Plakortis potiguarensis, 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 : 536-538

Plakortis potiguarensis sp. nov.

( Fig. 4 )

Specimens examined (1). Holotype: UFPEPOR 585, Urca do Tubarão, Potiguar Basin, Rio Grande do Norte State, Brazil, 8 m depth. Fernando Moraes coll., 0 3 March 2007.

Specimens examined for comparison. P. angulospiculatus : UFRJPOR 3900, 4791, Fernando de Noronha Archipelago, Brazil. UFRJPOR 4032, Tamandaré, Pernambuco State, Brazil. UFRJPOR 4116, 4118, Carrie Bow Key, Belize.

Plakortis hooperi QMG 312880. Papua New Guinea.

Plakortis insularis : UFRJPOR 3917, 4803; MNRJ 2126, 2138; all from Fernando de Noronha Archipelago, Brazil

Plakortis microrhabdifera : MNRJ 2165, 2170, 2940, all from Atol das Rocas, Brazil.

Plakortis petrupaulensis sp. nov. MNRJ 11828, 11817, 11826, 11839; all from São Pedro e São Paulo Archipelago, Brazil.

Plakortis spinalis sp. nov.: MNRJ 8597, Sapata Cave, Fernando de Noronha Archipelago, Brazil.

Diagnosis. Color brown with gray and beige patches; skeleton with spicules in low density and disorganized in both the choanosome and ectosome, where some parts can show a tangential ectosomal reticulation. Spicules are smooth, irregular diods and triods and non-tuberculate microrhabds.

Description. Shape thick encrusting, 3.5 x 3.5 cm wide by 1 cm thick ( Fig. 4 A). External color is brown with gray and beige patches, remaining after fixation in ethanol. Internal color is light brown in vivo and after preservation. Surface smooth. Oscules after fixation circular, contracted, 1 mm in diameter, flush with the surface or slightly elevated, with lighter rims. Consistency cartilaginous.

Skeleton. Ectosomal skeleton generally disorganized ( Fig. 4 B) but with a relatively well-defined singlemeshed reticulation in some portions, with meshes 12-39-62 µm in diameter ( Fig. 4 C). Choanosomal skeleton scarce, disorganized, with no traces of reticulation. The ectosome is slightly darker than the choanosome ( Fig. 4 D). Apart from this, ectosomal specialization and subectosomal lacunae are absent. Canals are abundant in the choanosome.

Spicules. Diods slightly sinuous, irregular, with central bent well-marked and acerate endings ( Fig. 4 E, top): 32-71-89 / 1-2-3 µm (n=20).

Triods with irregular, sinuous actines and endings acerate or rounded ( Fig. 4 E, bottom): actines 22-28-32 / 1-2- 3 µm (n=20).

Microrhabds highly sinuous, irregular, some of them s-shaped, but never tuberculate ( Fig. 4 F): 4-10.7-25 / 1- 1.5-2 µm (n=20).

Spheres absent.

Habitat and ecology. Specimen collected at 8 m depth, on a calcareous vertical wall, without associated macrofauna.

Distribution. Endemic from Potiguar Basin, Rio Grande do Norte State, NE Brazil ( Fig. 1 ).

Taxonomic remarks. Plakortis potiguarensis sp. nov. is another species of the group of Plakortis with microrhabds, which also includes P. lita , P. microrhabdifera , P. hooperi , P. myrae , P. spinalis sp. nov. and P. petrupaulensis sp. nov. Of these, the most similar is P. hooperi , from Papua-New Guinea, which also has ectosomal and choanosomal skeletons disorganized, diods, triods, and non-tuberculate microrhabds (Muricy 2011). However, in contrast to P. potiguarensis sp. nov., Plakortis hooperi is thinly encrusting and has subectosomal lacunae, a denser skeleton, larger diods (79–148 µm long), and smaller microrhabds (2–8 µm long). Plakortis petrupaulensis sp. nov. differs from P. potiguarensis sp. nov. by a lighter color, absence of triods, and presence of tubercles on microrhabds. Plakortis myrae and P. microrhabdifera differ by the light brown color and especially by the reticulated skeleton, both in the choanosome and the ectosome (Muricy & Moraes 2003; Ereskovsky et al. 2013). Plakortis lita is dark brown or black and has a well-defined ectosomal tangential reticulation (de Laubenfels 1954; Muricy 2011).

Plakortis insularis is similar to Plakortis potiguarensis sp. nov. in the thick encrusting shape, brown color, absence of ectosomal and subectosomal lacunae, both ectosomal and choanosomal skeleton disorganized and with low density, and thin diods and triods (Moraes & Muricy 2003). It differs from the new species by a very soft and fragile consistency, release of a brown exudate in ethanol, and especially by the absence of microrhabds. Plakortis potiguarensis sp. nov. differs from all other species of Plakortis by the presence of non-tuberculate microrhabds.

Etymology. The name potiguarensis refers to the type locality, Potiguar Basin.

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 4. Plakortis potiguarensis sp. nov.: A, preserved holotype (UFPEPOR 585); B – C, tangential sections of ectosomal skeleton; D, transverse section of ectosome and choanosome; E, diod (top) and triod (bottom); F, non-tuberculate microrhabds (E – F, SEM).