart. Both primary and secondary fibres (60–10 µm thick) are comparable in size with our species. The main differences to P. alba sp. n. are the colour (dark brown, black), the presence of sharp conules and the small amount of foreign material present in the fibres. From New Zealand, the following species have been described: P. beresfordae Cook & Bergquist, 1996, formed by a compact base with broad-based fistules with an apical osculum 3–7 mm in diameter and primary fibres 120 µm thick; P. verrucosa Cook & Bergquist, 1996, a small, massive sponge with a very characteristic surface with rounded lamellae supported by skeletal fibres and a reticulate pattern; P. hirsuta Cook & Bergquist, 1998, formed by a coalescent group of digitate structures or lobes, with long, cylindrical fistules and a thick (400 µm) superficial sand layer; P. charadrodes Cook & Bergquist, 1998, a massive sponge with very long, rounded conules and very thick (till 1086 µm) primary fibres; P. papillata Cook & Bergquist, 1998, a massive, compact sponge with a coarsely conulose surface and both primary and secondary fibres thicker than in Psammocinia alba sp. n.; P. perforodosa Cook & Bergquist, 1998, a massive, compact sponge without conules, with a folded surface (800 µm thick) armoured by sand, foreign spicules and rocky fragments; P. maorimotu Cook & Bergquist, 1998, a lobate sponge with oscula on top, a surface with grooves and ridges and primary fibres with a thickness of 349 µm. From South Korea and China, the following species have been described: P. conulosa Lee & Sim, 2004, a massive sponge with ectosomal membrane covered by sand but devoid of circular meshes, oscula scattered and sharp conules 2–4 mm high; P. ulleungensis Lee & Sim, 2004, dark grey in colour, with a smooth surface and thick, slightly fasciculated, primary fibres (100–300 µm); P. mammiformis Sim, 1998, a massive, grey or purple coloured sponge, covered with mammiform protuberances and with very thick choanosomal fibres 550–900 µm; P. mosulpia Sim, 1998 mainly differs from P. alba sp. n. for its crust of sand and foreign spicules not organised in circular meshes; P. jejuensis Sim, 1998, characterised by tick fibres (up to 470 µm) and by filaments with large terminal knobs (12–20 µm in diameter); P. gageoensis Sim & Lee, 2001, has no detritus in the fasciculated primary fibres. Both P. samyangensis Sim & Lee, 1998 and P. wandoensis Sim & Lee, 1998 differ from P. alba sp. n. mainly in the thickness of the secondary fibres. Finally, P. rubra Sim & Lee, 2002 differs from P. alba sp. n. for its red colour and the larger size (up to 320 µm) and colour (reddish-brown) of the fibres.

The other species of Psammocinia have a particular morphology, very different respect to Psammocinia alba sp. n.; P. arenosa (Lendenfeld, 1888) and P. hawere Cook & Bergquist, 1996 are cup-shaped sponges. Psammocinia halmiformis (Lendenfeld, 1888) is irregularly lamellate and P. vesiculifera (Poléjaeff, 1884) is a tube sponge. Psammocinia amodes Cook & Bergquist, 1998 is a spatulate sponge with a thin, semi-cylindrical basal portion for anchoring to the substrate, while P. bergquistae Sim & Lee, 2001 has a thumb shape and secondary fibres, forming a secondary web.

Due to the difficulties to differentiate, in some cases, species of the genus Psammocinia from other taxa of the family Irciniidae, we also examined the species belonging to Ircinia and Sarcotragus from the Indo-Pacific area. All these species are different from Psammocinia alba sp. n. in morphology, fibre thickness, and structure (see below).

The incorporation of foreign material can play several roles in sponge growth. Usually, this behaviour is explained just as strengthening of the sponge tissue, but other roles could be considered, e.g. the enhancement of sponging fibre production (Cerrano et al. 2007).

Holotype: MSNG 60141, PH-44, 15/01/2005, Timur (Bunaken Island), about 20 m depth. Paratype: MSNG 60142, BKA 25, 12/09/2014, Yellow coco (Bangka Island), about 20–25 m depth.

BU-590, 27/07/2004, Timur (Bunaken Island), 25 m depth. INDO-431, 13/05/2005, Jetty (Siladen), depth not stated, N01°37'38.8"; E124°48'00.8".

Soft and elastic cup-shaped Ircinia with a large, central cavity; conulose surface; heavily fasciculated fibres with foreign material.

