Plakinastrella globularis, Domingos, Celso, Moraes, Fernando & Muricy, Guilherme, 2013

Domingos, Celso, Moraes, Fernando & Muricy, Guilherme, 2013, Four new species of Plakinidae (Porifera: Homoscleromorpha) from Brazil, Zootaxa 3718 (6), pp. 530-544 : 538-541

Plakinastrella globularis sp. nov.

( Figs. 5 & 6 )

Specimens examined (7). Holotype: MNRJ 5980. Paratypes: MNRJ 15460, 15461, 15462, 15463, 15464, all five and the holotype from off Salvador, REVIZEE Sta. R4-01 (13.075ºS, 38.392ºW), Bahia State, Brazil, 91 m depth, Navio Oceanográfico Astro Garoupa coll., 23 June 2002; MNRJ 6133, Almirante Saldanha Seamount, REVIZEE Sta. Y 2 (22.382ºS, 37.5788ºW), Rio de Janeiro State, Brazil, 270 m depth, Navio Oceanográfico Astro Garoupa coll., 12 June 2002.

Specimens examined for comparison. Plakinastrella microspiculifera : MNRJ 2135, 2164, 3598, all from Atol das Rocas; MNRJ 4749, São Pedro e São Paulo Archipelago, Brazil.

Plakinastrella onkodes : ZMAPOR 9725, Santa Marta, Colombia; USNM 30135, Puerto Rico.

Diagnosis. Plakinastrella with globular shape, dark blue color in vivo, diods in two categories, triods, calthrops, non-tuberculate microrhabds, reticulate choanosomal skeleton, subectosomal lacunae and a double tangential ectosomal reticulation.

Description. Shape globular, irregular. Size varying from 4 x 3.5 cm wide by 3.5 cm high to 6 x 6 by 5 cm ( Fig. 5 A). External color dark blue in vivo according to the original labels, becoming grayish-brown with dark patches after fixation. Internal color slightly lighter than the external. Surface smooth but uneven, irregular, inlaid with calcareous debris. Oscules randomly dispersed, visible after fixation, 1 mm in diameter. Consistency firm, incompressible.

Skeleton. Tangential ectosomal skeleton reticulate, with multispicular tracts forming a double reticulation of circular meshes ( Fig. 5 B): (1) 20-29-40 µm (n=60), and (2) 40-85-130 µm (n=60). The small diods are arranged perpendicularly to the surface, forming a palisade ( Fig. 5 D). Ectosomal lacunae absent. Subectosomal lacunae abundant, elongate, 50-105-350 µm ( Fig. 5 C; n=60). Choanosomal skeleton dense, reticulate ( Fig. 5 C). Canals with wide size variation are abundant in the mesohyl.

Spicules. Diods thin, sinuous, smooth, with central bent slightly or heavily deformed and acerate ends. Some diods are curved near one or both ends. At least two categories of diods can be distinguished: (1) small, thin, with central bent well marked and acerate ends, concentrated at the ectosome ( Fig. 6 A): 11-20-26 / 1-1.5-2 µm (n=60); and (2) large, with central bent almost smooth ( Fig. 6 B): 40-84-130 / 1-3.1-6 µm (n=120).

Triods ( Fig. 6 C) rare, straight, regular, smooth, with acerate ends: 39.5-55.6-76.6 / 2-3-5 µm (n=60).

Calthrops ( Fig. 6 D) common, straight, regular, smooth, with acerate ends: 24.7-37.1-54.3 / 2-6.5-8 µm (n=60). Microrhabds rare, irregular, often curved in the center ( Fig. 6 E): 4-5.2-6 µm (n=60).

Spheres smooth or slightly rugose ( Fig. 6 F): 1-2.4-8 µm (n=60).

Habitat and ecology. The specimens were collected between 90 and 270 m depth and incorporate sediment and polychaete tubes.

Distribution. Known only from the continental shelf and seamounts in Bahia and Rio de Janeiro States, Brazil ( Fig. 1 ).

Taxonomic remarks. Plakinastrella globularis sp. nov. is most similar to P. microspiculifera , with which it shares the presence of subectosomal cavities, a double tangential ectosomal reticulation, choanosome vaguely reticulated and the size of diods. However, P. microspiculifera greatly differs from the new species by the encrusting shape, gray to black color, shape and size of triods and calthrops, absence of ectosomal palisade of small diods, and absence of microrhabds.

Plakinastrella onkodes is similar to the new species in the firm consistency, presence of subectosomal cavities, and vaguely reticulated choanosomal skeleton. It differs from Plakinastrella globularis sp. nov. by the nonglobular shape, dark brown color, single-meshed tangential ectosomal reticulation, size of diods, triods and calthrops (80–180, 22–40, and 55–90 µm long, respectively), and absence of microrhabds.

Plakinastrella mammilaris Lendenfeld 1907 is also globular in shape, but it has abundant mammiliform projections with apical oscules, brown color, much larger calthrops (150–280 µm), and triods are absent.

Plakinastrella globularis sp. nov. differs from all other species of Plakinastrella by its globular shape, dark blue color, double-meshed tangential ectosomal reticulation, and the presence of non-tuberculate microrhabds. Etymology. The name globularis refers to the globular shape of the specimens.

Figures

FIGURE 1. Collection sites of the four new species of Plakortis. Orange, Plakortis petrupaulensis sp. nov. (São Pedro e São Paulo Archipelago); blue, Plakortis spinalis sp. nov. (Fernando de Noronha Archipelago); yellow, Plakortis potiguarensis sp. nov. (Potiguar Basin, Rio Grande do Norte State); green, Plakinastrella globularis sp. nov. (off Salvador, Bahia State and Almirante Saldanha Seamount, Rio de Janeiro State). The states where the new species occur are labeled: RN, Rio Grande do Norte; BA, Bahia; RJ, Rio de Janeiro.

FIGURE 5. Plakinastrella globularis sp. nov.: A, holotype (MNRJ 5980) preserved in ethanol; B, tangential section of the ectosome; C, transverse section of ectosome and choanosome; D, ectosomal palisade of small diods.

FIGURE 6. Spicules of Plakinastrella globularis sp. nov. (SEM): A, small diods; B, large diods; C, triods; D, calthrops; E, Microrhabds; F, spheres.