Corvospongilla siamensis Manconi & Ruengsawang

Ruengsawang, Nisit, Hanjavanit, Narumon Sangpradub Chutima & Manconi, Renata, 2012, Biodiversity assessment of the Lower Mekong Basin: A new species of Corvospongilla (Porifera: Spongillina: Spongillidae) from Thailand, Zootaxa 3320, pp. 47-55 : 49-50

Corvospongilla siamensis Manconi & Ruengsawang nov. sp.

Figures 1–4

Material. Holotype MSNG 56533, Ban Huai Sai (16˚46ˏ20.40˝N, 102˚42ˏ48.22˝E) type locality, Pong River, Lower Mekong Basin, Thailand, leg. Nisit Ruengsawang, 12.II.2008. Paratype MSNG 56533a, Ban Huai Sai, leg. Nisit Ruengsawang, 12.II.2008.

Comparative materials. Corvospongilla burmanica , BMNH 82.3.22.1–3, box 6, dry, type, DTRG FW420 schizotype, Burma; C. burmanica (?), BMNH 86.10.29.1, DTRG FW 636, River Kuano, India; C. caunteri , BMNH 14.11.24.27 ex-ZEV 4776/7, paratype, DTRG FW637, schizotype, Lucknow, India; C. lapidosa , BMNH 0 8.2.11.1, paratype, DTRG FW638, schizotype, River Godavery Nasik, India; Corvospongilla loricata , ZMB 2093 SE325-SE37–41, type, fragment DTRG FW511 locality unknown, Africa; C. mesopotamica MSNG 51766, holotypes, DTRG FW574, schizotype, River Diyala, Iraq; C. thysi , MRAC 1311, type, DTRG FW472, schizotype, Lake Barombi-ma-Mbu, Cameroun, W-Africa; C. ultima , BMNH 14.11.24.29 ex-ZEV 4906/7, DTRG FW639, fragment, India; C. ultima var. spinosa , BMNH 14.11.24.30 ex-ZEV 5106/7, DTRG FW640, Satara District, India; C. volkmeri , BMNH 89.9.25.10, schizoparatype, ex-MCN 86, DTRG FW642, Lagoa Redonda, Sousa, Paraíba State, Brazil; C. zambesiana , BMNH 1906.2.28.2, 13 IIIC, DTRG FW623 R. Zambezi, SE-Africa.

Description. Holotype massive 14 x 11 cm in diameter, 0.5–5 cm in height with lobes up to 3–4 cm in height ( Fig. 2 A). Growth form from thin crusts to massive in flourishing specimens with body size dimensions up to 16 cm in diameter. Colour light brown, greenish to emerald green in vivo in the same specimen, light brown to brown in ethanol. Consistency rigid, hard with increasing hardness from surface to the basal portion, fragile in vivo, due to the low amount of spongin in the skeleton. Basal spongin plate notably developed, with sessile gemmules. Surface notably irregular and hispid, conulose, with conules supported by short ascending pauci- to multi-spicular tracts. Conules 1–2.5 mm in height, 1–1.5 mm apart. Oscules chimney-shaped (0.2–0.5 cm in diameter) apical and usually single at the tips of lobes ( Fig. 2 B). Ectosomal skeleton with no special architecture (triangular to polygonal paucispicular meshes) except for ascending pauci- to multi-spicular tracts supporting conules ( Fig. 3 A). Choanosomal skeleton as an alveolar (isotropic) network of megascleres with paucispicular (up to 6 spicules) polygonal meshes (89–213 µm in diameter), and ascending pauci- to multi-spicular tracts supporting conules ( Fig. 3 B). Megascleres strongyles (126–245 x 13–26 µm) frequently with slightly inflated tips, extremely abundant with scattered small tubercles (granules) except for tips or with shaft entirely covered of tubercles up to the tips ( Figs 2 C, 3C, D). Less frequent acanthostrongyles with few spines scattered up to the tips, among the small tubercles. Density of tubercles and spines notably variable. Rare smooth strongyles also present. Strongyles sometime xshaped or with tips slightly inflated or rarely with swellings along the shaft as malformations. Rare stout, smooth oxeas (160–171 x 9–14 µm, n = 4) with tips abruptly pointed also present ( Fig. 3 C). Microscleres micropseudobirotules quite abundant, scattered in the choanosomal skeleton, typical of the genus, with smooth, variably bent shaft (19–51 x 2–2.5 µm) bearing distal smooth pseudorotules (9–19 µm in diameter) with variably long, bent hooks (4–6) ( Fig. 3 E). Gemmules exclusively sessile, not abundant at the sponge basal portion, strictly adhering to the basal spongin plate singly or in small groups (2–5) sharing gemmular cages with fused walls ( Fig. 4 A). Gemmular cage hemispherical (865–1160 µm in diameter) with thick wall (107–113 µm in thickness) of extremely scanty compact spongin in small laminae joining abundant strongyles arranged in a notably dense mosaic-like multilayer. Strongyles of the cage belong to different categories, from stout, large, granulate (tubercled) strongyles (107–190 x 15–27 µm, n = 25) very similar to skeletal megascleres, to bent and tubercled strongyles (27–49 x 7–14 µm, n = 15), to bent acanthostrongyles (29–49 x 6–9 µm, n = 5) up to boomerang-shaped, or ring-like (17 µm in diameter, n = 2) and flat button-like (16–27 µm in diameter, n = 4), armed by acute spines sometimes grouped ( Fig. 4 B). Gemmular theca enveloped by the cage but not joined to it (cage and theca are easily detachable from each other), subspherical (589 x 650 µm in diameter) to suboval (424 x 814 µm in diameter) ( Fig. 4 C, D) of almost compact spongin with sublayers (up to 5) supported by small gemmuloscleres tangentially embedded ( Fig. 4 E, G, H). Pneumatic layer absent; only rare, small areas of spongin chambers are present, scattered within the sublayers of laminar spongin. Foramen single, apical or lateral with a short simple collar surrounded by slightly chambered spongin ( Fig. 4 F). Gemmuloscleres short acanthostrongyles (32– 50 x 7–14 µm, n = 25) from straight to boomerang-shaped, ring-shaped to flat (button-like) with ornamentations ranging from tubercles scattered along the shaft to large acute spines mostly at the tips ( Fig. 3 F); also smooth spherules rarely present. Brooded larvae present. Larval acanthoxeas (128–139 x 5 µm, n = 3) fusiform, slender, straight, with scattered small, acute spines more dense towards the tips.

