Plakortis albicans, Cruz-Barraza, José Antonio & Carballo, José Luis, 2005

Cruz-Barraza, José Antonio & Carballo, José Luis, 2005, First record of Plakortis Schulze (Porifera: Homosclerophorida) from the Northeast Pacific coast, with the description of Plakortis albicans sp. nov., Zootaxa 868, pp. 1-12 : 4-9

Plakortis albicans sp. nov.

M aterial examined. Holotype MNCN 1.01/353, Isla Lobos (Mazatlán, Sinaloa, México), 23º13’49’’N – 106º27’43’’W, 4 m depth, 03/20/2002, under rocks. Paratypes: BMNH: 2004.11.2.1, Isla Lobos (Mazatlán, Sinaloa, México), 23º13’49’’N – 106º27’43’’W, 2 m depth, 11/16/2004, under rocks. LEB­ICML­UNAM­456, Isla Lobos (Mazatlán, Sinaloa, México), 23º13’49’’N – 106º27’43’’W, 4 m depth, 20/03/2002, under rocks. LEB­ICML­ UNAM­1063, Isla Lobos (Mazatlán, Sinaloa, México), 23º13’49’’N – 106º27’43’’W, 3 m depth, 01/28/2004, under rocks. LEB­ICML­UNAM­1100, Isla Lobos (Mazatlán, Sinaloa, México), 23º13’49’’N – 106º27’43’’W, 3 m depth, 04/01/2004, under rocks.

Diagnosis. White to ivory thickly incrusting Plakortis , sometimes with small purple patches with a surface sculptured with drainage subectosomic canals visible to the naked eye. Abundant diods in only one size class (12–137.5 µm long), triods always present, less frequent than the diods.

Description. Thickly incrusting sponge from 1 to 4 mm in thickness, covering a maximum area of 9 cm in diameter ( Fig. 2 a). The smallest specimens measure 1.5 by 1.2 cm ( Fig. 2 b). The consistency is slightly compressible but firm, and the surface is smooth and sculptured with very characteristic drainage subectosomic canals (60–132.8 µm in diameter), which are visible to the naked eye in situ ( Fig. 2 a, b), and in the preserved specimens. The surface is pierced by ectosomic pores of 18 to 50 µm in diameter, which are usually 10 to 25 µm apart. The canals converge on oscules, which are circular­shaped, 150 µm to 3 mm in diameter, and slightly elevated from the surface. Color in life is white to ivory, sometimes with small purple patches. The color is preserved in spirit, but it turns paler. The specimens were always collected under rocks.

Spicules. The diods are very abundant; they are irregularly curved, sometimes bent one or two times near the middle of the shaft ( Fig. 3 a, 4a). The ends are asymmetrical, hastate or acerate. These diods are very variable in size, but only one size class is recognizable ( Fig. 3 a, 4a). They measure 12–137.5 µm long (64 µm in average), and 1.3–7.5 µm width (3.6 µm in average). Even though the triods are always present, they are less frequent than the diods. They are predominantly equal­angled, but they can also be irregular ( Fig. 3 b, 4b). The rays are mostly straight or slightly bent. The size of the rays is very variable, 6.3–47.5 µm long (23 µm in average) (Table 1).

Skeleton. The ectosomal skeleton is a tangential alveolar arrangement of spicule tracts of 10 to 25 µm width formed mainly by smaller diods. The spicules tracts form meshes with amplitude of 18.9 to 50 µm in diameter ( Fig. 5 a, b). The choanosomal skeleton is formed by a dense and relatively confused reticulation of spicule tracts, although a clear reticulation arrangement with meshes of 15 to 30 µm in amplitude is differentiated in some places ( Fig. 5 c, d). The choanosome has abundant canals, 50 to 100 µm in diameter.

Etymology. The specific name refers to its typical white color. Distribution and habitat. Isla Lobos in Mazatlán Bay (Sinaloa, Mexico, east Pacific Ocean) ( Fig. 1 ). The specimens were collected in shallow water of 1 to 6 m depth and always under rocks.

Figures

FIGURE 1. Location of the collection sites of PLAKORTIS ALBICANS sp. nov. in Mazatlán Bay (Pacific Ocean, Mexico).

FIGURE 2. External morphology of Plakortis albicans sp. nov .. The arrows show the oscules A) Photograph of a large specimen taken at 5 m depth.; B) Photograph of a small specimen taken at 3 m depth where is clearly visible the characteristics drainage subectosomic canals.

FIGURE. 3. SEM images of the skeletal material of Plakortis albicans sp. nov. A) Diods; B) Triods.

FIGURE 5. SEM images of skeletal structure of Plakortis albicans sp. nov. A) Tangential view of ectosomal alveolar skeleton; B) Detail of the ectosomal alveolar skeleton; C) Cross section of choanosome; D) Detail of an aquiferous space.