Aaptos lobata Calcinai, Bastari, Bertolino & Pansini

Calcinai, Barbara, Bastari, Azzurra, Bavestrello, Giorgio, Bertolino, Marco, Horcajadas, Santiago Bueno, Pansini, Maurizio, Makapedua, Daisy M. & Cerrano, Carlo, 2017, Demosponge diversity from North Sulawesi, with the description of six new species, ZooKeys 680, pp. 105-150 : 105-106

Aaptos lobata Calcinai, Bastari, Bertolino & Pansini sp. n. Figure 2

Material examined.

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.

Other material.

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".

Diagnosis.

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.

Description.

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.

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.

Etymology.

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

Remarks.

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.