Etymology. The specific epithet is derived from the ancient name of Thailand, formerly known as Siam.

Geographic distribution. Known until now exclusively from the type locality ( Fig. 1 ).

Habitat. Sponges in dense populations along the river bank at 0.5–2.0 m of depth in quite transparent waters, generally in shaded areas. Associated organisms: diatoms, insects, molluscs, bryozoans.

Figures

FIGURE 1. Biogeographic pattern of the genus Corvospongilla (modified from Manconi & Pronzato, 2002, 2004). The type locality of Corvospongilla siamensis at Ban Huai Sai (16 ˚ 46 ˏ 20.40 ˝ N, 102 ˚ 42 ˏ 48.22 ˝ E) (Pong River, Lower Mekong Basin, Thailand) is indicated by an arrow.

FIGURE 2. Corvospongilla siamensis. A, Holotype MSNG 56533 from the Pong River (Lower Mekong Basin, Thailand). B, Detail of a chimney-like lobe with apical oscule and conulose surface. C, Spicular complement. Strongyle and micropseudobirotule from the skeletal network, and strongyle from the gemmular theca.

FIGURE 3. Corvospongilla siamensis. Holotype MSNG 56533 from the Pong River (Lower Mekong Basin, Thailand). Micrographs (SEM) of the spicular complement. A, Skeletal alveolate network with ascending plurispicular tracts (arrows) to support conules at the surface (lateral view); B, Detail of alveolate skeleton of strongyles and micropseudobirotules (inset); C, Skeletal megascleres, as strongyle with microspined surface (inset, right), and tips of the rare tubercled oxeas (inset, left); D, Apices variably shaped of strongyles and a microsclere; E, micropseudobirotules entirely smooth with pseudobirotules armoured by recurved hooks; F, strongyles, with tubercles and spines, shared by gemmular theca and gemmular cage.

FIGURE 4. Corvospongilla siamensis. Holotype MSNG 56533 from the Pong River (Lower Mekong Basin, Thailand). Micrographs (SEM) of gemmules. A, Gemmules of the sessile morph in a cluster sharing the gemmular cage strictly adhering to the basal spongin plate. Each hemispherical cage envelopes one gemmular theca; B, Strongyles variably shaped at the outer surface of the gemmular cage, typical button-like gemmuloscleres are indicated by arrows; C, D, Gemmular theca variably shaped, bearing tangentially gemmuloscleres embedded in compact spongin; E, Gemmular theca surrounded by the not adhering stout spicular cage (cross section); F, Foramen with compact and chambered spongin armed by a few gemmuloscleres; G, Gemmular theca (cross section) of sublayered compact spongin protecting the mass of totipotent cells; H, Detail of the gemmular theca (cross section) of compact sublayered spongin armed by gemmuloscleres as tangential strongyles with spiny tips.