The sponge is columnar, reminding of a partially hollow cylinder, due to the presence of a wide central cavity (Fig. 10A). It may be as high as 80 cm, with a wall 1–2 cm thick. The holotype is a fragment approximately 4.5 × 2 cm. The external colour is light brown with greenish tinges on the conules and on the rim of the cavity (Fig. 10A). The freshly collected sponge is beige inside (Fig. 10B). Alcohol-preserved specimens remain almost the same in colour. The sponge surface is strongly conulose, with rounded or slightly flattened conules 2–4 mm high (Fig. 10A, B). The oscula (3–5 mm in diameter) are present in the inner part of the central cavity. Consistence is soft and elastic, but the sponge is difficult to tear off.

Skeleton. The choanosomal skeleton is formed by primary fibres cored by foreign spicules (Fig. 10C, D), 180–350 µm in diameter and heavily fasciculated (Fig. 10C). They are connected by secondary fibres 50–80 µm in diameter, sometimes cored by single spicules. The fibres form a reticulation of elongated meshes, 100–150 µm in size, and cribrose plates (Fig. 10C). Very abundant thin filaments are mainly organised in tracts (Fig. 10E), but also dispersed in the mesohyl. They are 3-5 µm thick and present an oval or rounded terminal knob (7.5–10 µm in diameter) (Fig. 10F).

Figure 10. 

Ircinia colossa sp. n. A specimen BU-590 in situB portion of the holotype C fasciculated fibres D primary fibres with foreign spicules E filaments organised in tracts F filaments with a terminal knob in evidence.

The name refers to the sturdy and large size of the sponge.

The studied specimens are attributed, according to Cook and Bergquist 2002, to the genus Ircinia for the strong fasciculation of fibres, with foreign material inside and the presence of filaments. There are more than 40 species of massive, encrusting, digitate or branching Ircinia in the Indo-Pacific area (van Soest et al. 2016), which differ from Ircinia colossa sp. n. in morphology, fibre thickness and quantity of external debris in the skeleton.

Only two species of Ircinia, living between 10 and 40 m depth in the temperate water of South-East Australia, show a central cavity: I. caliculata (Lendenfeld, 1888) and I. rubra (Lendenfeld, 1889). Ircinia caliculata differs from I. colossa sp. n. in the general morphology, colour, and organisation of the fibres. It has the rim of the cup bent outwards; the internal part of the cavity with small conules 2–3 mm high. The external part of the sponge presents digitate processes about 10 mm thick. The colour is dark-red brownish. It has fasciculated fibres full of sand grains. Ircinia rubra differs from I. colossa sp. n. in the general shape and fibre size. It is a small, conical, pedunculate sponge with a central cavity. All the fibres are full of debris and foreign spicules and the secondary fibres, 100 µm in diameter, are thicker than those of Ircinia colossa sp. n.

We also examined species belonging to the genus Sarcotragus; none of them fits with the characters of the new species. Sarcotragus aliger (Burton, 1928) is clavate, cylindrical with an apical osculum and fibres 80 µm in diameter, while S. australis (Lendenfeld, 1888) is a massive red sponge. Sarcotragus coreanus (Sim & Lee, 2002) is massive to encrusting, beige in colour; S. gapaensis Sim & Lee, 2000 is subspherical, dark brown to black, with big primary fibres 280–530 µm in diameter. Sarcotragus maraensis Sim & Lee, 2000 is globular with sharp conules 2–8 mm high and an ivory and purple colour. Sarcotragus myrobalanus (Lamarck, 1814) is an ovoid sponge with a long peduncle, brown-reddish in colour; S. tuberculatus (Poléjaeff, 1884) has fibres that often do not ramify and its surface, greyish in colour, is covered by rounded tubercles; filaments are roundish and 55 µm in diameter.

Ircinia colossa sp. n. is frequent in the Bunaken Park and the nearby Bangka Island (North Sulawesi); the paratype was found with other relatively large specimens (50 cm high or more) near a hot vent flowing from a sandy bottom (Bertolino et al. 2017).

This species is probably present also throughout northern Australia and Papua New Guinea (J. Hooper, pers. comm.). Molecular analysis, compared against sequences made by Pöppe et al. (2011) for Ircinia and Psammocinia species from northern Australia, would be very useful to confirm if Ircinia colossa sp. n. and P. alba sp. n. are also present in Australia.